Comparative ecology of seabirds in the Galapagos Archipelago

If the numbers of birds are regulated by availability of food, as the evidence suggests, species which live together in the same area must have evolved means of reducing interspecific competition for food. They might feed in different places, at different times, in different ways, or on different prey (Huxley, 1942); any two species may differ in more than one of these ways. How these separations are brought about may be difficult to determine because they may take effect only when food is short, the species overlapping in almost all respects when food is plentiful.