Comparisons of Nest Defense Between Male and Female Blue-headed Vireos
Abstract-- This study was conducted to determine which sex of the blue-headed vireo (Vireo solitarius) shows greater nest defense during incubation and nestling stages. Since both sexes in this species share parental duties throughout the breeding cycle, both would be expected to face equal costs of nest predation and benefits of nest defense. In order to compare nest defense of males and females at early and late stages of nesting, a stuffed, mounted blue jay was presented at nests in which there were either eggs or nestlings. Latency to arrive, scold, and dive, as well as number of dives, were compared for each sex at each nesting stage. There was no significant difference between the behavior of males and females with a Fisher exact test or analysis of variance. A power analysis revealed that these tests had relatively low power, ranging from 24 to 60 percent, to detect a difference had one existed. In this study population, the sexes perform equivalently in defense. More specifically, because the male and female blue-headed vireo make similar investments, and therefore stand to gain equally, they take equal risks in protecting their nest. These results support the idea that evolutionary costs and benefits shape the behavior of individuals.
Biological And Life Sciences, Biology, Ecology, Natural History
Journal of Young Investigators