Relationship of Host Coloniality to the Population Ecology of Avian Lice (Insecta: Phthiraptera)

Abstract

We test the hypothesis that avian social system (territorial vs. colonial) has an impact on the ecological characteristics of avian lice. We compared the louse loads of two congeneric host species, the territorial hooded crow (Corvus corone cornix L.) and the colonial rook (C. frugilegus L.). Each species harboured the same five genera of lice ; one species of louse was shared, while the other four species on each host were host-specific. More rooks harboured Myrsidea, Philopterus, Brueelia and Allocolpocephalum spp. than crows. Rooks harboured more species-rich louse loads than crows. Louse loads were also more diverse on rooks than on crows. The frequency distributions of lice on rooks were less aggregated than on crows. Sex ratios of lice were less biased on rooks than on crows. Biased sex ratios were correlated with the subpopulation size of lice on individual hosts, making it necessary to control for subpopulation size in comparative analyses. These findings may result from the increased frequency of horizontal transmissions via increased body-to-body contacts among colonial rooks, compared to territorial hooded crows.