At a breeding site for wandering albatrosses in the Crozet Islands, Shaffer made detailed measurements of body size, wingspan, and wing surface area on 56 birds, including adults and fledglings of both sexes. On average, males are heavier than females and the length and surface area of their wings are greater. In addition, he found that projected wing loading in fledglings is lower than in adults. These findings are consistent with differences in wind conditions in the regions where birds of different sexes and ages are known to forage, Shaffer said. The higher wing loading in males means they require higher wind speeds to stay aloft without flapping their wings.
Females tend to forage in subtropical and tropical waters to the north, where winds are lighter.
Fledglings forage farther north in even lighter wind conditions than adults of either sex. Albatrosses in general have high wing loading compared to most other birds. Their long, slender wings minimize drag and enable albatrosses to ride the wind while expending very little energy to stay aloft. The wandering albatross is the largest of the albatrosses and has the longest wings of any bird, with wingspans commonly exceeding 10 feet. Weimerskirch and his colleagues, including Shaffer and Costa, showed in another study published last year that the metabolic rate of a wandering albatross in flight is not much greater than when the bird is sitting on its nest.