Shorebird use of western Hudson Bay near the Nelson River during migration, with a focus on the Red Knot

Long-distance migratory shorebirds are vulnerable to stressors throughout their annual cycle, including during migration when they must rely on a limited set of stopover sites to refuel. The rufa subspecies of Red Knot Calidris canutus has shown drastic population declines in recent decades and is listed as Endangered in Canada and Threatened in the United States. Recent evidence from light-level geolocators suggested that the subspecies might use a previously unknown remote stopover site on the west coast of Hudson Bay near the Nelson River, but total numbers of knots using the area and the specific locations and habitats used were unknown. In spring 2014, we performed ground and aerial surveys of coastal areas surrounding the Nelson River to assess shorebird use and abundance. In addition, we used radio telemetry to investigate migratory connectivity between the Nelson River and an important stopover site at Delaware Bay, New Jersey. Red Knots were the second-most abundant species observed during ground surveys, and we counted a total of 4,259 knots during a two-day aerial survey, representing about 10% of the estimated rufa population. At least 16 knots with radio-tags out of 87 banded at Delaware Bay were detected near the Nelson River, suggesting strong migratory connectivity between the two stopover sites. Based on our observations of knots and other shorebirds, the site qualifies as an Important Bird Area (IBA) and Western Hemisphere Shorebird Reserve Network (WHSRN) site under several criteria. Understanding the potential impacts of threats in the area, including hydroelectric development on the Nelson River and overabundant Snow Geese Chen caerulescens caerulescens, is a critical next step in protecting the rufa subspecies from further declines.