Some relationships between food and breeding in the marine Pelecaniformes

David Lack stimulated me to look at seabird ecology from an evolutionary viewpoint and to become particularly intrigued by the phenomenon of ‘holistic’ adaptation, which he chose as the theme of his Presidential address to the 1966 International Ornithological Congress. As soon as the adaptive significance of one trait, morphological, ecological or behavioural begins to emerge, it becomes apparent that it is part of a complex adaptive web. Perhaps the single most influential selection pressure is food. Lack built massively on this foundation, basing his theories about reproductive rates and the control of populations in higher animals on the concept of direct, density-dependent competition for food (Lack, 1954; 1966; 1968). In this chapter I trace some of the ways in which, in the Pelecaniformes, feeding habits have determined breeding strategies. The latter include the timing of breeding (the seasonal timing, the degree of synchronisation and the frequency), the lengths of the components of the breeding cycle, brood size and the age of first breeding. Are they all adapted towards the maximum production of young? In pursuing this theme I will stress social (behavioural) stimulation of breeding, which can be very important but which Lack seemed, to me at least, to underestimate. Although he removed some of the ambiguities in Darling’s early work on social factors he did not undertake research into them, or exploit the potential for detailed etho-ecological work on social stimuli and breeding success, of the Tinbergen — Lack axis, even though the results would have been highly germane to his great interest in recruitment.