In many bird species, the sexes are morphologically distinct. Often this dimorphism is the result of sexual selection, but in some cases natural selection has acted to reduce competition between the sexes for food or broaden the foraging range of the species or both. Shaffer et al. investigate the biomechanics of sexual dimorphism in the wandering albatross from the Crozet archipelago in the southern Indian Ocean. In this species, females and males forage in different oceanic zones; females prefer subtropical and tropical waters, and males prefer the sub-Antarctic and Antarctic zones. Males were 20% heavier than females but possessed only 7% more wing area. Hence, wing loading in males is greater. These differences may reflect adaptation to the different wind regimes in the two zones, with greater wing loading being more advantageous in the windier Antarctic conditions. -- AMS
Funct. Ecol. 15, 203 (2001).
