Abstract
The ocean is swept by winds in regionally and seasonally predictable ways, and seabirds have been exploiting these patterns for millennia. Seabird use of wind energy is an under-appreciated aspect of seabird ecology. Using data from 114 cruises spanning the Southern Ocean, Peru Current, California Current and Equatorial Pacific from 1976 to 2006, we evaluate the effect of wind speed and direction on two key characteristics of seabird behavior, flight height and flight behavior. We used cluster analysis to partition 104 seabird species into morphological groupings based on degree of divergence in morphology from Pennycuick’s “standard seabird,” with subgroups evident among and within flappers, glide-flappers, and flap-gliders. Gliders, sea-anchor soarers and soarers showed no such divergence in morphology within their respective groups. Morphological grouping was in accord with foraging ecology, facilitating foraging behavior. Seabird flight height and behavior varied among groups and subgroups and changed as a function of wind speed and direction relative to travel, with the probability of more gliding and flying above 10 m increasing as wind speed increased. Most of the glide-flappers, flap-gliders and gliders, especially, would be highly vulnerable to offshore wind-generating facilities, as their flight heights bring them well within the blade-swept zone of typical turbines when winds are strong, and their more prevalent gliding makes them less maneuverable than flappers.