12. Avian Resources of the Northern Gulf of Mexico

The habitat types available on barrier islands and mainlands include sandy beaches, salt marshes, brackish marshes, freshwater marshes, shrub/scrub, and forests. The National Land Cover Database (2006) has several categories of interest for birds. Maps showing the habitats in each state are presented in Appendix A. In this chapter, they were combined into 11 categories. Most are self-explanatory, but barren land includes rock, sand, and clay, some of which are used by many beach-nesting birds. The three forest types (deciduous, evergreen, mixed forest) were combined (Appendix A). The relative amount of habitat available in each state is shown in Figure 12.5 (10 mile area from the coastline). Texas has a high percentage of woody wetlands, forests, and developed land. Louisiana has the greatest percentage of its coastal area as water and wetlands. Mississippi has mainly open water and wetlands, while Alabama (with the smallest coastal band) has primarily forest and woody wetlands. Florida, with the greatest coastal area, has mainly woody wetlands, developed land, and forests along its coast (Figure 12.5).

Birds have generalized niche requirements that relate to habitat availability. The open waters of the Gulf of Mexico are pelagic, and species living there are normally seabirds and some diving ducks. While winds, currents, and temperatures control the pelagic environment, the landward environments are ruled by tides. Tidal marshes are found in small, narrow pockets along coastlines, with the main vegetation being Spartina and Juncus spp. (Greenberg et al. 2006). The combination of salinity, low floristic and structural complexity, regular tidal fluctuations, catastrophic flooding, and high winds in tidal marshes creates a vulnerable, unpredictable environment, requiring flexibility and adaptability on the part of the birds living there (Greenberg et al. 2006). While tidal marshes support relatively few unique or endemic species of terrestrial vertebrates, some subspecies have differentiated (Greenberg et al. 2006), such as the Louisiana Seaside Sparrow (Ammodramus maritimus fisheri) (Gabrey and Afton 2000). Although birds exhibit flexibility in their choice of nesting sites, they prefer particular types of habitats (Wilson and Vermillion 2006). Gulls, terns, skimmers, and shorebirds nest on the ground, usually on bare sand or in places with sparse vegetation, or they build nests in marshes. Pelicans nest on bare ground or in vegetation that is sparse, but tall enough to allow them to maneuver their large bodies underneath it. Herons, egrets, and ibises prefer to nest on low vegetation, particularly in the Gulf, but will sometimes build nests on the ground or in shrubs and trees. Ducks, Willet, and Clapper Rail build nests low in the vegetation or on the ground, usually in marshes. Snowy Plovers and Oystercatchers build nests on open, unvegetated sand, relying on being cryptic to camouflage their eggs. Sparrows and some other songbirds nest in marshes, scrubs, or forests (Moore et al. 1990; Buler and Moore 2011).

A schematic of nesting preferences is shown in Figure 12.6. Wintering birds also have preferred habitats. Figure 12.7 indicates the likely zonation of birds in the winter, which mainly reflects foraging and roosting sites. Habitat use is generally wider during this period as they are not restricted to nest sites.

Habitat suitability refers to whether a given habitat is usable (or suitable), considering physical, vegetative, and social features, within a context of anthropogenic factors. It is essential to distinguish both interspecific differences and those due to activities (breeding vs. migrating or overwintering; nesting vs. foraging). In the nesting season, birds are tied to their nest site during the incubation period, and non-precocial species are limited to the nest site during much of the chick-rearing phase. The chicks of precocial species (ducks and rails) are able to locomote and search for food shortly after hatching. Chicks that are not precocial (altricial) must be brooded early on because they have no feathers and cannot regulate their body temperature. They are guarded and fed until they are able to forage on their own. This imposes constraints on birds to select nest sites that are removed from the threat of tides, floods, inclement weather, and predators.

A data set for Louisiana-Alabama provides an overview of habitat use by colonial-nesting species (Portnoy 1981). Habitat preferences for common birds normally considered coastal are shown in Figure 12.8 (none with populations below 500). Most of the Plegadis species were White-faced Ibis (Plegadis chihi). This data set, because it encompassed colonies in three states, can be used to infer habitat preferences (layered upon habitat availability). The patterns reflect choices before the rapid coastal and offshore development of the last 35 years. The Brown Pelican is the only species for which the data are not typical. Because of its sharp decline in the 1950s and 1960s due to pesticides, it had not yet recovered (Wilkinson et al. 1994; Shields 2002). A similar survey in 2001 indicated that 40 % of the active pelican colonies were in saline marshes, 24 % were in freshwater marshes, 22 % were in forested wetlands, and the remainder in scrub, shrub, upland forest, or brackish marshes (Michot et al. 2003).

Figure 12.8 provides a picture of horizontal nesting stratification from the Gulf landward. Most terns and Laughing Gulls nested on bare sand, and most skimmers nested on sand; although, a few nested in salt marshes. Skimmers and Laughing Gulls sometimes are forced to nest in salt marshes because of competition with other species, lack of available beaches, or human disturbance (Burger and Gochfeld 1990). Forster’s Terns always nest in marshes (McNicholl et al. 2001).

Habitat use for nonbreeding birds is a function not only of habitat structure and vegetation types but also of prey types and foraging methods. Seabirds capture prey by a variety of methods, including plunge-diving for fish or invertebrates, surface-plunging, hop-plunging, hover-dipping, and picking food items off the surface of water, although gulls and some other seabirds pick up fruit or insects from the ground, follow boats, scavenge on offal along the shore, pirate food from other seabirds, and forage at landfills (Ashmole 1971; Sealy 1973; Burger and Gochfeld 1981; Shealer 2001). In the Gulf, gulls, terns, and skimmers forage in pelagic waters, shallow tidal creeks, and behind boats or near other human activities, as well as at landfills (garbage dumps), inland lakes, and impoundments (Burger 1987a, 1988a; Burger and Gochfeld 1983a; Patton 1988). Ducks breed mainly in marshes or in distant uplands, but spend the winter in coastal areas or in nearshore environments. Some ducks form large flocks on the water and forage on the open sea (diving ducks), while others feed at the marine-land interface in bays, estuaries, marshes, fields, and other terrestrial habitats (dabbling ducks). Herons, egrets, and ibises breed on islands and along coastal areas, and feed in intercoastal habitats; they do not feed in open water as most forage while standing. Shorebirds feed along the shoreline on the mainland, along barrier islands, or around offshore islands. Their feeding method of picking up items from the sand, from shallow water, or along wrack lines, ties them to the narrow band along the shoreline.

Species diversity varies within close habitats, partly as a function of time of day, tide stage, and tide height (Withers 2002). Habitat use can be examined by season, particularly for beach habitats where birds forage and roost throughout the year, as well as during migratory stopovers. Chapman (1984) examined seasonal use of beaches on Padre and Mustang Island barrier beaches (Figure 12.9).

This figure shows the relationship among species groups by season. Shorebirds made up the largest component in the spring, fall and winter, while gulls made up the largest component in the summer.

The flight abilities and inclinations to migrate or disperse are variable in birds. Seabirds are the most mobile, and are likely to fly the greatest distances from their nest sites to forage, and some circumnavigate the globe in the nonbreeding season. Many seabirds nest on offshore islands far removed from predators, such as Campeche Bank off the Yucatán (Tunnell and Chapman 2000), or on the Dry Tortugas (Dinsmore 1972), and show very high nest and colony site fidelity. Seabirds that nest on less stable coastal islands shift colony sites as conditions dictate, but have high site fidelity if colony sites remain unchanged (Buckley and Buckley 1980; Coulson 2001).

Pelicans, herons, egrets, and ibises that nest in coastal colonies use the same sites as long as they remain safe from predators and are suitable. For many species, nest site requirements drive their choice of colony site, and they will continue to nest there if the sites remain stable. In some cases, long-term stability is enhanced by habitat modification, as happened on Queen Bess Island for pelicans (Visser et al. 2005). In other cases, stability is reduced by erosion and loss of space.

For some species, choice of colony site is dependent upon foraging opportunities. Roseate Spoonbills depend upon periodic drawdown and flooding to produce pools with high prey availability (Kushlan 1979). While other herons and egrets also depend on such resources, the dependence is not as strong. White Ibis are more nomadic, both in foraging behavior and in nesting behavior (Frederick et al. 2009). They also require dry down and the concentration of suitable prey (Frederick et al. 1996). The combination of nesting and foraging habitat requirements leads to shifting colony locations for these species, and they may move hundreds of kilometers between different years. Other species are quite sedentary and are not likely to fly long distances. This has the effect of isolating populations, which can lead to subspecies. For example, Seaside Sparrows living along the Gulf are resident and do not fly long distances. Separate populations can become isolated, and if they disappear recolonization is unlikely unless there is a population nearby to provide founders (individuals to colonize).

Common Loons are large, long-lived birds with delayed maturity and low fecundity. They nest on small isolated islands in lakes in the northeastern United States and Canada. They are awkward on land, have webbed feet, are superb swimmers, and dive for fish. Their breeding range is restricted to mainland North America (Evers et al. 2010). They nest from Washington to Montana, to northwest Wyoming, north-central North Dakota, and the upper Great Lakes, and from New York to New England (Evers et al. 2010). They winter on the Pacific and Atlantic coasts, including the Gulf of Mexico and the Gulf of California. Common Loons in Mexico winter off the Texas coast (Howell and Webb 1995). They rarely winter farther south of central Mexico; some remain as far north as Newfoundland and the Aleutian Islands of Alaska (Evers et al. 2010). They also breed in Greenland, Iceland, and Northern Eurasia, and winter from the southern coast of Norway and Sweden south to the Caspian and Black Sea, China, and Formosa (Stevenson and Anderson 1994). In winter they are white below with dark gray upperparts (Figure 12.10).

Common Loons are used as indicators of environmental health in the northeast because of documented effects from acid rain and mercury (Burger et al. 1994; Nocera and Taylor 1998; Burgess et al. 2005; Burgess and Meyer 2008; Evers et al. 2008). They also are useful indicators in the Gulf of Mexico because they swim on the surface and dive for relatively large fish that are 10–15 cm long or more (Imhof 1962). Acid rain increases biomethylation of mercury in cold water, and methylmercury accumulates in fish. On the breeding grounds, mercury continues to build up in tissues as the Loons age, and increasing body burdens reduce the number of young fledged per pair (Evers et al. 2008). While they usually occur inshore, they can also range up to 100 km out into open Gulf waters (Evers et al. 2010), making them vulnerable to oceanic and Gulf coast pollutants.

Common Loons breed on small to large lakes, nesting near the edge of isolated small islets devoid of predators (Vermeer 1973a; McIntyre 1988; Barr 1996). Loons usually lay two eggs, but only fledge one chick (McIntyre 1988). Loons arrive on the northern coasts of the Gulf of Mexico by the third week of October, mainly from Minnesota and Wisconsin (Evers 2004), and numbers build up until mid- November (Alexander 1991). Mortality in Loons is due to mercury contamination, commercial fishing (Vermeer 1973b), botulism (Brand et al. 1983), and nutritional stress from high costs of plumage replacement in winter (Alexander 1991), among other factors.

Common Loon populations are probably stable to increasing in the United States (Evers et al. 2010), and the United States and Canadian population is estimated at 607,000–634,000 birds (Delany and Scott 2006). Using Christmas Bird Counts for the entire U.S. Gulf coast, Niven and Butcher (2011) computed a significant 1.6 % per year increase over the period from 1965 to 2011. Imbedded in this increase was a decrease in numbers and reproductive success in the 1980s and 1990s, partly from acid rain and mercury (Evers et al. 2010). Using the same Christmas Bird Count data, running 3-year averages were computed for Common Loon numbers from 1940 to the present (Figure 12.11). There is variation along the Gulf, with few birds recorded from Mississippi, Louisiana, and Texas, and the majority recorded off the coast of Alabama and Florida. The data show a peak in the 1980s, with a recent increase in Alabama and a decline in Florida.

Resiliency in Common Loons is low because of low clutch size (two eggs), low reproductive rate (usually raise one or fewer young per year), high mortality while at sea the first 2–3 years of life, and delayed breeding age (average age of 6 years; Evers et al. 2010). Although the loon has a long life span of around 30 years (Evers et al. 2010), it is susceptible to mercury poisoning because it eats large fish on the breeding grounds of lakes where prey fish accumulate high mercury levels (Evers et al. 2008).

Pelicans are very large, plunge-diving birds with recognizable gular pouches. They nest colonially along the Pacific, Atlantic, and the entire Gulf coasts (Figure 12.12). These iconic birds only breed along coasts, and their image is put on placemats, postcards, billboards, and signs throughout the Gulf (Eubanks et al. 2006). Their breeding range is along the Pacific coast from southern California to southern Ecuador (including the Galapagos), and along the Atlantic coast from Maryland south, around the Gulf of Mexico and Caribbean coast, to northern Venezuela and Colombia (Shields 2002).

Brown Pelicans feed on small fish (10–28 cm long), such as Menhaden (Brevoortia patronus) (Imhof 1962; Hingtgen et al. 1985), a major commercial fish in the Gulf. Fishermen have persecuted them because they were believed to eat commercial fish (Sprunt 1954). Pelicans dive with the bill ajar, and the force of water on impact causes the pouch to expand, trapping the fish inside. The Pelican then raises the bill above the water, pointed downward, and the water runs out, leaving prey in the pouch (Stevenson and Anderson 1994). Pelicans usually feed within 20 km of the nest site (Briggs et al. 1981), indicating the importance of having suitable nesting colonies near foraging opportunities.

Current population estimates for Brown Pelicans (P.o carolinensis) are 44,000–45,000 pairs; about 60 % of the 40,000 that nest in the United States do so along the Gulf Coast (Shields 2002). Pelicans are resident in most of their breeding range (Shields 2002). Pelicans breed in monospecific and mixed-species colonies, often with other ground-nesting species. They use the same colony site in successive years unless it becomes unsuitable because of habitat loss, human disturbance, or predators (Schreiber and Schreiber 1982). Colony site selection in pelicans depends upon the availability of nest sites that are free from predators and human disturbance, and are reasonably close to food. Colonies in Louisiana averaged 13 km from the mainland (Visser et al. 2005). Brown Pelicans are monogamous, mate for life, lay up to five eggs, and the young are fed predigested fish that parents deposit on the nest.

Brown Pelicans exhibited one of the most dramatic population declines ever observed in birds, which occurred between the late 1950s and the early 1970s, due to the organochlorine pesticide DDT (Shields 2002). Before the decline, populations in Louisiana and Texas were estimated at greater than 50,000 birds (Shields 2002). Lowery (1974) claimed that before the decline, most Brown Pelicans seen along the entire northern Gulf coast were produced in Louisiana. Pelicans declined from about 5,000 individuals in Texas in the early 1960s, to fewer than 20 individuals by 1974 (King et al. 1977). Populations disappeared in other places, and reintroductions were necessary. The mechanism of decline was through eggshell thinning caused by DDT; pelicans that incubated broke their eggs (Blus et al. 1974).

Brown Pelicans were reintroduced into Louisiana at Queen Bess Island in 1971 and the Chandeleur Chain in 1979 (Wilkinson et al. 1994). Before 1983, no Brown Pelicans nested in Alabama; the first ones were relocated there in 1983, and by 1990 there were 1,374 nests (Wilkinson et al. 1994). The Florida Gulf coast population of breeding Brown Pelicans declined, but remained stable in Tampa Bay after the 1990s (Hodgson and Paul 2010), while the Atlantic coast population increased (Wilkinson et al. 1994).

Trends in breeding populations have been examined in many places. Two examples are given: Queen Bess Island in Louisiana, and Galveston Bay in Texas. Breeding populations at three sites in Louisiana were followed from 1971 (when numbers had declined drastically from DDT) to 1993 (Figure 12.13, after Visser and Peterson 1994). Pelicans were locally extirpated in Louisiana and were reintroduced at Queen Bess Island in the early 1970s (Holm et al. 2003). Subsequently, when numbers declined at Queen Bess, they increased at a nearby colony. Lindstedt (2005) reported the number of successful nests at Queen Bess and Last Islands after 1993 (Visser and Peterson 1994), and showed a small decline in the mid-1990s (Figure 12.13). Pelicans in Louisiana increased in these colonies from about 2,000 nests in 1990 to stabilize around 15,000 nests in 2003 (Holm et al. 2003; Visser et al. 2005). Pelican colonies in Louisiana are located far from the mainland and human activity, and colonies such as Queen Bess Island have required the addition of land to provide sufficient habitat (Visser et al. 2005).

Surveys of Brown Pelicans nesting in Galveston Bay, Texas, have also been made for a number of years. The number of nesting pairs has been increasing there although there were large shifts in the number of nesting pairs (Figure 12.14). The Galveston Bay Status and Trends report rated the species, used as an indicator by the program, as good—significantly increasing (GBEP 2006).

Brown Pelicans are reaching population levels on the Gulf Coast of North America that were present before the widespread use of DDT (Robinson and Dindo 2011). Pelicans are faced with severe habitat loss that might threaten their populations once again, particularly in Louisiana due to loss of available nesting sites (Visser et al. 2005). Robinson and Dindo (2011) comment that the future of Brown Pelican populations in the Gulf is unclear because of the ephemeral nature of spoil islands and natural coastal areas, as well as natural disasters, and manmade ones. Periodic reproductive failures have little effect on population levels, but recurrent breeding failures result in population declines (Schreiber 1980a). Another cause of mortality is exposure to cold and storms, hypothermia, frostbite damage to gular pouches and foot webs, starvation, and longer-term cold weather effects on breeding phenology (Schreiber 1980b; Shields 2002). Therefore, changes in temperature because of global warming could increase populations of Brown Pelicans in the northern coast of the Gulf of Mexico.

Another cause of mortality in Brown Pelicans, unlike most other indicators, is from people. A study of 3,106 recoveries of Brown Pelicans banded in the Carolinas and Florida, from 1925 to 1983, indicated that more than half died from human activity, with entanglement in fishing lines as a major cause (Schreiber and Mock 1988). Pelicans are sometimes killed or maimed maliciously.

Shields (2002) plotted recovery of Brown Pelicans along the Gulf Coast as a whole, showing a steady rise in nests from the 1970s through the 1980s, with greater increases thereafter (Figure 12.15). The number of nesting Pelicans did not increase as sharply along the Atlantic coast, or along the California coast; populations in California fluctuated around 5,000 pairs since the mid-1980s (Shields 2002).

Resiliency is relatively high as evidenced by their population recovery following devastation by pesticides in the 1950s and 1960s. Pelicans reach sexual maturity at 3–5 years of age, lay up to five eggs (modal clutch is three), usually fledge one or fewer chicks, only 30 % survive the first year, and fewer than 2 % survive beyond 10 years (Schreiber and Mock 1988; Shields 2002). They probably have only an effective reproductive life span of 4–7 years although they can live for 25–30 years (Schreiber and Mock 1988). Since human disturbance and breeding habitat availability seem to be major problems, recovery from any declines will partly depend on these factors.

The dazzling white plumage of Great Egrets, with their long lethal yellow bill, and their motionless stance as they wait to capture prey, makes them easy to recognize (Figure 12.16). Great Egrets are cosmopolitan, inhabiting freshwater, estuarine, and marine wetlands, and are intermediate in size between the larger Great Blue Heron and the smaller egrets. Great Egrets breed in North and South America, in southeast Europe, northern Asia to Siberia, north China, and northern Japan, as well as in Australia (McCrimmon et al. 2011). In North America, they breed primarily along the Atlantic Coast from Maine south to all regions along the Gulf coast, to the east coast of Mexico, and down to South America, including the Caribbean Islands. On the west coast they breed in California, and on the west coast of Mexico and Central America. They also breed in scattered inland areas in the Central United States (McCrimmon et al. 2011). They winter throughout their breeding range, except for interior North America and the northeast coast (McCrimmon et al. 2011).

Egrets are useful indicators for the Gulf Coast because they are colonial, conspicuous (large and white), usually nest higher in vegetation when it will support their nests, and are key members of wading bird nesting assemblages in the coastal regions all along the Gulf of Mexico, including Mexico (Burger 1978a; Mock 1978, 1980). They feed on intermediate-size fish, as well as reptiles, amphibians (especially frogs), small mammals, birds, crustaceans, mollusks, and insects (Stevenson and Anderson 1994). They also visit inland rice fields, crawfish ponds, and wet fields to find frogs, as well as dry fields to stalk small reptiles (Eubanks et al. 2006).

Great Egrets nest in mixed-species colonies with other egrets, herons, ibises, and often Brown Pelicans. These colonies are stable as long as conditions remain viable and the habitat suitable; otherwise they switch sites (Kelly 2006a). They are monogamous, and both parents incubate and care for the young, including provisioning (McCrimmon et al. 2011). Incubation (28–29 days) begins with the first or second egg so that young hatch asynchronously; when food is in short supply, competition between siblings results in older chicks kicking eggs or younger chicks out of the nest (Mock and Lamey 1991; Stevenson and Anderson 1994).

Great Egret populations, along with other herons and egrets, declined dramatically in much of the United States during the late 1800s and early 1900s due to hunting their plumes for the millinery trade (Ogden 1978). Their plumes (called aegrettes), used in courtship displays, have a delicate, lacey appearance (Figure 12.16). The North American population of Great Egret declined by more than 95 % with market hunting (McCrimmon et al. 2011). Populations quickly recovered with the passage of the Migratory Bird Treaty Act in 1913, and they once again moved into breeding areas in the Northeast where they had largely disappeared (Burger 1996b; McCrimmon et al. 2011). The North American population is currently estimated at about 270,000 birds (Delany and Scott 2006). The nesting population of Great Egrets along the western Gulf coast increased from the 1930s to the 1990s. For example, numbers in Louisiana were 2,900 pairs in 1959, 11,000 pairs in 1974, and 29,000 pairs in 1990; Texas, had 5,000 pairs in 1939, 1,450 pairs in 1959, and 6,500 pairs in 1969 (McCrimmon et al. 2011).

Trends data from Shamrock Island in Texas indicate that the number of Great Egret pairs varied markedly from almost zero in 1973 to more than 160 pairs in 1999 (Gorman and Smith 2001), and thereafter numbers increased (TCWS 2012). However, there is now evidence from south Florida that numbers have declined (Figure 12.17).

Using Christmas Bird Counts (1965–2011) as a database, Niven and Butcher (2011) reported that wintering Great Egret showed a significant increase of 2.1 % per year in coastal U.S. Gulf counts. Furthermore, when Fleury and Sherry (1995) used Christmas Bird Count data to examine the effects of crayfish aquaculture on Louisiana birds, they found that Great Egrets also increased significantly from 1949 to 1989. Using Christmas Count data for all states combined also shows an increase (Figure 12.18). Using Breeding Bird Survey data, Sauer et al. (2005, 2008) shows a steady but small increase in the Great Egret population nationwide.

Great Egrets have fairly high resiliency because they were able to recover from the devastation of plume hunting. They breed when they are 1–3 years old; clutch size varies from 1 to 6; average hatching rate is about 60 %, most commonly fledge between 0.5 and 1.5 chicks per nest; and between 40 and 75 % of nests in a colony are successful (McCrimmon et al. 2011). Success can vary; Parsons and Burger (1982) reported a hatching rate of 97 %, but a fledging success of only 50 % in a Louisiana colony. These parameters do not apply if the colony is harassed, food is scarce, or they suffer hunting or other external stressors.

Reddish Egrets are the rarest species of heron in North America. They have a rather shaggy appearance because of the feathery plumes on both the head and back (Figure 12.19). They breed in coastal wetlands on both coasts of Florida (except in the Panhandle), Gulf of Mexico from Louisiana to south Texas and into Tamaulipas, along the Yucatán peninsula, in the Caribbean and Bahamas, and sporadically along Baja California and the Pacific coast of Mexico (Lowther and Paul 2002). The first Reddish Egret bred in Louisiana on North Island in the Chandeleur Sound in 1958 (Lowery 1974). They are resident in their breeding range, but following breeding, some birds spread out on the east coast of Mexico, down to Costa Rica and Belize, and all along the Pacific coast of Baja California and of Mexico into Central America (Lowther and Paul 2002). Significant wintering flocks can be found in the Laguna Madre in Texas and Mexico (Eubanks et al. 2006).

Reddish Egrets are of particular interest because (1) the Gulf of Mexico plays a key role in their breeding and resident distribution; (2) they are a species of special concern by the U.S. Fish and Wildlife Service (USFWS) (Bates et al. 2009); (3) they are a species of moderate concern as evaluated by the U.S. Shorebird Conservation Plan (Elliott and McKnight 2000), as well as the Southeast U.S. Regional Waterbird Conservation Plan (Hunter et al. 2006); (4) they are a priority species for habitat planning by the Gulf Coast Joint Venture (Vermillion and Wilson 2009); (5) their populations were greatly impacted by plume hunting and their populations never recovered (Paul et al. 1975; Lowther and Paul 2002; Hunter et al. 2006); and (6) they are extremely coastal. They are mainly residents, although some withdraw farther south in the Gulf of Mexico in winter (Turcotte and Watts 1999; Lowther and Paul 2002).

Reddish Egrets forage only in coastal habitats where they can appear both comical and elegant when foraging. They hunt by running, hopping, flying, and employing open-wing antics as they pursue small fish, although they sometimes stand and wait for prey. Reddish Egrets mainly forage in shallow pools where fish and invertebrates are concentrated by cyclic flooding and drying (Powell et al. 1989).

Reddish Egrets typically nest in bushes or trees in mixed species colonies along the coast and on coastal islands, and they forage in shallow, salt-water habitat (Lowther and Paul 2002), making them vulnerable to any coastal threats (Toland 1999). They also nest on dredge spoil islands (Toland 1999). They sometimes breed in small groups, and very rarely, as isolated pairs (FFWCC 2003).

In the 1950s, Reddish Egrets in Florida were limited mainly to the Keys, and wildlife managers experimented with transferring eggs from Texas to place them in heron nests (Sprunt 1954). Only in the last 30 years have Reddish Egret populations begun to increase in Florida Bay enough to spread up the Gulf Coast on their own (Paul et al. 1975; Powell et al. 1989). Currently, about 2,000 breeding pairs are in the United States, and 75 % of the U.S. population resides in Texas (Lowther and Paul 2002; Bates et al. 2009). The Bahamas are an important site for Reddish Egrets (Moore and Gape 2008), although surveys there indicate more than a 50 % decline in numbers since the 1980s (Green et al. 2011), which is a cause for concern. Because of their limited range, nonmigratory pattern, and colonial nesting, populations can be estimated. The breeding populations for the Gulf states are as follows: Texas 900–950 pairs, Louisiana 60–70 pairs, Alabama 5–10 pairs, and Florida 350–400 pairs, for a total of 965–1,030 pairs (>39 % of global population) (Lowther and Paul 2002; Green 2006). No Reddish Egrets breed in Mississippi. Lowther and Paul (2002) previously estimated the U.S. population to be about 2,000 pairs, but current estimates are 3,000–5,000 breeding pairs (Delany and Scott 2006). Populations are subject to considerable yearly variation. If their Gulf habitats are rendered unusable, Reddish Egrets have nowhere else to go since they are strictly a coastal species (Vermillion and Wilson 2009). Conservation concern led the Gulf Coast Joint Venture Conservation waterbird working group to designate several sites as high priority for Reddish Egret (Vermillion and Wilson 2009). These sites are centered on the south Texas coast; the waterbird working group believes they can increase breeding populations at some of these colonies by 25 %.

There are few trends data for Reddish Egrets from the Gulf States. Gorman and Smith (2001), however, tracked populations at Shamrock Island in Texas from 1973 to 1999 (Figure 12.17). While this is only one colony, it provides information on trends and variability in that colony. Reddish Egret numbers generally increased from 1973 to 1999, although the numbers were quite variable. After 1999, the numbers seemed to increase (TCWS 2012). In contrast, in Tampa Bay the numbers remained low and constant at about 100 breeding pairs (Hodgson and Paul 2010).

Fleury and Sherry (1995) used Christmas Bird Counts (1949–1988) to examine long-term population trends in Louisiana and found that populations of Reddish Egret increased 3 % per year over the 40-year period. However, from 1980 to 1988 they declined by 11.4 %. Niven and Butcher (2011) using Christmas Bird Counts for the entire U.S. Gulf coast computed a 1.6 % per year increase over the period from 1965 to 2011. A 3-year running average of Christmas Bird Count data over a longer period was computed (Figure 12.20). Variability was much greater in Texas, particularly in three time periods (early 1950s, early 1990s, and 2004–2006), which bears further examination. While Niven and Butcher (2011) show an overall increasing trend from 1965 to the present, it is not a clear consistent pattern.

Resiliency in Reddish Egrets is low as evidenced by its slow recovery from the devastation of plume hunting, particularly in relation to other egrets that recovered quickly. Most breed in the fourth year, clutch size is usually three eggs, and the maximum longevity from banded bird studies is just over 12 years.

Roseate Spoonbills are stately, delicately pink birds with a greenish, flattened bill that move slowly through the water, swinging their bill from side to side (Figure 12.21). They are neotropical birds whose range extends northward to the southern United States, especially along the Gulf Coast. The main breeding area of Roseate Spoonbill is south of the United States, perhaps in Brazil (Hancock et al. 1992), and the main breeding areas in North America are along the coasts of Texas, Louisiana, and south Florida (from Tampa Bay south), with a few records from Louisiana (Dumas 2000). They rarely nest in Alabama and Mississippi. They breed sporadically along both coasts of Mexico, south to Argentina and Chile (Lewis 1983; Dumas 2000). They winter along both southern coasts of Florida, in the Gulf of Mexico, along both coasts of Mexico to Belize and Central America, and on the Pacific coast to South America (Dumas 2000). They disperse in the nonbreeding season, but mainly remain along the coasts of Louisiana and Texas, and rarely are sighted in Alabama and Mississippi (Turcotte and Watts 1999). The U.S. breeding population of this largely Gulf coast species is about 5,500 pairs, with another 3,230 pairs along the Mexican Gulf coast (Dumas 2000).

Spoonbills feed by tacto-location during day or night, at low tide (Hancock et al. 1992). While walking, they swing their slightly open bill from side to side; when it contacts prey, it snaps shut, mainly on fish, crayfish, shrimp, insects, and other aquatic invertebrates (Lewis 1983; Dumas 2000). Decline of the species in a specific area of the Gulf could be caused by loss of foraging habitat, although Spoonbills can move to other areas with suitable shallow pools for foraging.

Roseate Spoonbills nest in mixed-species colonies with other herons and egrets, although in some places they nest mainly with White Ibis (Imhof 1962). They prefer islands and keys without predator access. In a colony in Nueces Bay, Texas, they nested with Great Blue Herons, Great Egrets, Snowy Egrets, Cattle Egrets, Louisiana Herons, Black-crowned Night Herons, and Laughing Gulls (White et al. 1982), which is typical in other parts of their range. They nest low in trees or shrubs, including mangroves (Sprunt 1954; Portnoy 1977; Lewis 1983). Incubation requires 22–24 days (Lewis 1983), and the nesting season can be prolonged because nesting is not synchronous within a colony (Sprunt 1954). Postbreeding movements require more study, although some birds from Texas move a little south into Mexico (Dumas 2000), and birds from Florida move northward (Hancock et al. 1992).

Roseate Spoonbills, like many other wading birds, suffered virtual extirpation in the late 1800s to the mid-1930s because of harvesting for plumes and food. From 1865 to the late 1880s they were limited to small areas in Texas, Louisiana, and Florida (Imhof 1962). They were nearly extirpated by the late 1800s from the U.S. Gulf coast; their numbers declined to only 15 pairs during the end of the plume trade era (Rodgers et al. 1996). Spoonbill numbers gradually increased after protection from the Migratory Bird Treaty Act. They first began breeding in Texas in 1923, and Friedmann (1925) saw flocks of 75–100 feeding in shallow water and reported another flock of 1,000 feeding in southern Texas. They increased to 830 pairs by 1941 to 3,000 pairs in the 1970s, and then declined to 1,124 pairs in the 1980s (Dumas 2000). By 1996, they were up to 2,901 pairs (Dumas 2000). In Louisiana, numbers ranged up to 150 pairs in the 1940s, and then increased thereafter (while they decreased in Texas), with a 36 % increase from 1966 to 1989 (Breeding Bird Survey) (Dumas 2000). Data from Florida Bay indicated a steady increase in the number of Roseate Spoonbill colonies, and nests, but great variability among years (Figure 12.22) (Powell et al. 1989). There were fewer than 500 pairs in the 2000s (Lorenz et al. 2008). Thus their numbers appear to have declined. A recent review by the Florida Fish and Wildlife Conservation Commission (FFWCC 2011a) recommended that Roseate Spoonbills be given the status of threatened because populations are very small and restricted. Nesting colonies are affected by hydrological changes caused by management. For example, construction of canals in the Everglades reduced the flow of freshwater to the Florida Bay and decreased Roseate Spoonbills in the 1980s (Davis et al. 2005). Small fish are the primary food of Roseate Spoonbills in Florida Bay (Bjork and Powell 1994), and without a water depth threshold of 12 cm, fish are not sufficiently concentrated to provide adequate food reserves (Lorenz 2000). Thus, hydrology (salinity gradients, water depth, and dry-down) influences whether birds nest and also their reproductive success (Davis et al. 2005). Delany and Scott (2006) estimated that the number of Roseate Spoonbills in Florida and the West Indies was 3,400 individuals. Data from Shamrock Island in Texas indicated a variable, but generally stable trend from 1973 to 1999 (Gorman and Smith 2001). The number of breeding pairs varied from about 25–200 (Figure 12.23). Thereafter, numbers seemed to increase (TCWS 2012).

Using Christmas Bird Counts from 1965 to 2011, Niven and Butcher (2011) reported that wintering Roseate Spoonbills showed a significant increase of 5.9 % per year. Figure 12.24 shows populations from 1951 to 2001.

Resiliency may be low in the Gulf region because historical populations were believed to be higher prior to plume hunting, and Spoonbill populations have not recovered to those levels (Dumas 2000). They usually breed at 4 years, but may breed at 3 years of age, usually lay 3–4 eggs (up to 5) and average 1–2 young fledged per nest (but this varies considerably and often colonies fail completely). Little information is available on longevity (Lewis 1983; Dumas 2000). Reproductive success partly depends upon the availability of prey that is concentrated by drying down periods (Powell et al. 1989) and varies greatly from year to year (White et al. 1982).

Mottled Ducks, a southern relative of the American Black Duck (Anas rubripes) and the Mallard, breed in marshes and wetlands along the Gulf of Mexico (Bielefeld et al. 2010). They resemble female Mallards, except Mallard females have a blotched bill, a whitish tail, and a white border on the front and rear of the blue speculum (Figure 12.25). They are a non-migratory resident in the Gulf Coast of the United States and into northeastern Mexico (Tamaulipas) (Howell and Webb 1995). The two disjunct populations are from western Alabama to northeast Mexico (south to Tampico), and one isolated in Florida (Johnson 2009; Bielefeld et al. 2010). The Mottled Ducks in Florida migrate north in Florida in the winter (Stevenson and Anderson 1994).

Mottled Ducks occur in near-subtropical climates of the Texas and Louisiana Gulf coast where wetlands are not subjected to near freezing temperatures (Figure 12.25) (Grand 1992). Wetland drainage, degradation of coastal marshes by saltwater intrusion and urban development pose a risk, along with hybridization with Mallards. In the nonbreeding season they concentrate in fallow-flooded fields in Florida and in harvested rice fields in the western Gulf Coast (Figure 12.26) (Bielefeld et al. 2010).

The Mottled Duck prefers to feed in shallow, ephemeral wetlands (Swanson and Meyer 1977), which means they have a narrow range of habitat requirements for nesting. They feed on submerged vegetation in delta and saltwater marshes, on invasive species such as Eurasian Watermilfoil (Goecker et al. 2006), and snails and insects (Imhof 1962). They also feed on vegetation and animal matter (mollusks and crustaceans, insects) in Florida (Stevenson and Anderson 1994). In Mississippi, more than half of their diet is animal matter (insects, snail, fish, crustaceans), as well as rice, bulrushes, pondweeds, and other aquatic vegetation (Turcotte and Watts 1999). Their dependence on estuarine habitats requires further study, as Moorman et al. (1991) found that Mottled Duck ducklings died if salinity was much greater than 12 parts per thousand (ppt), and that the tolerance may be closer to 9 ppt. This suggests that management to enhance Mottled Duck populations should take salinity into consideration when creating impoundments. Mottled Ducks breed and winter at very low densities in the fringe of the Gulf of Mexico in coastal Alabama and Mississippi, and reach their highest densities in coastal Louisiana and southeast Texas, with smaller numbers south to Veracruz (Bielefeld et al. 2010). They nest in estuarine marshes, although they have been reported nesting in farm fields (Eubanks et al. 2006). Nests and eggs are vulnerable to a wide range of predators, including raccoons, skunks, opossums, dogs, and snake; turtles and alligators (Alligator mississippiensis) prey on ducklings (Stevenson and Anderson 1994), and in Texas, predators also include River Otters (Lutra canadensis), Striped Skunks (Mephitis mephitis), mink (Mustela visor), coyotes (Canis latrans), Red Fox (Vulpes vulpes), Gray Fox (Urocyon cinereoargenteus), and feral dogs (Canis familiaris), cats (Felis domesticus), and Snapping Turtles (Chelydra serpentina) (Bielefeld et al. 2010).

Half of the Mottled Duck populations in the United States reside in Louisiana (Lindstedt 2005). Estimated Mottled Duck populations in southeastern Louisiana increased until 1994 (peak of more than 100,000), and then declined to about 18,000 by 2001. Although these populations are currently stable, estimates project further declines with loss of habitat (Lindstedt 2005). Most Gulf Coast states have designated this species of “conservation concern” (Bielefeld et al. 2010), largely because of marsh degradation and drainage. Large-scale efforts to restore hydrology of coastal marshes, as well as construction of smaller impoundments, would benefit the species (Moorman et al. 1991; Wilson 2007). Currently, the breeding population in Florida is estimated to be about 40,000 individuals, and the western Gulf Coast population is estimated at 600,000 birds (Johnson 2009), although estimates differ. For example, Delany and Scott (2006) estimated 35,000 individuals in Florida, and only 135,000 individuals in the western Gulf (Alabama to Mexico). The Florida population is stable, while the status of the western Gulf population is unclear. Breeding surveys from National Wildlife Refuges in Texas suggest a precipitous decline since 1985, when the surveys began (Johnson 2009), although breeding bird surveys show a moderate decline, and Christmas Bird counts show a decline in the same period. They increased before the 1990s (see Figure 12.27 below).

The Texas Parks and Wildlife Department (TPWD 2011) conducts annual waterfowl surveys of the central Gulf Coast Prairies and Marshes, and of the southern Coastal Sand Plains. These data indicate trends for one of the important Mottled Duck breeding areas (Figure 12.28). Mottled Ducks were much less abundant in the southern marshes of Texas, compared to the central areas.

Breeding Bird Survey data are useful for Mottled Duck because they only occur along the coasts, and although the number of routes is small, it still provides an index of numbers. Mottled Ducks showed a sharp decline in Texas, and a decline in Louisiana, although they remained stable in Florida (Figure 12.27). Trends in waterfowl populations for Mexico indicated significant long-term declines for some species, but no significant long-term trends for Mottled Duck (Figure 12.27) (Perez-Arteaga and Gaston 2004). They surveyed only two places along the Gulf Coast of Mexico, but this represented 91 % of the Mexican population. The average count last year was 49 % below the mean, and declines since the mid-1980s bear watching (Figure 12.27).

Using Christmas Bird Counts from 1965 to 2011 as a database, Niven and Butcher (2011) reported that Mottled Duck winter populations increased significantly by 1.2 % per year along the U.S. Gulf Coast (Figure 12.28). The conflicting data (Breeding Bird Surveys vs. Christmas Counts) is troubling and bears further examination, especially given the declines at National Wildlife Refuges.

Resiliency is unclear, since the age of first breeding is unknown (perhaps at 1 year); they lay clutches of 8–12 eggs, and breeding success is unknown (Bielefeld et al. 2010). While intrinsic resiliency may be intermediate to high (based on age of breeding and clutch size), massive loss of habitat gives them few options for movement because they are an obligate estuarine species.

These dramatic white-headed, eagle-sized hawks are familiar to coastal people throughout the United States (Figure 12.29). They are the only North American raptor to feed entirely on fish; they have strong, sharp claws and are also called “fish hawks.” Ospreys are one of the most widespread species in the world; they breed or winter on all continents except Antarctica (Farmer et al. 2008). Their main breeding range in North America extends north to central Alaska, northwest Yukon, Northwest Territories, Saskatchewan, Manitoba, and Ontario, to the tree line of Newfoundland (Poole et al. 2002). They dip down into the western, central, and eastern United States, and breed along the Atlantic coast down to almost the tip of Florida, as well as sporadically along the northern Gulf Coast (Eubanks et al. 2006). A nonmigratory race breeds in Cuba (Raffaele et al. 1998). On the west coast they breed down the coast from Alaska to northern California, on Baja California coasts, and on the western Mexican mainland (Poole et al. 2002). The bulk of the North American population winters south of the United States in Central and South America (Poole et al. 2002).

They dive feet first to capture their prey from the top meter of water; this restricts them to surface-schooling fish and to shallow water. Where there is shallow water and abundant prey, they nest more densely and are considered semicolonial (Poole et al. 2002). They frequent large lakes, rivers, and coastal areas where manmade structures provide perches and nesting sites. Most breed at 4 years of age. They are monogamous, lay a clutch of 1–4 eggs in April, only the female incubates (35 days), and they fledge their young in July and August. Fledging success varies greatly from region to region, perhaps as a result of prey availability. Ospreys make long migrations to Central and South America, although some remain in Florida and Mexico, and more recently, in the other northern Gulf States.

Osprey, like many other fish-eating birds, suffered population declines from the 1950s through the 1970s due to pesticides (DDT) and other contaminants (Poole et al. 2002). The chemicals resulted in eggshell thinning, depressed reproduction, and population declines. The percent of eggshell thinning was directly related to levels of dichlorodiphenyldichloroethylene (DDE), a metabolic breakdown product of DDT. Since the ban on DDT, populations have rebounded.

In 1983, there were about 8,000 breeding pairs in the United States (Henny 1983) and 16,000 to 19,000 pairs in 2001 (Poole et al. 2002). The population in the United States and Canada is about half of the world population of approximately 100,000 birds (Farmer et al. 2008). Migration counts and Breeding Bird Surveys indicate that populations have increased or remained stable; east and midwestern North America had greater increases than in the Great Lakes or western North America, based on counts in the Gulf of Mexico (Farmer et al. 2008). Surveys of Osprey at four locations around the Gulf of Mexico from 1995 to 2005 indicated that they increased significantly in the Florida Keys, in South Point and Corpus Christi, Texas, but with no significant trend in Veracruz, Mexico (Smith et al. 2008).

Christmas Bird Count data shows a clear increase in Osprey in the Gulf States, although the greatest increase was in Florida (Figure 12.30). The increase in Florida was rather steady, but increases in the other states began in the early 1980s.

Resiliency in Osprey is low to intermediate; they breed at 4 years of age, and lay an average of three eggs, but most Osprey do not live beyond 12 years. Since they eat fairly large fish, they are vulnerable to effects from mercury, as well as to pesticides and other contaminants. They forage in shallow water and are more affected by fish abundance and behavior than other species that can fish at a greater water depth. While they adapt to the presence of people, they can suffer disturbances from approaching boats.

Whooping Cranes, the tallest North American birds (1.5 m), are snowy white with black primaries, and a brilliant carmine crown (Figure 12.31). They are a symbol of international efforts to save an endangered species, and were brought back from the brink of extinction with collaboration among Canadian and U.S. provincial and state agencies (USFWS 1986; Lewis 1995). In 1941, only 15–16 individuals wintered in Texas. They were placed on the Endangered Species List in 1967 and are one of the rarest birds in North America. Whooping Cranes are omnivorous, feeding on insects, frogs, rodents, small birds, minnows, and berries in the summer, and estuarine animal foods (blue crabs and clams) in the winter (USFWS 2010b). On their wintering grounds, in the area between the Rio Grande and Galveston Bay, Whooping Cranes feed in three habitats: (1) estuarine intertidal unconsolidated shore mud, (2) palustrine emergent persistent wetlands, and (3) estuarine intertidal emergent persistent wetlands (Anderson et al. 1996).

Whooping Cranes were once widespread, although not common in the prairie marshes of north-central United States and southern Canada, and they were a common winter resident along the coast, even in Louisiana (Lowery 1974). They are monogamous, mate for life, and nest in bulrushes (USFWS 2010b). The incubation period is 29–31 days, and chicks fledge in 80–90 days (Lewis 1995). They remain in family groups following fledging, and the young learn the migration route from their parents. On migration they face weather-related problems, shooting, and collisions with wires and fences, and on the wintering grounds they face shooting, disease, and predation (CWS/USFWS 2007; Gil-Weir et al. 2012). They fly some 2,600 mile (over 4,000 km) between their breeding grounds and Texas.

The Whooping Crane population from 1860 to 1870 was estimated at 1,300–1,400 (Allen 1952), although others estimated it at only 500–700 birds (Lewis 1995). In 1937, only two breeding populations remained: a sedentary population in southwestern Louisiana and the Wood Buffalo population that migrated to Aransas National Wildlife Refuge (Lewis 1995). A hurricane in 1940 reduced the Louisiana population from 12 to 6, and the last individual was taken into captivity in 1950.

There is currently only one truly wild population of Whooping Cranes; they breed in Wood Buffalo National Park in Northwest Territories and adjacent Alberta, and winter at Aransas National Wildlife Refuge (Lewis 1995; USFWS 2010b; WCCA 2012). There are, however, other Whooping Cranes at four places: (1) Grays Lake National Wildlife Refuge in Idaho, (2) Kissimmee Prairie in Florida, (3) an eastern migratory population, and (4) captive populations (USFWS 2010b, 2012c; WCCA 2012). In 2012, the total world population of Whooping Cranes was 571, of which 73 % were in the wild; the remainder were in research facilities or zoos (Table 12.8) (WCCA 2012).

The Aransas/Wood Buffalo National Park Whooping Crane population has continued to grow steadily (Figure 12.32). Resiliency in Whooping Crane is low as they start breeding when they are 4 years old, lay only two eggs, and have an estimated life span of 22–24 years (USFWS 2012c, d), although some scientists believe it is as high as 30 (Lewis 1995).

Clapper Rails are large (the size of a half-grown chicken) with gray-cinnamon buff tails and a long decurved bill. They are emblematic of salt marshes and mangrove swamps, although they are more often heard rather than seen as they skulk through the marsh (Figure 12.33). Their breeding range is from the northern United States to Brazil on the coastal fringes. They range from Massachusetts south to the Florida Keys, on the Gulf Coast from Cape Sable (Florida) west to Tamaulipas, Mexico, and from San Francisco to Baja California, as well as in some inland areas (such as the Salton Sea). Their ranges in Mexico, Central America, and South America are poorly known, but they are reported from many areas (Eddleman et al. 1998). Most populations are resident, but the more northerly rails move south in the winter.

Clapper Rails are strictly estuarine—they very infrequently nest in freshwater marshes (Olson 1997), and are thus good indicators of marsh conditions, especially contaminants, oil, and habitat loss (Novak et al. 2011). They are a solitary species, and space out within marshes or mangroves. Clapper Rails mainly feed on crustaceans (Eddleman et al. 1998). They build nests in thick vegetation on the higher places, usually where vegetation is taller, providing some protection from aerial predators. They lay 7–9 eggs; most nest failures are due to predation on eggs, and flooding, which is likely to increase with sea level rise. Although young rails feed on their own, they remain with parents until they fledge.

Future habitat changes that result from environmental stress, sea level rise, and subsidence will result in a landward increase in salinity (McKee et al. 2004), with changes in vegetation types and nesting bird populations (Greenberg et al. 2006). Since Clapper Rails nest and forage in habitats with higher salinity than some salt marsh birds, they may increase in Gulf Coast marshes with increased salt water intrusions (Rush et al. 2009a). While habitat loss is the most critical factor, tidal flooding and hunting pressures also decrease their populations (Stevenson and Anderson 1994). Because Clapper Rails breed and forage in coastal marshes and remain hidden most of the time, it is difficult to track their population numbers, although high tides (Rush et al. 2009b) and recent advances in acoustical monitoring make it easier to count them. There are no estimates for the number of Clapper Rails in Gulf Coast marshes, although they are counted on Breeding Bird Surveys and on Christmas Bird Counts. Breeding Bird Surveys indicate that they are declining in all states, except Louisiana, with lower declines in Florida than elsewhere (Figure 12.33).

Using Christmas Bird Counts from 1965 to 2011 as a database, Niven and Butcher (2011) reported no significant trend in Clapper Rail wintering populations along the U.S. Gulf Coast. However, when these data are examined in detail, there appears to be a decline in the northern Gulf from the mid-1970s to the present (Figure 12.34).

Resiliency may be intermediate to high, depending upon the availability of a source population. If a population is extirpated from a region because of habitat loss or degradation, excess available breeders from nearby areas would be necessary to reestablish the population. They likely breed at 1 year, have average clutch sizes of more than nine eggs in the Gulf Coast, and have variable hatching success, depending upon flood losses, that can average 85 % (Eddleman et al. 1998).

Snowy Plovers are small, snowy shorebirds that blend in with their sandy habitat until they move (Figure 12.35). They were formerly considered conspecific with Kentish Plover (Charadrius alexandrines) in Eurasia, but are now separated as a distinct species (C. nivosus) (Page et al. 2009). Two subspecies of Snowy Plover breed in North America, one that nests west of the Rocky Mountains, and one that breeds east of the Rockies, primarily on the Gulf Coast (Paton 1994; Elliott-Smith et al. 2004). The west coast subspecies is already listed as threatened on the U.S. Endangered Species List, and the southeastern birds are currently being considered for listing (Brown et al. 2001). Both populations of Snowy Plover are listed as declining by the U.S. Shorebird Conservation plan (USSCP 2004). Snowy Plover has been given the highest conservation priority by the Gulf Coast Prairie Working Group (GCPWG 2000). Recently, Thomas et al. (2012) estimated the total breeding population of Snowy Plovers in North America as 23,555 (95 % confidence limits = 17,999–29,859), and noted that they may be one of the rarest of shorebirds in North America.

In the Gulf Coast, Snowy Plover are distributed sparsely along the southwest coast of Florida north to Anclote Key and along the Panhandle, in Alabama and Mississippi (mainly on offshore islands), in Louisiana—only two pair in 2001 (Zdravkovic 2005), along the lower Texas coast from Matagorda Island to the Mexican border, and south to Veracruz and the northern coast of the Yucatán Peninsula (Page et al. 2009), where they have been observed in flocks of 100 (Ornat et al. 1989). Results from a recent survey of breeding Snowy Plovers in North America, conducted in 2007 and 2008, indicated that 42 % of all breeding Plovers resided in Great Salt Lake in Utah and Salt Plains National Wildlife Refuge in Oklahoma (Thomas et al. 2012). The total population for the coast of the Gulf of Mexico was 4,515 (19 % of total). Approximately 9 % of the North American breeding population occurs in Mexico (Thomas et al. 2012).

Snowy Plover are attracted to extensive beaches with tidal pools and sand flats that provide foraging areas, although they will also feed in marshes (Withers 2002). They eat small mollusks, crustaceans, marine worms, and insects. In winter, Snowy Plovers often associate with Piping Plovers (Elliott-Smith et al. 2009) and Wilson’s Plovers (Charadrius wilsonia) (Howell and Webb 1995). Snowy Plovers nest on sandy beaches on the mainland and on barrier islands, where they make nest cups on the sand, sometimes in colonies with Least Terns (Stevenson and Anderson 1994). Incubation period is 28 days (Warriner et al. 1986); both sexes incubate, and females desert the brood soon after hatching (Page et al. 2009). Counting Snowy Plovers during the breeding season is difficult because studies of marked individuals indicate that at least twice as many birds are present for each one seen, and detection probability is 0.58 (Warriner et al. 1986; Hood and Dinsmore 2007).

Populations of Snowy Plover are likely lower in the Gulf Coast than they were in the late 1880s due to habitat loss and disturbance (Page et al. 2009). Hood and Dinsmore (2007) identified the Laguna Madre (Texas) as an important breeding area, suggesting that it be protected from development since the species is reported to be declining in the Gulf. Coordination with Tamaulipas, Mexico is critical for protection of this species; wintering Snowy Plovers use the algal mudflats there, illustrating the importance of the entire Laguna ecosystems (Mabee et al. 2001). Morrison et al. (2006) reported that the Gulf of Mexico and Caribbean race of Snowy Plover is decreasing, and likely was only 1,500 birds, although more were counted on the next census (Table 12.9) (Elliott-Smith et al. 2009).

Computing 3-year averages using Christmas Bird Count data from 1942 to 2010 indicates variability in the numbers of Snowy Plovers counted (Figure 12.35). Although there appears to be an overall increase, they have declined since 1995 (Niven and Butcher 2011). It is hard to interpret the two peaks in the early 1950s and early 1960s.

Resiliency in Snowy Plover is intermediate as they breed when 1 year old, lay a mean clutch of three eggs, and hatching success varies greatly from 12.5% to 87 % (often depending on the degree of human protection), but they can have multiple broods per season (Page et al. 2009). Paton (1994) estimated a mean adult survival of 2.7 years. Vulnerability of nests and chicks, habitat losses, human disturbance, and mammalian predators all contribute to lowered success, particularly in the Gulf.

Piping Plovers are a threatened and endangered shorebird that lives on open beaches, alkali flats, and sand flats. They have a distinctive dark and white pattern of bands on the head, neck, and upper breast (Figure 12.36). The black and white breaks up the outline of birds, allowing them to disappear when motionless. They were listed in 1985, and recovery plans for several regions have been developed (USFWS 1999). They are endemic to North America, with a total population of about 8,000 (Gratto-Trevor and Abbott 2011). The Piping Plover has been given the highest conservation priority by the U.S. Shorebird Conservation Plan, including for the Gulf Coast where they only winter (GCPWG 2000).

They breed on the Atlantic coast of Canada and the U.S. Great Lakes region, Great Plains, the Canadian Prairies, and St. Pierre and Miquelon (French territories off the southwest coast of Newfoundland) (USFWS 1999; Elliott-Smith et al. 2004). They do not breed in the Gulf of Mexico. They winter along the Atlantic and Gulf coasts (into Mexico), and in the Caribbean (Elliott-Smith et al. 2004; Gratto-Trevor and Abbott 2011). Piping Plovers in Texas show wintering site fidelity (Drake et al. 2001).

Piping Plovers forage on beaches, washover areas, and tidal flats on small invertebrates (Withers 2002). They frequently nest on sandy beaches with little vegetation, but with some shell or pebble cover; often near dunes (Wilcox 1959; Burger 1987b; Maslo et al. 2011). They are monogamous for one breeding season, although there are rare reports of sequential polyandry (Amirault et al. 2004). Both members of the pair incubate their four-egg clutch for 26–31 days (USFWS 1999), and both parents brood the young (Gratto-Trevor et al. 2010). The parents draw predators from their nests and chicks with very elaborate distraction displays, which involve a broken wing act (Figure 12.36).

They are dependent on management, such as restrictive access for off-road vehicles (Burger 1991b, 1994b; USFWS 1999; Maslo and Lockwood 2009). There is controversy about the effectiveness of nest protection techniques. Nest protection includes nest enclosures (predator exclosures), electrified wires on enclosures, fencing (mainly for people), wardening, predator control, and captive breeding (Burger 1987b; Murphy et al. 2003; White and McMaster 2005; Cohen et al. 2008, 2009; Maslo and Lockwood 2009). Beach nourishment increases habitat for Piping Plover (Webster 2006). Management has largely focused on reducing mortality during the breeding cycle, and it is unclear whether the sustained efforts required can be maintained (Gratto-Trevor and Abbott 2011).

As a federally endangered species, Piping Plovers are useful indicators because their populations are closely monitored, and their wintering in the Gulf Coast makes them vulnerable to coastal stressors. Populations declined during shorebird harvesting for the millinery trade in the late 1880s and early 1900s (USFWS 1999). In the latter half of the twentieth century, however, Piping Plover populations declined because of habitat loss and alterations, human disturbance, and increased nest predation (Sidle 1984). The breeding population estimate of 5,945 plovers is probably an underestimate (Elliott-Smith et al. 2009). The U.S. Fish and Wildlife Service identified human disturbance and habitat loss as the two greatest threats to Piping Plovers on the wintering ground (USFWS 2009b). Other threats during the fall and winter include hurricanes, oil spills, and red tides. Gratto-Trevor and Abbott (2011) provide the best and most comprehensive review of conservation efforts for Piping Plover.

A complete winter survey of Piping Plovers was conducted in 1991, 1996, 2001, and 2006 (Haig and Plissner 1993; Haig et al. 2005; Elliott-Smith et al. 2009). In 2001, they reported 2,389 piping plover during the winter, but 5,945 adults were counted during the breeding season (Haig et al. 2005). In 2006, the International Piping Plover Census covered more than 12,400 km of potential habitat in 2 weeks (2,470 sites, 1,300 observers) (Elliott-Smith et al. 2009; Gratto-Trevor and Abbott 2011). More Piping Plovers were recorded in 2006 in the northern Gulf than in either 1996 or 2001, but numbers were lower than in 1991. In all years, Texas had most of the Piping Plovers (Table 12.10).

It is also instructive to examine the Christmas Bird Count data for yearly variations (Figure 12.37). Despite recovery efforts, the number of wintering Piping Plovers counted along the Gulf Coast has remained relatively constant, and appears to have declined since the late 1990s.

Resiliency of Piping Plovers is apparently relatively low, as indicated by the great effort by the USFWS Recovery Team and state agencies to protect nesting and foraging habitats, with relatively modest success (USFWS 2003, 2009b). They breed the first spring after hatching, the number of chicks fledged per year varies from 0.3 to 2.5 per nest, and average life span is 5 years (Wilcox 1959; USFWS 1999; Elliott-Smith and Haig 2004; Gratto-Trevor et al. 2010). However, since they nest on sandy beaches exposed to human disturbance, predators, high nest failures, and habitat loss, resiliency of breeding populations is low, explaining the recent decreases in wintering birds along the Gulf of Mexico.

Laughing Gulls are small, dainty, black-hooded gulls that careen low over beaches and mudflats, or soar high in the air hawking insects (Figure 12.38). They nest in colonies of up to 25,000 pairs on sandy or rocky shores, and in salt marshes along the Atlantic and Gulf coasts of North America, as well as on some Caribbean islands, the Gulf of California, and Pacific coast of Mexico (Burger 1996a). Although they nest on the Chandeleur Islands of Louisiana, they do not nest in Mississippi (Turcotte and Watts 1999). They also nest on the islands in the Campeche Bank of the southern Gulf (Tunnell and Chapman 2000). They winter from North Carolina south through the remainder of the breeding range, along the west coast of Baja California, and along the Pacific coast from Colima, Mexico, south to Peru, the Galapagos, and Chile (Burger 1996a). They are particularly common in winter in the southern Gulf of Mexico (Howell and Webb 1995). Formerly Larus atricilla, Laughing Gulls are now listed as Leucophaeus atricilla in the latest AOU checklist and supplements (AOU 1998).

Laughing Gull populations were devastated by market hunting for plumes and eggs in the late 1880s and early 1900s (Sprunt 1954). They expanded their numbers thereafter in the northeast, but suffered competition with the larger Herring Gulls that did not breed in the region until the late 1940s (Burger 1983). Laughing Gulls did not face such competition from an expanding exotic species in the Gulf of Mexico, perhaps accounting for their large populations there. They are good indicators because they are common along the Gulf Coast, are nesting and foraging generalists, and are an integral component of nesting colonies and foraging assemblages both along the coast and in the Gulf.

Laughing Gulls are generalist foragers, eating fish, insects, other invertebrates, and garbage. They follow shrimp boats in Texas (Eubanks et al. 2006) and fishing boats off Mississippi (Turcotte and Watts 1999) in search of scraps. They dive for fish, follow boats that stir up prey, “hawk” for flying insects, and catch food thrown by beach-goers or fishermen (Stevenson and Anderson 1994; Burger and Gochfeld 1983c).

Laughing Gulls are one of the most common breeding birds along the Gulf Coast, and they are residents, migrants, and winter visitors. They do not nest in Alabama (Imhof 1962), but they do on the nearby Chandeleur Islands of Louisiana (Imhof 1962), where they are mainly coastal and rarely move inland (Lowery 1974). Along the Gulf they nest on sand and in marshes (Imhof 1962; Schreiber and Schreiber 1979; Burger 1996a, b). Most Laughing Gull colonies in coastal Louisiana are in marshes (80 %), and the remaining 20 % are on sand or in shrubs (Greer et al. 1988). They are monogamous, lay three eggs, and both sexes incubate and care for the young (Burger 1996a). Yearly differences in reproductive success are due to flooding, predators, and human disturbance (Burger 1996a). Nesting is a compromise between nesting on islands that are high enough to avoid flooding, while being low enough to avoid mammalian predators, and competition with other ground-nesting colonial species (Burger 1983).

A significant proportion of the North American breeding population is located in the Gulf. Many Laughing Gulls that breed along the Gulf Coast remain there, wandering along the coast in the winter, while gulls from farther north also winter along the Gulf Coast. Local surveys provide an indication of trends information. For example, periodic surveys in Galveston Bay indicate that Laughing Gulls make up a significant portion of the colonial nesting birds (Table 12.11) (Glass and Roach 1997). From 1973 to 1996 nesting pairs of Laughing Gulls declined. In 2001, there were 22,000 breeding pairs in the Galveston Bay survey (Eubanks et al. 2006). The downward trend has continued; the Galveston Bay Status and Trends Project rated Laughing Gulls as significantly decreasing (GBEP 2006).

Similarly, information from Louisiana shows declines in the number of breeding Laughing Gulls (Figure 12.39) (Visser and Peterson 1994).

There was an overall increase in Laughing Gulls on Shamrock Island in Texas from 1973 to 1999 (Figure 12.40). The trend continued until about 2007 and then declined (TCWS 2012). Information from Tampa Bay shows that the number of breeding pairs was stable until about 2008, and then they increased (Hodgson and Paul 2010). Data from Breeding Bird Surveys show a different pattern, with Laughing Gulls increasing in Texas and Alabama (Figure 12.41). This bears further examination and suggests that population trends need to be followed for a region, rather than for one colony. Furthermore, the counts are from shore and not from boats near breeding islands, which may suggest that Laughing Gulls are now foraging closer to shore.

Using Christmas Bird Counts from 1965 to 2011 as a database, Niven and Butcher (2011) reported that wintering Laughing Gulls showed a significant increase of 3.0 % per year in the Gulf region. This may reflect an increase in wintering Laughing Gulls, rather than from local residents. Using Christmas Bird Count data from 1940 to 2005, 3-year running averages were computed, showing a decline from the 1990s to the present (Figure 12.41). The 1-year increase (mainly Texas) in the last year may not reflect a real increase. These two conflicting analyses indicate the difficulty of taking different time periods to examine trends. It appears that the 40-year trend may be increasing, but the trends over the last 15 years are decreasing for both breeding populations and wintering populations along the Gulf.

Resiliency in Laughing Gulls is intermediate to high because they can breed when 3 years old, lay three eggs, have high hatching success (74–81 % in Florida) (Schreiber et al. 1979), fledge up to 1.32 chicks per nest, and live up to 19 years (Burger 1996a). Recovery potential is high, but in the Gulf this must be balanced against losses due to habitat loss, predators, tidal flooding, and hurricanes (Burger 1978b).

Royal Terns are large, stocky terns with bright orange bills and a black crest when they start breeding. They breed primarily along the Atlantic coast from Virginia south to Florida, and along the Gulf Coast to Texas, throughout the Caribbean, along the Pacific coast of Mexico, and on the Atlantic coast of South America (Buckley and Buckley 2002). They are common breeding birds along the Gulf, nest on islands off Veracruz (Howell and Webb 1995), in the Campeche Banks (Tunnell and Chapman 2000), and in the West Indies, northern South America, and on islands in the Caribbean (Buckley and Buckley 2002). They are rarely found inland (Sprunt 1954). Formerly Sterna maximus, they are now listed as Thalasseus maximus in the latest AOU supplements (Figure 12.42).

Royal Terns are of interest because they nest on the sand in large colonies, have high colony turnover rates, and the Royal Terns along the Gulf represent about 40 % of the U.S. breeding population (Visser and Peterson 1994; Lindstedt 2005). Abandonment of colonies is indicative of habitat quality problems that need to be addressed in the Gulf States. Royal Terns forage on small prey fish, which they capture by diving, but they also eat squid, shrimp, and crabs in Florida (Stevenson and Anderson 1994).

Royal Terns nest in dense groups, either in monospecific colonies, or with other terns (e.g., Caspian, Sandwich), Laughing Gulls, and Black Skimmers (Figure 12.43). Royal Terns nest a mere body length apart. When they nest with other species, they still nest in dense groups, which may be within or adjacent to more spaced-out gulls and terns. Royal Terns lay one egg, both incubate, and both provision the young. There is usually synchrony in egg-laying within subcolonies, which results in synchronous hatching. Parents brood very young chicks, but chicks quickly join a crèche (young birds that stay in a close-knit group), which protects them when parents are away foraging (Buckley and Buckley 2002). Buckley and Buckley (2002) estimated the number of breeding pairs for the Gulf region as follows: 1,000 in Florida (both coasts), 250 in Mississippi, 10,590 in Louisiana, and 22,463 in Texas. Breeding populations in Louisiana declined in the early 1990s (Figure 12.39) (Visser and Peterson 1994). They attributed the variability in nesting numbers to the vulnerability of their nesting habitat to storms and high tides. Delany and Scott (2006) estimated the number of Royal Terns in the United States to be 139,000. Trends data from Shamrock Island in Texas (Figure 12.40) indicates an overall increase in the number of breeding Royal Terns until the mid-1990s (Gorman and Smith 2001), and then they declined (TCWS 2012). Breeding Bird Survey data indicate a great increase in Royal Terns in Louisiana, but a slight decline in Alabama and Texas (Figure 12.44).

Analysis of Christmas Bird Count data does not indicate a significant trend (Niven and Butcher 2011), although an examination of data from Florida seems to indicate a decline, as well as a decline in the Gulf Coast overall (Figure 12.45).

Resiliency is intermediate because they do not breed until the age of 5–6 years and lay one egg, and Royal Terns can live up to 28 years, but most live fewer years (Buckley and Buckley 2002). There are few data on reproductive success because the young form crèches, making it difficult to follow families. Royal Terns have extended parental care up to the second year (Buckley and Buckley 1974), placing an additional stress on parents.

Black Skimmers, which are about the size of a Royal Tern, are familiar and striking as they fly silently just above the water with their bill dipped in—skimming (Figure 12.46). They breed from Massachusetts south along the Atlantic and Gulf coasts to southern Mexico, on islands in the Caribbean, and from southern California (and inland Salton Sea) to Nayarit, Mexico (Gochfeld and Burger 1994). A significant proportion of the world population of Black Skimmers breeds along the Gulf Coast. They winter from North Carolina south, along the Gulf Coast, south to Panama, and on the Pacific Coast to Costa Rica (Gochfeld and Burger 1994). Birds breeding in Florida are residents (Stevenson and Anderson 1994), which may also be the case for the rest of the Gulf Coast. One estimate for the number of Black Skimmers nesting along the Atlantic and Gulf coasts is 90,000 to 101,000 individuals; another 4,200 are in California and on the Pacific coast of Mexico (Delany and Scott 2006).

Black Skimmers skim across the water’s surface to catch fish and invertebrates, feeding within the top 5–6 cm of water, often at dusk or at night (Erwin 1990; Burger and Gochfeld 1990; Yancey and Forys 2010). At St. Vincent National Wildlife Refuge on the Gulf Coast of Florida, 71 % of Black Skimmer foraging occurred within 2 m of the land (in water depths of 13.4 cm, Black and Harris 1983).

Black Skimmers usually nest on bare sand in colonies with gulls and terns, including Least, Sandwich, Royal and Caspian Terns, and Laughing Gulls, deriving some protection from their aggressive neighbors (Gochfeld 1978; Erwin 1979; Burger and Gochfeld 1990; Turcotte and Watts 1999). They also nest on dredge spoil or on salt marshes (Figure 12.47), and in northwestern Florida, on roofs (Gore 1991). In coastal Louisiana, Skimmers nest mainly in herbaceous vegetation (79 %), or on sand and shell beach (12 %, N = 27 colonies) (Greer et al. 1988). Black Skimmers are monogamous; courtship is synchronous; they lay up to six eggs, and both sexes incubate, defend the nest, and care for the chicks (Gochfeld 1980; Burger 1981e; Burger and Gochfeld 1990, 1992). The chicks are cryptically colored and blend in with sand or bleached wrack, and remain motionless until a predator or person is upon them, when they run frantically for cover (Burger and Gochfeld 1990; Gochfeld and Burger 1994). Skimmers often fail to brood chicks during heavy rains, and lose more chicks to cold stress than do terns (Burger and Gochfeld 1990).

Black Skimmer populations declined from oil and organochlorine chemicals in the 1960s and 1970s (Gochfeld 1973, 1974, 1979; Custer and Mitchell 1987). Contaminant levels in the Gulf, however, declined by the early 1980s to below effect levels in Galveston Bay (King and Krynitsky 1986). On the other hand, creation of dredge spoil islands has provided new nesting habitat for Black Skimmers—in Louisiana the numbers of nesting Black Skimmers steadily increased over the 5 years of a study examining the effect of dredge spoil on nesting (Leberg et al. 1995).

Waterbird surveys in Galveston Bay provide some trends information (Glass and Roach 1997). During this time Black Skimmer numbers remained relatively constant, although Laughing Gulls declined (Table 12.11). Trends information from Shamrock Island, Texas indicates an overall decline in the number of pairs on the island from 1973 to 1999, although the numbers did vary (Gorman and Smith 2001). The overall trend after 2000 for Black Skimmers, however, was downward (TCWS 2012), and there is interest in listing the species in Texas (D. Newstead, Coastal Bend Bays & Estuarine Program, Corpus Christi, TX, personal communication). Similarly, the number of breeding Black Skimmers declined in colonies in Louisiana from 1976 to the 1990s (Figure 12.39) (Visser and Peterson 1994). They attributed the decline to erosion of preferred nesting areas, human disturbance, and a reduction in the number of available sites, a recurrent theme for ground nesting colonial birds along the Gulf Coast.

Information from Florida also indicates statewide declines in the number of breeding Black Skimmers (Figure 12.47) (Hodgson and Paul 2010; FFWCC 2011b). Stevenson and Anderson (1994) refer to a single colony of 2,000 pairs in 1935, which is very large by current standards. By the late 1970s, the largest colony in the state was 1,000 pairs in Nassau County (Clapp et al. 1983). During the 2010 nesting season, the largest colony had only 450 pairs, and of the 19 colonies, 12 had fewer than 50 pairs each (FFWCC 2011b).

Breeding Bird Surveys show a steep decline in Alabama, Louisiana, and Florida, with Texas showing a slight increase (Figure 12.48). While there are few routes along the coast, the index provides information, which corroborates the breeding data reported from individual colonies. Using Christmas Bird Counts from 1965 to 2011 as a database, Niven and Butcher (2011) reported that wintering Black Skimmers showed a significant decline of 2.2 % per year along the northern Gulf. Three-year running averages show similar trends (Figure 12.48).

Resiliency in Black Skimmers is intermediate as they delay breeding until they are 3 or 4 years old, lay an average of three eggs, and probably live an average of 10–15 years (Burger and Gochfeld 1994). Since they nest on ephemeral habitats (sandy beaches) or those exposed to flood tides (marshes), reproductive success is often very low.

Seaside Sparrows are small, fairly nondescript brown birds that skulk in grassy vegetation, often running through the grasses (Figure 12.49). They are habitat specialists of salt and brackish marshes and occur in small, localized populations along the Atlantic and Gulf coasts (Post et al. 2009). At least five subspecies breed along the Gulf Coast: Ammodramus maritimus mirabilis (southern tip of Florida), A. m. peninsulae (northern Florida Gulf Coast), A. m. juncicota (Alabama), A. m. fisheri (Louisiana Seaside Sparrow, to Texas), and A. m. sennetti (southern Texas coast) (Post et al. 1983, 2009). Subspecies are separated by expanses of open water and unsuitable habitat. Seaside Sparrows breeding along the Gulf area residents, while those nesting in the northeastern United States migrate to the southern Atlantic and do not migrate to the Gulf. Distribution of breeding Seaside Sparrows is not uniform, leading to the suggestion that they are semicolonial (Post et al. 2009).

Seaside Sparrows forage on grasshoppers, crickets, caterpillars, flies, moths, spiders, snails, mollusks, and small crabs, such as Fiddler Crabs, and grass seeds (Imhof 1962). They nest solitarily, occurring in relatively small, localized populations (Post et al. 2009). Although they sometimes occur with Sharp-tailed Sparrows (Ammodramus acuticauda), in some places, such as Alabama, they nest in wetter places than the latter species (Imhof 1962). In resident populations, such as those in the Gulf, females may remain all year on the male’s territory, retaining the same mate from year to year (Post et al. 2009). Females lay 4–6 eggs, and the female incubates alone. Eggs and chicks are vulnerable to predation and tidal flooding (Post et al. 2009).

Seaside Sparrows are good indicators of the presence of healthy expanses of salt marsh; Louisiana Seaside Sparrows reside exclusively in brackish and saline marshes along the northern Gulf and are representative of the threats faced by species that breed and winter in these marshes. They are considered a species of management concern throughout their range because of habitat loss and alteration and human disturbance (Cowan et al. 1988; Greenlaw 1992). Responses to burning are unclear because the effects relate to timing (Gabrey and Afton 2000). Sparrows evolved with lightening-induced natural fires that create mosaic patterns, leaving some places unburned. In contrast, anthropogenic burning often involves large, continuous patches. Gabrey and Afton (2000) concluded that management should maintain a mosaic of burned and unburned marsh to provide adequate refuges for sparrows.

Breeding Bird Survey data for Seaside Sparrows indicate increases in Texas and Louisiana, but it is unclear how reliable these data are, given the difficulty of locating this species (Figure 12.50). Christmas Count data for the U.S. Gulf States indicates declines (Figure 12.50).

Resiliency is intermediate to high because they start breeding the spring after their hatching year, lay 2–5 eggs (modal of three in the south), and have a potential life span of 8–9 years (Post et al. 2009). Little life history information is available for A. m. fisheri, the species that occurs from Louisiana to southern Texas. Recovery is likely low, given the loss of marshland and tidal/storm flooding while nesting.

It is also useful to compare indicators. Two examples illustrate variations among species: Breeding Bird Surveys for the Gulf of Mexico and habitat use by water birds at Laguna Madre in Texas (Anderson et al. 1996). These were chosen because they include many different species of birds.

The Breeding Bird Surveys, conducted by the U.S. Bird Banding Laboratory, provide useful data on trends (Figure 12.51). The Banding Laboratory produces maps that indicate whether populations are increasing or decreasing.³ The data provide trends information that corroborates, for the most part, individual studies conducted in states and regions. A glance at Figure 12.51 shows that Osprey and Royal Tern are increasing in the U.S. Gulf, while Mottled Duck and Clapper Rail are declining in several states. There are some shifts, where populations appear to be declining in some parts of the Gulf, and increasing elsewhere, including Brown Pelican and Black Skimmer. Furthermore, there are no data for Reddish Egret and Seaside Sparrow, both species of concern for the Gulf. However, these are long-term trends, and the trend over the last 10–15 years may differ, as is clear from the temporal patterns provided in the indicator accounts. The indicator accounts show that Black Skimmer is declining and that Laughing Gull has declined over the last 20 years.

Laguna Madre (in Texas) is the second example. More than four million birds (100 species) use the Laguna Madre in mid-winter, including 35 species of shorebirds, 20 species of wading birds, and waterfowl (Muehl et al. 1994; ABC 2011). Anderson et al. (1996) examined bird use of 82 different wetland types between the Rio Grande and Galveston Bay, and found clear differences in both the diversity and types of habitats used. Some groups used many different habitat types (Gallinule and Coots), while others such as rails and grebes used few habitat types (Table 12.12). Differences among species, however, are of interest; Table 12.12 lists habitat uses of the indicator species (calculated from data in Anderson et al. 1996). There were interspecific differences in the number of habitats used, even within a group of closely related species. For example, Spoonbills used only 16 habitats, while Snowy Egret used 52. They drew the following conclusions: (1) cormorants and pelicans used wetlands with less than 30 % vegetation; (2) gulls, terns, and skimmers used estuarine and lacustrine wetlands with less than 30 % vegetation; (3) grebes and rails used palustrine aquatic-bed rooted vascular wetland types; (4) herons, egrets, and bitterns used lacustrine and estuarine wetlands; and (5) shorebirds used estuarine intertidal wetlands.

Much of the focus in this chapter and by state and federal agencies, scientists and others, deals with birds that concentrate along the coasts. It is far easier to census birds nesting there than it is to study pelagic seabirds. However, many seabirds mainly use the open, pelagic zones of the Gulf of Mexico. Seabirds do not simply migrate over or around the Gulf, but instead use the open waters of the Gulf for wintering and foraging. The Gulf waters also provide foraging habitat for more tropical-nesting species, some of which use the Campeche Banks for breeding (Tunnell and Chapman 2000), such as frigatebirds and boobies, and for North Atlantic-nesting species, such as Northern Gannet (see section below).

Of all the birds considered, the distribution and behavior of pelagic species are the most affected by prey availability and oceanic features (Hunt 1990; Schneider 1991; Ribic et al. 1997; Schreiber and Burger 2001a, b; Zuria and Mellink 2005). In the Gulf of Mexico, the Loop Current and eddy systems greatly affect distribution of seabirds in the northern region (Ribic et al. 1997). Prey is not evenly distributed over the open ocean; individual prey patches are often small and interspersed (Hunt and Schneider 1987). Foraging seabirds can search for prey by (1) looking for the presence of feeding birds (plunge-diving) as a signal of prey availability (Simmons 1972; Gotmark et al. 1986; Gochfeld and Burger 1982), (2) looking for other seabirds flying in the same direction, presumably toward a prey patch, (3) watching birds that return to a colony with food (Gaston and Nettleship 1981), (4) searching for particular oceanographic conditions, and (5) returning to known foraging areas.

Whether or not to associate with marine mammals is another decision foraging seabirds make (Burger 1988b, c). Foraging with mammals (whales, dolphins) can make prey fish more available and identify large expanses of zooplankton; it can also result in competition or interference foraging (Pierotti 1988a). Marine birds and mammals can interact in at least five ways: (1) birds can have passive associations; (2) birds can be attracted to the same resource; (3) birds can be actively drawn to marine mammals because they drive prey to the surface; (4) birds can be attracted to marine mammals to scavenge on by-products of mammal foraging; and (5) birds can actively avoid marine mammals that might prey on them; for example, Orcas eat diving birds (Pierotti 1988b).

Seabirds often forage over schools of prey fish that have been forced to the surface by predatory fish, such as bluefish (Pomatomus saltatrix) or tuna (Safina and Burger 1985, 1988; Au and Pitman 1988). Such schools are usually ephemeral as prey fish soon scatter and swim away from the surface; usually there is no direct competition among the seabirds foraging above them (Burger 1988b, c).

Interactions between seabirds and fisheries include foraging near boats on fish in nets, foraging behind boats on prey churned up by fishing operations, foraging on discarded offal from factory ships, and feeding on offal near onshore facilities (Furness et al. 1992). Some seabirds panhandle food around docks. Many of the interactions among birds, marine mammals, predatory fish, and fisheries operations are described fully in chapters in Burger (1988c; 2017) and in Schreiber and Burger (2001a).

Interactions with fisheries are an ongoing concern for many diving seabirds (Forsell 1999; Gilman 2001; Gilman et al. 2005). The National Marine Fisheries Service Pelagic Observer Program observed 6,949 longline sets from 1992 to 2005 in the U.S. Atlantic longline fishery, which included the Gulf of Mexico (Hata 2006). In 52 sets, 114 seabirds were captured (69 % were dead upon retrieval). Gulls were the most common birds caught, followed by unidentified seabirds, shearwaters, and gannets (Hata 2006). Hata (2006) concluded that seabird mortality was less in Gulf waters than elsewhere.

The U.S. Gulf Coast is not noted for migrant hawks. However, central Veracruz is the most important migratory pathway in the world for hawks (Ruelas et al. 2000; Zalles and Bildstein 2000), and some of these hawks migrate across the Gulf, while others follow the eastern Mexican coast down through Veracruz (Inzunza et al. 2010). As with many other migrants, hawk migration is partly dependent upon wind speed, wind direction, and the passage of cold fronts (Woltmann and Cimpreich 2003). Average counts (±standard deviation) from 1992 to 2004 at Veracruz were as follows (Inzunza et al. 2010): Turkey Vulture (1,897,679 ± 387,839), Mississippi Kite (157,199 ± 87,640), Broad-winged Hawk (1,932,255 ± 287,822), and Swainson’s Hawk (819,419 ± 280,788).

Raptor populations surveyed from 1995 to 2005 at four locations (Florida Keys, Smith Point and Corpus Christi in Texas, Veracruz in Mexico) showed significant declines in some species and significant increases in others (Smith et al. 2008). Species that increased significantly at one or more sites included Turkey Vulture (Cathartes aura), Osprey, Swallow-tailed Kite (Elanoides forficatus), Mississippi Kite (Ictinia mississippiensis), Swainson’s Hawk (Buteo swainsoni), Zone-tailed Hawk (Buteo albonotatus), and Peregrine Falcon (Falco peregrinus). Northern Harriers (Circus cyaneus) and Sharp-shinned Hawks (Accipiter striatus) declined at all sites (Table 12.14) (Smith et al. 2008).

It is often difficult to ascertain population trends for migrating species because shifts in migration patterns may not be readily evident without data from large geographical areas. For example, Farmer et al. (2008) reported declines of North American Kestrel, and long-term increases of Bald Eagle, Merlins, and Peregrine Falcons. However, they attributed the declines to changes in migration patterns (Farmer et al. 2008). Some species, such as Swallow-tailed Kites, are not monitored at hawk watches in North America, making counts along the Gulf Coast particularly important (Smith et al. 2008). Swallow-tailed Kites breed in scattered locations in South Carolina, coastal Mississippi, Alabama and Louisiana, and southern Mexico into South America (Meyer 1995).

The south Texas and Tamaulipas coast are wintering areas for Peregrine Falcons (Enderson 1965; McGrady et al. 2002). The Padre Island Peregrine Falcon Survey, conducted since 1977, provides trends information (Figure 12.54). Because counting migrating hawks is dependent upon observation time, data are given as number of falcon sightings per 10 h time periods. Numbers have varied, but appear to have increased.

One quarter of dabbling ducks once wintered in Louisiana (Palmisano 1973), and two-thirds of the Central Flyway waterfowl population also did so (Bellrose 1988). However, the Gulf Coast is no longer the chief wintering area for North American waterfowl because of coastal marsh habitat loss, sea level rise, and freshwater inputs that have reduced available habitat (Palmisano 1973; Link et al. 2011). Such steep declines require intensive study, management of hunting and habitat, and possible additional protection for nocturnal roost sites (Link et al. 2011), as well as manipulation of water levels (Bolduc and Afton 2004). Even so, 19 % of waterfowl wintering in the United States use marshes of the Louisiana Gulf Coast (Michot 1996). Migratory waterfowl also concentrate in coastal Mexico (Gallardo et al. 2004).

Texas is the top waterfowl harvest state in the Central Flyway and is in the top five hunting states in the United States Texas accounted for 42 % of the total duck harvest and 47 % of the goose harvest in the Central Flyway (TPWD 2011). Although the number of waterfowl hunters is declining nationally, Texas hunter trends have remained stable. Coastal habitat protection is a prime concern of both the Texas Parks and Wildlife Department and the Gulf Coast Joint Venture (GCJV), a regional partnership of organizations and individuals that are concerned with waterfowl and other migratory bird populations and their habitats between Mobile Bay in Alabama and the Rio Grande in Texas (TPWD 2011). More than 1.9 million ducks winter along the Gulf Coast of Texas.

Status and trends data are available for the Texas Gulf from 1997 to 2011 (TPWD 2011). Populations of geese declined during this period (Figure 12.55). In 1997 and 1998 more than two million geese were counted, and by 2001 the numbers had declined to less than a million along the Texas coast (Figure 12.55). This area supported over 552,000 geese annually from 2001 to 2009 (TPWD 2011). Canada Geese numbers declined from over 30,000 to fewer than 7,000 in the last 3 years.

The TPWD (2011) data provide an overview of the relative numbers of ducks (Figure 12.56) as well as trends. Texas Gulf Coast prairies and marshes (mid-Texas coast) have many more ducks than the southern Coastal Sand Plains; yearly average of 1,500,000 compared to the 15-year average of 82,913 (TPWD 2011). Pintail and Gadwall were the two most common dabbling ducks in both regions, while other species, such as shovelers, were less common. Redhead and Scaup were the most common diving duck in the Prairies and Marsh region; only Scaup was most common along the southern coast. The Texas Gulf Coast also provides year-round habitat for Mottled Ducks, Black-bellied Whistling Ducks, Fulvous Whistling Ducks, and to a lesser extent, Blue-winged Teal (TPWD 2011).

The number of dabbling and diving ducks varied by year, and there appears to be a decline in the last 3 years for both groups (Figure 12.57). Although there was a decline from 1999 to 2001 for dabbling ducks, it was not as great, and no similar decline was found for diving ducks. The recent declines may be due to habitat loss caused by severe hurricanes and storms; hurricanes of 2004 and 2008 adversely affected available habitat for wintering waterfowl along the Texas and Louisiana coasts (TPWD 2011).

Wintering waterfowl populations have declined precipitously in the Mobile Tensaw Delta in Alabama (Figure 12.58). Surveys conducted by Lueth (1963) showed a significant decline in populations from 1939 to 1949, and data from the Alabama Wildlife and Freshwater Fisheries Department (AWFWF 2005) show these declines have continued to 2004. These data form a picture of severe waterfowl population declines in the Mobile-Tensaw Delta (Lueth 1963; Beshears 1979; Goecker et al. 2006; MBNEP 2008).

Nesting colonial waterbirds, an important component of the avifauna of the Gulf Coast, nest in abundance on the marsh islands, sandy beaches, and islands with low shrubs in coastal environments. A large number of colonial nesting birds occur throughout the Gulf, including 14 species of herons, egrets, ibises, spoonbills, and storks, as well as ten species of gulls, terns, and a skimmer (Table 12.4) (Gallardo et al. 2009). The northern Gulf Coast alone contains a substantial percentage of the U.S. breeding populations of a number of species, such as Reddish Egret, Sandwich Terns, and Black Skimmers, as well as significant portions of U.S. breeding gulls and other terns (Visser and Peterson 1994).

Nesting colonial birds have long been considered indicators of ecosystem health (Furness 1993; Burger 1993, 2006a, b; Erwin and Custer 2000; Burger and Gochfeld 2004b). Some colonial birds (White Ibis) are noted for their yearly shifts in colony sites and population numbers, although others use the same site for decades or longer (Frederick and Spalding 1994; Schreiber and Burger 2001a). Thus, regional estimates are most useful for species that shift sites. With marsh-nesting species, such as Forster’s Tern and some Laughing Gulls, shifts due to tidal or wind flooding are usually within a local area or section of the marsh.

Two areas will serve as examples of colonial nesting birds along the northern Gulf of Mexico, one in Louisiana, and one in Texas. The Barataria-Terrebonne Estuarine system in southeastern Louisiana contains more than four million acres of wetlands and is vulnerable to wetland loss (Lindstedt 2005).

Over the last 50 years, this system has lost 47–57 km² (18–22 mi²) per year (Lindstedt 2005). In 2001, 24 species of colonial birds nested in the Barataria-Terrebonne Estuaries, with as many as 37 colonies of Great Egret, 31 colonies of Snowy Egret (likely in the same colonies), and 18 of Little Blue Heron (Lindstedt 2005). Tricolored Heron (Louisiana Heron) occurred in 10 colonies, Roseate Spoonbills occurred in only six colonies, and Reddish Egret was not reported (Table 12.15). Species associate with one another, so total colony size is much larger; the egrets usually nest together, along with herons and Night Herons.

Long-term trends also were examined in Galveston Bay Estuary from 1973 to 1990 (Gawlik et al. 1998). Approximately 50,000 nesting pairs of 22 species of colonial waterbirds used Galveston Bay annually since the 1970s, which represents about 30 % of the nesting colonial birds on the Texas coast. This area is also the most important wintering area for ducks and geese in the central flyway (Hobaugh et al. 1989). Laughing Gulls, a species with low annual variability, dominated the assemblage. In contrast, White Ibis and Sandwich Tern were both highly variable and abundant. Trend analysis showed that Roseate Spoonbill, Snowy Egret, and Black Skimmer declined significantly, while Neotropical Cormorant and Sandwich Tern increased significantly; the other 13 species showed no significant trends (Gawlik et al. 1998).

It seems clear from this review of the birds of the Gulf of Mexico that two types of information complement each other: local surveys and regional (up to Gulf-wide). Local surveys of one or two colonies are useful, especially when long-term data are available. Surveys from the same general area of the coast sometimes produce different results (Table 12.16), requiring careful interpretation in light of individual species characteristics. However, the two surveys were at different times, and may actually present a picture of regional shifts. Furthermore, when two different surveys from different areas produce the same result (Brown Pelican increased in both; Night Heron, Great Blue Heron decreased) it is likely to be real. In no case did a species show opposite trends. When the trends were not congruent (e.g., no trend, and increase), further investigation is necessary. For example, some species showed an increase from 1956 to 1992, but no trend thereafter. Data showing no trend should be examined further by conservationists.

Finally, understanding trends is a matter of using a “weight of evidence approach”—when all data sets indicate the same trend, it is likely real (Burger 2003). Conservation of colonial waterbirds is a matter of protection from human disturbance and predators, prevention of habitat loss, and insurance of sufficient foraging and nesting habitat, particularly for wading birds (Kushlan 2000a, b; Hafner et al. 2000; Pineau 2000; Clay et al. 2010). Active habitat management and augmentation are essential.

Migratory Passerines are often ignored when considering birds in the Gulf of Mexico because the focus is often on seabirds and waterbirds. Yet, the narrow band of wooded barrier islands and forested coastlines provides the departure point for Passerines crossing the Gulf of Mexico (Moore 1999). Each year billions of landbirds migrate between the northern and southern hemisphere, and many cross the Gulf of Mexico (Stevenson 1957; Moore 2000a, b). While it is an extremely important migratory pathway for Nearctic-Neotropical migrants, the Gulf of Mexico is also a formidable barrier for these migrants (Rappole 1995). Nearctic-Neotropical migrants are those that breed in the North Temperate zone and winter in the tropics (Shackelford et al. 2005), including mainly songbirds (Passeriformes), although they also include some shorebirds, terns, cuckoos, and others.

The objective of this section is to provide an overview of Nearctic-Neotropical migrants in the Gulf of Mexico and associated coastal lands, rather than in more upland habitats, such as wood plantations and bottomland hardwood forests (Wilson and Twedt 2003), and the coastal habitats of Veracruz and the Yucatán (Mackinnon et al. 2011). A number of monographs and edited books deal with neotropical migrants, including DeGraaf and Rappole (1995), Kerlinger (1995), Rappole (1995), Able (1999), Moore (2000b). Greenberg and Marra (2005), and further, Jahn et al. (2004) provide a system-wide approach to new world migration that is particularly applicable to the Gulf.

Migrants have three choices for flying between North America and Central/South America: (1) a circum-Gulf route through eastern Mexico and Texas, (2) a trans-Gulf route to the Yucatán Peninsula and the Mexican coast, and (3) a circum-Gulf route through Florida and West Indies (Stevenson 1957; Langin et al. 2009). Since migration takes place over a relatively small time scale, but a large spatial scale, different factors affect migration patterns. On a small spatial scale, habitat (amount and quality, prey availability) is critical, while on a broader scale, weather and winds become critical (Moore 2000a). Wind patterns are generally favorable for birds to migrate across the Gulf in the spring, usually determined by studies with radar (Gauthreaux 1971, 1999; Gauthreaux et al. 2006). Migration patterns are not static, but shift from year to year and season to season, depending upon prevailing winds (Barrow et al. 2005).

Analyzing data from 10 radar stations from Key West, Florida to Brownsville, Texas, Gauthreaux et al. (2006) showed that in the spring: (1) northbound migrants approached the northern Gulf Coast at between 1,000 and 2,500 m above ground; (2) the longitudes of peak arrivals were similar over the 4-year period (near longitude 75° west, northern Texas/western Louisiana); (3) wind trajectories over the Gulf of Mexico had relatively little influence on the longitude of peak arrival; (4) the longitude where the greatest density of trans-Gulf migrants arrived on the northern coast was relatively constant from year to year; and (5) on occasion, strong winds or storms displaced migrants, but migrants seemed to have a preferred route they followed. These conclusions suggest that conservation efforts should concentrate on the preferred routes and landing locations. These findings are intriguing and suggest the potential to develop conservation priorities for suitable habitat for northbound Nearctic-Neotropical migrants, especially when coupled with data from birds fitted with geolocators.

Neotropical migrants face several decisions with respect to the Gulf of Mexico, including which route to follow, when to migrate, where to make landfall before crossing the Gulf, where to make landfall after crossing the Gulf, and how long to stop at stopovers on either side of the Gulf. Passage across the Gulf is long, and birds often arrive in the Louisiana northern Gulf Coast with little fat (Yong and Moore 1997), making coastal lands critical for increasing fat stores and continued survival. Peak numbers of spring Passerine migrants occur from mid-April to early May, and radar studies indicate that nearly all the Passerine migrants arrive from directly over the Gulf of Mexico (Gauthreaux 1971). A bad storm or hurricane can kill 40,000 migrants on one day, if it occurs during a peak time when migrants are arriving from their northward flight across the Gulf (Wiedenfeld and Wiedenfeld 1995). The coastal habitats used by migratory Passerines are extremely important because estimates suggest that most Nearctic-Neotropical migrant Passerines are unable to reach northern breeding sites in a single flight without stopping (e.g., thrushes) (Yong and Moore 1997).

Passerines that are lean upon arrival often remain longer before departing for breeding grounds farther north (Moore and Kerlinger 1987). Length of stay in Louisiana after a trans-Gulf flight is related to fat-depletion upon arrival; lean birds (Parulinae warblers) remained longer than fat ones, but if weather is favorable, birds continue to migrate (Moore and Kerlinger 1987). For migrant Passerines using the northern Gulf Coast, suitable stopover habitat is a critical feature. Migrant densities were most strongly related to forest cover within a 5 km radius; this feature influenced where migrants made landfall (Buler et al. 2007). Indeed along the coast of Mississippi, northbound songbirds made landfall in resource-rich habitats within 18 km (11 mile) of the coastline (Buler and Moore 2011).

While radar is used to determine patterns of migration across the Gulf (Gauthreaux et al. 2006), data from banding stations are used to assess ecology of migrants, including timing (Moore et al. 1990; Marra et al. 2005), stopover duration (Moore and Yong 1991), and habitat use (Moore et al. 1990). Stable isotope techniques are used to connect the wintering and breeding grounds of Nearctic-Neotropical migrants (Hobson and Wassenaar 1997; Hobson et al. 2007; Hobson 2005; Kelly 2006b; Langin et al. 2009). The recent development of small geolocators makes it possible to follow migration routes of small birds, although they must be captured to remove the geolocator to obtain the data (Stutchbury et al. 2009; Burger et al. 2012b). This combination of techniques has revolutionized the understanding of migration, especially across the Gulf of Mexico and will continue to do so.

Niven and Butcher (2011) examined the status and trends of birds wintering along the U.S. northern Gulf of Mexico using the Audubon Christmas Counts from 1965 to 2011. Methods are described in the Methods section above. Their initial goal was to examine trends in light of the Deepwater Horizon oil spill, but there was not enough time between the spill and the counts to reflect the effects, if any, from the oil spill. To be on the conservative side, in Table 12.17 only the species with a significant decline of more than 2 % per year, and the species with a significant increase of over 2 %, are listed.

Niven and Butcher (2011) reported that among the 20 species that declined by at least 2 % per year, 13 had the center of their ranges in the Gulf, and four declined in the Gulf, but were increasing elsewhere (Canada Geese [Branta Canadensis], American Wigeon, Bonaparte’s Gull, Boat-tailed Grackle). These birds may be moving their wintering ranges farther north with global warming (Niven et al. 2009). Several species with winter ranges south of the northern Gulf of Mexico coast also declined (Eared Grebe [Podiceps nigricollis], Wilson’s Plover, Long-billed Curlew, Western Sandpiper, Red Knot, Black Skimmer and American Bittern [Botaurus lentiginosus]). Remarkably, these were mainly shorebirds, reflecting a general decline in shorebirds worldwide (Withers 2002; Morrison et al. 2006). Surprisingly, Canada Geese showed the greatest decline.

While a 2 % per year increase or decline may not seem significant in terms of overall population dynamics, it is when an average of 2 % per year change for 40 years. Second, although there are methodological and interpretational difficulties with Christmas Bird Count data, the results are both consistent and robust over a long period of time. And finally, the changes make sense in terms of possible effects of global warming, and threats to birds that use coastal beaches (habitat losses, erosion, human disturbance, pets, and pollution).