Escape from predators and genetic variance in birds

Predation is a common cause of death in numerous organisms, and a host of anti-predator defenses have evolved. Such defenses often have a genetic background as shown by significant heritability and micro-evolutionary responses towards weaker defenses in the absence of predators. Flight initiation distance (FID) is the distance at which an individual animal takes flight when approached by a human, and hence it reflects the life history compromise between risk of predation and the benefits of foraging. Here we analyzed FID in 128 species of birds in relation to three measures of genetic variation, band sharing coefficient for minisatellites, observed heterozygosity and inbreeding coefficient for microsatellites in order to test whether FID was positively correlated with genetic variation. We found consistently shorter FID for a given body size in the presence of high band sharing coefficients, low heterozygosity and high inbreeding coefficients in phylogenetic analyses after controlling statistically for potentially confounding variables. These findings imply that anti-predator behavior is related to genetic variance. We predict that many threatened species with low genetic variability will show reduced anti-predator behavior, and that subsequent predator-induced reductions in abundance may contribute to unfavorable population trends for such species.