ROGERS, S.A.*; CORBIN, C.E.; WASSMER, G.T.; Bloomsburg University of Pennsylvania; Bloomsburg University of Pennsylvania; Bloomsburg University of Pennsylvania: Prevalence of nest ectoparasites is independent of group size and nest density in barn swallows (Hirundo rustica)

Coloniality has been suggested to have both costs and benefits. A potential cost of living in a group is high infection rates of ectoparasites. One prediction of this hypothesis is that when group size increases, ectoparasite load will also increase. Several studies have suggested that such a relationship exists. We used barn swallows to examine the relationship between ectoparasite load, group size, and nest density across eleven sites in Pennsylvania. We measured group size by counting active nests and calculated density from average nearest neighbor distance. Ectoparasites were detected by standard methods in each active nest throughout the entire 2005 breeding season. The proportion of infected nests was regressed against group size and group density. Ectoparasite load was not dependent on either nest density or group size � a finding contrary to other studies on colonial passerines. These results suggest that chance events and/or density independent factors are important in determining ectoparasite prevalence.