FOOD AVAILABILITY OR NEST PREDATION RISK DURING INCUBATION AND NESTLING STAGES. CAN A SINGLE FACTOR EXPLAIN ALL THE VARIABILITY IN REPRODUCTIVE BEHAVIOR?

PELUC, SUSANA, ; VERGARA TABARES, DAVID; ; LUCZYWO, AYELEN; ; DIAZ, AGUSTIN

Vancouver

Congreso; North American Ornithology Conference V; 2012

AOU

Nest predation has been extensively recognized as an important force in avian life history evolution, shaping life history traits. Food availability has also been proposed as another selective force affecting life history trait diversification. Yet although nest predation risk and food availability often covary in nature and may even have interacting effects, they are frequently studied as mutually exclusive drivers of life history diversification. Using two open cup nesting passerines from the southern hemisphere as model systems (Turdus chiguanco, Saltator aurantirrostris) we test two classic hypotheses for the causes of divergence in avian life histories with a robust 2 x 2 factorial design experiment. 24 Nests of each species were randomly assigned to one of four treatments: Predator presentation (taxidermic mounts and vocalizations in the vicinity of the nest), food supplementation, Predator presentation + food supplementation or control. Predator presentations as well as food supplementation were administered during 12 days for at least 5 hours, during both incubation and nestling stages. On each nest we examined the effect of treatments on incubation patterns, feeding rates, and nestling growth rate. Our results suggest that non of the factors tested is likely to explain variation in all life history and behavioral traits by itself. We will discuss how these two strong ecological factors rather interact to shape reproductive behavior and investment in passerine species from the southern hemisphere.