Patterns in the abundance of avian lice (Phthiraptera: Amblycera, Ischnocera)

This study examines the ecological factors expected to determine the abundance of lice on birds. The associations between avian body mass and avian sociality as selected environmental variables and the arithmetic mean of louse abundance per bird individual are evaluated across bird species. Rough data were obtained from the literature. Using host species as statistically independent observations, louse abundance correlates positively with avian body mass. This correlation is not a phylogenetic artefact, being also found after controlling for effects of host phylogeny. Three non-exclusive hypotheses might explain this correlation: (1) larger birds may provide larger 'habitat islands' enabling more lice to coexist; (2) larger birds may provide more topographic refugia for lice to evade host preening and grooming; and (3) more longevity of 'habitat islands' thus reducing the decimating effects of transmission. Contrary to expectations based on early anecdotal information, avian sociality had no significant effect on louse abundance either with, or without controlling for host-phylogenetic effects.