Effects of Ectoparasites on Reproduction of Their Swallow Hosts: A Cost of Being Multi-Brooded

Many birds are negatively affected in terms of reproductive success by the presence of ectoparasites in their nests. We hypothesized that the negative effects of ectoparasitism on reproductive success would be a direct function of the number of clutches laid because of a seasonal increase in ectoparasite populations. Ectoparasites would negatively affect each clutch and the total effect of parasitism on annual reproductive success should therefore be relatively larger with an increasing number of clutches. This prediction was tested by fumigation of nests of swallows Hirundo rustica either following completion of the first clutch, completion of all clutches or by keeping nests as controls