A comparison of reproductive success in early and late breeding Sooty Terns (Sterna fuscata) in the dry tortugas

Evidence indicates that earlier-nesting birds are often older, choose preferred nest sites, and have greater reproductive success than those nesting later. The Sooty Terns at Bush Key appear to follow a similar pattern. The first birds arrive at the west end of the breeding grounds three weeks earlier than birds at the east end and behaviorally appear to be older and more experienced. The west birds settle in the more desirable habitats (the west end was cooler than the east end) and laid larger eggs, hatched larger chicks, enjoyed greater hatchability, fed their chicks at a lower frequency when they were young, and had greater reproductive success than birds in the east. This was accomplished through a combination of choosing physically and thermally more favorable habitat, which was more centrally located, being more persistent incubators and brooders, and, by nesting earlier, having larger, less-easily eaten chicks by the time avian predators arrived on the island.