Bill size in relation to position in the colony in the Chinstrap Penguin

In most seabirds, breeding success can be related to the ability to obtain a suitable nest-site within the colony, and this may result in competition for the limited number of available sites. Thus, if nest-sites vary in qual ity, individuals of the same sex are expected to compete for access to the highest quality nest-sites to enhance their own fitness. It is therefore ex pected that intrasexual competition would result in a correlation between s ize in the competing sex, or the size of a trait used as a weapon, and nest duality. Chinstrap Penguins (Pygoscelis antarctica) fight with other consp ecifics using the bill as a weapon. If bill size provides an advantage for intra-specific combat, rye would expect stronger bills in males occupying t he best nest sites. We studied patterns of some adult morphological traits in relation with nest position in a colony of Chinstrap Penguins. Bill morp hology was related to nest position in the colony, with individuals occupyi ng the central positions having the deeper bills. This relationship was fou nd in both sexes. Our data suggest that competition for position within til e colony is not an important factor involved in the sexual dimorphism shown by the Chinstrap Penguin.