The Incidence and Effects of Ticks on Migrating Birds at a Stopover Site in Maine

Abstract

Ticks are common ectoparasites on birds, but little work has examined the effects of ticks on migrating birds. In this study, we examined the incidence of ticks on migrants during spring and fall migration on Appledore Island, ME. Because ticks are not indigenous to the island, birds with ticks are very likely to have transported them from elsewhere. During spring, 2.4% of migrants captured were parasitized by at least one tick, whereas during fall, 0.6% of migrants were parasitized by ticks. These trends occurred in several of the commonly captured species, although there was substantial variation among species. The average number of ticks per infested bird did not differ between the seasons among our commonly captured species. Males and females had similar tick loads within most species. We did not find a consistent pattern of difference in condition (fat and mass) among birds that were parasitized by ticks compared with those that were not. Furthermore, comparison of birds parasitized by ticks with those that were not indicated no significant difference in either the recapture rate or the stopover length between these two groups. Although parasites may greatly impact the fitness of individual birds, our results suggest that ticks are not impacting the species of migrant birds that use this stopover site during migration.