Colony Visitation Behavior And Breeding Ages Of Sooty Terns (Sterna Fuscata)

The apparent regulation of population size in seabirds has been a topic of recent research by several ornithologists (e.g. Ashmole, 1963b; Harris, 1969a, b, c; Nelson, 1965, 1966, 1969a, b; Rowan 1965; and Lack, 1968). These authors theorize that major limiting factors are either availability of food or nest space and that consequently a direct or indirect extrinsic influence on population size exists through selected regulation of clutch-size, mortality, deferred maturity, long parental care, long breeding cycles, and social behavior. In contrast, Wynne-Edwards (1955) suggests that colonial seabirdsh ave intrinsic responsesto varying food supplya nd that by collective social mechanisms they maintain population sizes compatible with existing food supply. He further suggestso ne methodof maintaining appropriate numbers is through regulation of colony size, and he implies that this regulation is often enforced by established breeders preventing young individuals from securing and utilizing space in a colony (1962: 557). Ashmole (1963b) argues thatthe Wynne-Edwards hypothesis requires limited nesting space or defense of unoccupied areas in colonies that are not filled to capacity.

BRIAN A. HARRINGTON, Journal of Field Ornithology: Vol. 45, No. 2,