Try and try again: Nest predation favors persistence in a neotropical bird

Abstract

Successful reproduction for birds in systems with high nest predation rates may be explained by two alternatives. The first hypothesis is that nest-predation is avoided, perhaps by nest-site or territory selection, parental behavior and so on. This hypothesis renders the prediction that within-pair consistency, or repeatability, in nesting success occurs and is due to nest predation avoidance. The alternative hypothesis is that pairs vary in their ability to nest again following predation, and generates the prediction that differential reproductive success among pairs is due to renesting ability, not predation avoidance. To test these alternatives, nest success, renesting intervals, breeding season length, and nesting history were studied in the Western Slaty Antshrike (Thamnophilus atrinucha) in central Panamá. Reproductive success is low; with a survival rate of 0.91 day-1, only one in eight nesting attempts are successful and essentially all nest failures are due to nest predation. Pairs showed neither consistency in nesting success nor variation in nest predation avoidance. Renesting ability, however, varied among pairs and, following nest failure, experienced pairs renested 14 days sooner than inexperienced ones. On average, reduced renesting interval allowed time for an additional three nesting attempts year-1. Since only one in eight nests is successful and the average pair nests five times year -1, these additional nesting opportunities provide the margin necessary to increase the odds of successful reproduction to near certainty. While nest predation avoidance may explain nesting strategies, all nesting attempts are equally likely to fail. Instead, renesting ability is an important factor influencing differential nesting success, and is probably more important for tropical birds, where long breeding seasons permit several nesting attempts. © The Neotropical Ornithological Society.