Predicting at-sea habitat suitability of Alcids in the San Juan Islands, Washington

Abstract

Important bird areas (IBAs) are an integral part of effective seabird conservation, however, IBAs require a clear understanding of the spatial and temporal distribution of birds. To determine potential IBAs in the San Juan Archipelago, I developed species distribution models for three Alcids species (Pigeon Guillemots [Cepphus columba], Rhinoceros Auklets [Cerorhinca monocerata], and Marbled Murrelets [Brachyramphus marmoratus]) based on at-sea survey observations for May-July 2013 and May-July 2018 and oceanographic variables (e.g., distance to shore, chlorophyll a concentration). Results indicated areas in the southern Lopez Island were of high habitat suitability for all three species but is currently not listed as an IBA. Distance to shore was a consistent predictor for suitable habitat but importance of environmental factors shifted temporally. The predictive maps for Marbled Murrelets showed the smallest area of suitable habitat in the region, whereas both the Pigeon Guillemot and Rhinoceros Auklet and several areas with highly suitable habitat. The preliminary results from my study indicate that San Juan Archipelago has several areas that should be considered for designation as IBAs.