Spatial distribution and habitat selection of Barrow’s and Common goldeneyes wintering in the St. Lawrence marine system

Our study addresses winter spatial distribution of Barrow's Goldeneyes (Bucephala islandica (Gmelin, 1789)) and Common Goldeneyes (Bucephala clangula (L.. 1758)) at the scale of the St. Lawrence marine system (estuary and northwestern gulf), eastern Canada. Our objectives were (i) to identify and compare the physical factors that control their distributions, (ii) to quantify the level of sympatry between the two species, and (iii) to compare their distribution patterns. We analyzed large-scale synoptic views of winter distribution of both goldeneye species obtained through helicopter-borne surveys. Habitat description was obtained through spatial analyses and remote sensing. Both species showed strong preference for the tidal zone and river mouths. A multiscale analysis showed a decreasing level of sympatry as spatial resolution was refined. The distribution of the Barrow's Goldeneye was more clustered compared with that of the Common Goldeneye, and Barrow's Goldeneye was repeatedly observed in the same few areas. A use-availability analysis identified the northern coast of the St. Lawrence estuary as the main wintering ground for Barrow's Goldeneye in eastern North America.