Predation risk and nest-site selection in the Inca tern

• Published in: Canadian Journal of Zoology
• Main Authors: Velando, Alberto, Márquez, José C
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2002
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Inca; Falco peregrinus; peregrine falcon
• Online Access: http://dx.doi.org/10.1139/z02-091; http://www.nrcresearchpress.com/doi/pdf/10.1139/z02-091

Most tern species (Sternidae) are typically open-ground breeders; the Inca tern (Larosterna inca), however, breeds in crevices. This paper reports the first analysis of nest-site characteristics, predation rates, and breeding success in this species. We tested for evidence of natural selection on nest-site preferences in a colony subjected to high rates of predation by the peregrine falcon (Falco peregrinus). Characteristics of occupied sites differed from those of non-occupied sites. Terns selected sites with longer chambers, a greater number of cavities, and more overhead and lateral cover that were located close to the cliff edge. Predation was the main cause of breeding failure, and successful sites differed from unsuccessful sites, which is evidence for ongoing natural selection. Chicks at sites in larger crevices and more cavities remained at the site longer and were less likely to be depredated by peregrine falcons. Probably in response to the presence of predators, adults flew towards the colony in flocks, which "dissolved" at the cliff edge. Sites located far from the edge were more likely to be depredated and adults breeding there fed their chicks less frequently and, consequently, reared lighter chicks. The concordance between site preference and predation pressure on nest-site selection suggests that the use of non-preferred sites imposed a cost in the form of increased nest predation.