Life history differences between populations of a neotropical thrush: nest predation or food limitation?

FERRETTI VALENTINA; LLAMBÍAS PAULO E; MARTIN, THOMAS E.

New Orleans

Congreso; 3rd North American Ornithological Conference; 2002

Ever since Lack first mentioned that birds would rear as many young as they can nourish, food limitation has been the major explanation for the evolution of avian life history traits. However, recent studies have shown that variation in some life history traits is associated to a variation in nest predation among species, but the importance of nest predation in shaping avian life history traits has generally been considered secondary to food limitation. Here, we examine both hypotheses, on 2 populations of a neotropical thrush that differ in nest predation risk. Our results show that the population with higher nest predation has smaller clutch sizes, lower parents´ visitation rates, both during incubation and nestling periods, and faster nestlings´ growth rates. Moreover, the population with higher clutch sizes had significantly higher starvation rates, when clutch size was standardized between populations to 3 eggs and synchronous hatching. Thus, we are able to say that nest predation risk plays a major role in shaping differences in life history traits between these populations.