| General Species Description: |
Reproduction Comments:Courtship behavior includes chases, vocalizations, and sometimes presentation of a fish to the female by the male. Lays eggs mostly in May-June (July-August nests probably are renests). Renesting may occur after egg loss associated with heavy rains and/or flooding (Jernigan et al. 1978, Blus and Prouty 1979). Clutch size usually is 2-3 (most often 2 in California, New York, and Mississippi), rarely up to 4-5 (Hardy 1957, Swickard 1974, Houde 1977, Hays 1980, Faanes 1983). Incubation usually lasts 20-25 days (also reported as 21-22 days), by both sexes but mostly by female. Hatching success varies greatly and is affected by factors such as weather, tides, predation, and human disturbance; may be high under optimal conditions. Young are tended by both parents, leave nest after a few days, brooded for several days, fly at about 3-4 weeks, dependent for a few weeks more. Reproductive success rarely exceeds one chick per pair (Kress et al. 1983). First breeds generally when about one year old, sometimes not until two years old (Massey and Atwood 1981). Maximum known natural longevity 21 years (Massey and Atwood 1978, Clapp et al. 1982). In recent years, colonies generally have included not more than 20 pairs, sometimes up to about 75 pairs (Ehrlich et al. 1992), rarely up to several hundred pairs. Colony may be divided into subcolonies (Massey 1974).
Ecology Comments:In California, usually nests in same area in successive years; tends to return to natal site to nest (Atwood and Massey 1988). On Long Island, New York, tends to nest in same area in successive years if physical conditions are conducive to nesting (MacLean et al. 1991).
NON-BREEDING: usually singly or in small loose groups; in larger flocks when migrating. Foraging may occur singly, in pairs, or in small flocks (Erwin 1978).
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