CLIMATIC AND OCEANOGRAPHIC INFLUENCES ON ISLAND USE IN 4 BURROW-NESTING ALCIDS

More than 2,000,000 pairs of burrow-nesting alcids breed along the Pacific coast of North America between 48-degrees and 55-degrees N latitude. Most occur in a few large colonies leaving > 98% of coastal islands unoccupied. There is considerable local variation in climate and oceanographic conditions, but such variation is in part predictable since it is largely attributable to regional orographic conditions and stable seasonal weather patterns. Here we examine colony-site location in four burrow-nesting alcids, Ancient Murrelet Synthliboramphus antiquus, Cassin's Ptychoramphus aleuticus, and Rhinoceros Auklet Cerorhinca monocerata and Tufted Puffin Fratercula cirrhata, with respect to variation in climate and oceanographic conditions. Colonies are located on islands in colder, more saline water, and are subject to less intense rainfall than non-colony sites. Drier nesting sites offer several potential advantages including reduced burrow erosion, low risk of flooding, and easier maintenance of burrow microclimate. Cold, saline water is associated with increased food availability while freshwater runoff is associated with decreased marine productivity.