Relationship of human intrusion on avian body mass: Do recreationists hinder birds’ abilities to acquire fat during migration?

Many North American landbirds undergo biannual migration, which is energetically costly. Quality stopover sites are crucial to avian survival, as they provide opportunities to quickly replenish fat stores, rest, and avoid predation. One component of habitat quality that is often overlooked is the level of pedestrian activity, which birds interpret as potential predators. If intrusion levels are high, birds will flush readily and may not adequately restore energy reserves, which hinders successful migration. I compared body mass index between birds at different intrusion levels, testing the hypothesis that birds near continuous intrusion are less capable of replenishing body fat. Results between migratory guilds indicate long-distance migrants require areas of low intrusion to sufficiently acquire fat stores. In contrast, resident species are able to replenish body mass despite human intrusion. Since Neotropical migrants show increased sensitivity to human presence, conservation measures should focus on reducing pedestrian activity for quality stopover habitats