hypothesis for the role of the bill overhang in preening. (a)
the bill overhang generates a shearing force sufficient to damange
lice as the lower mandible moves forward slightly during preening;
(b) straight mandibles can only exert a relatively weak vertical
force, by comparison.
Clayton, D.H. and B.A. Walther, 2001. Influence of host ecology
and morphology on the diversity of Neotropical bird lice.
preening hypothesis was confirmed experimentally in another recent
Clayton, D. H., B. R. Moyer, S. E. Bush, D. Gardiner, B. Rhodes,
T. Jones and F. Goller. 2005. Adaptive significance of avian
beak morphology for ectoparasite control. Proceedings of the
Royal Society of London Biological Sciences.