Regression between global population size and overall lice species richness. Lice species richness was controlled for sampling effort using residuals from the Google Scholar citation counts. A, Regression for non-phylogenetic analysis of species values (slope = 0.41, F = 16.82, d.f. = 301, P < 0.0001). Pelecaniiformes are represented by blue squares, Charadriiformes by red triangles and Procellariiformes by green crosses. B, Regression using independent contrasts (slope = 0.43, F = 33.4, d.f.= 196, P < 0.0001).