Functional significance of sexual dimorphism in Wandering Albatrosses, Diomedea exulans

1. The investigation covered whether sexual dimorphism could affect flight performance in a manner that is consistent with differences in at-sea distr ibution of male and female Wandering Albatrosses, Diomedea exulans Linnaeus . Adult morphology was also compared to near-fledged chicks to assess wheth er morphological differences are consistent with different at-sea distribut ions of adults and fledglings. 2. Body girth, mass, wing span and area were measured on 24 females (16 adu lts and 8 chicks) and 32 males (20 adults and 12 chicks) breeding in the Cr ozet Archipelago. 3. On average, adult males had longer wings (4%, 311 +/- 4 cm) with 6.8% mo re area (6260 +/- 270 cm(2)), but were also 20.4% heavier (9.44 +/- 0.59 kg ) than adult females. As a result, wing loading in adult males was 12.1% gr eater than adult females. 4. When compared with adults, total wing area of chicks was lower resulting in higher wing loading because of the incomplete growth of chicks at the t ime measurements were collected. However, projected chick growth to fledgin g indicates that wing loading would be lower in fledglings than adults. 5. Because wing loading determines flight speed, it is conceivable that win dier regions of the sub-Antarctic/Antarctic are more optimal for male albat rosses because they have higher wing loading. Conversely, wing loading is l ower in adult females and fledglings, which could make them better adapted to exploit lighter winds of the subtropical and tropical regions. Thus, siz e dimorphism may have a functional role in flight performance that influenc es the at-sea distribution of adult and fledgling Wandering Albatrosses.