Morphometric differences in two populations of Malvinas skua Stercorarius antarcticus

GRAÑA GRILLI, M.; MONTALTI, D

Campos do Jordao, Brasil

Congreso; 25th International Ornithological Congress; 2010

International Ornithological Union

Skuas are birds characterized by presenting a high fidelity to the pair and the breeding site, for this reason it is probable that far away populations of the same species present some degree of differentiation on their morphological characteristics. The discriminant function analysis (DFA) is a useful technique to differentiate individuals of different species and sexes from their morphological measures. In this case it was applied with the aim of developing functions which would enable us to differentiate the individuals of two different populations. We worked on Malvinas skua, Stercorarius antarcticus antarcticus, from the populations of Malvinas Islands and Argentinean Patagonian coast. Measures of culmen, bill height and width, tarsus and wing chord were used, from alive and museum individuals of both populations (Malvinas Islands, n = 24; Patagonia, n = 6). Only the bill height and width measures presented significant differences between populations, because of that they were the ones used in a DFA. This analysis generated a function which let us assign correctly the origin population with a 90 % of certainty. Despite the small number of the sample, this study highlights the occurrence of some morphological differentiation between individuals of two populations of the same subspecies, possibly originated by the isolation between both. Also, it gives a tool that could be applied to the determination of the breeding site of individuals found in other areas of their distribution.