Diving Depths of Shearwaters

Maximum diving depths were measured for shearwaters breeding on Cousin Island, Seychelles. Eighty-three percent of 23 Wedge-tailed Shearwaters (Puffinus pacificus) dived, and their mean maximum depth was 14 m (SD = 23 m, range 1–66 m, N = 19). All Audubon's Shearwaters (P. lherminieri) dived, and their mean maximum depth was 15 m (SD = 12 m, range 6–35 m, N = 7). These data contradict the hypothesis that tropical shearwaters should not specialize in underwater foraging. They are capable of exploiting deep prey unavailable to most other tropical seabirds. Five Puffinus species (temperate and tropical) attained allometrically scaled maximum depths comparable to those of penguins and alcids.