Distribution of Camus hemapterus in a starling colony

The distribution of the haematophagous fly Carnus hemapterus among starling (Sturnus vulgaris) broods was investigated in a nest-box colony. Prevalence of infection was 94% among broods and 69% among individual nestlings, while median abundance was 54 flies per brood (range 0-284 flies; n = 33) and 8 flies per individual nestling (range 0-117 flies; n = 140). Parasites exhibited an aggregated distribution among starling broods. Carnus hemapterus populations changed significantly during the development of nestlings: fly abundance increased rapidly after nestlings hatched, peaked 5-8 days after hatching and decreased thereafter. The proportions of winged flies (assumed to be the transmissive form) and the proportion of male flies decreased with increasing nestling mass. Measures of within-colony spatial position of nests were not related to mean brood abundance, proportion of winged flies or sex ratio of the flies. Parasite abundance did not correlate with mortality rate or growth rate of nestlings. In conclusion, nestling developmental stage was the only significant predictor of variation in C. hemapterus populations in this starling colony.