Nestling provisioning rates under the immediate risk of nest predation: Why less care is better.

PELUC, S. I.; GHALAMBOR, C. K.; MARTIN T. E.

Seattle, Washington

Congreso; 119th Meeting of the American Ornithologists' Union; 2001

Variation in parental care is thought to result from differences in the fitness costs and benefits associated with providing care. In birds wit h dependent young in the nest, parents must weigh the benefits of providing food to their offspring against the cost s of attracting the attention of nest predators. Thus, when faced with an immediate risk of nest predation, parents should temporarily decrease their nestling provisioning rat e to reduce the probability attracting attention to the nest. Here, we present a conceptual model that predict s how species that differ in their risk of nest predation should alter their nestling feeding rates when faced with an immediate risk of predation. We then tested this model experimentally by increasing the immediate risk of nest predation in 5 phylogenetically paired species occurring in Arizona and Argentina. Vocalizations of a common nest predator were broadcast near the nest to simulate the presence of predator. We found stron g support for predictions from the model; 1 ) all species reduced their nestling provisioning rate in response to the experiment, and 2) variation among species in response to the experiment was highly correlated with differences in the risk of nest predation across species. These result s suggest that differences in vulnerability to nest predation can accurately predict the behavioral response of parents t o a potential nest predator.