The role of wind fetch in structuring Antarctic seabird breeding occupancy

Avian breeding sites located along shorelines may allow easy access to aquatic food sources, but risk exposing birds and nests to high wind and wave action. One measure of exposure is wind fetch, the distance of open water over which wind can blow uninterrupted. By calculating fetch weighted by prevailing wind direction for breeding colonies of pursuit-diving seabirds in the Antarctic Peninsula, we show that different members of this guild have opposing relationships to coastline exposure. Gentoo Penguins Pygoscelis papua preferentially occupied more enclosed sites with lower fetch. Surprisingly, however, Chinstrap Penguins Pygoscelis antarcticus and Antarctic Shags Leucocarbo bransfieldensis appear to prefer more exposed sites. Although considerable research has been devoted to understanding Antarctic seabird habitat suitability, the role of wind and wave exposure has not been considered in depth, in part because comprehensive data on colony presence and absence have only recently been made available. We propose several mechanisms for why fetch may act to differentiate niches among this guild. These findings may increase our ability to identify suitable breeding areas for these and other near-shore breeding species as they respond to climate change.