Trends in Arctic-nesting loon (Gavia spp.) populations in North America

Abstract

Several species of loons (or divers; Gaviidae) breed in Arctic Canada, and concern has been raised about their changes in abundance in light of threats such as bycatch and at-sea industrial development. These loons are not well monitored, but we gathered localized count data for three Arctic-nesting loons (Pacific loon Gavia pacifica, red-throated loon G. stellata, and yellow-billed loon G. adamsii) from multiple sources and estimated mean annual population change to estimate species-specific trends over varying time periods. Most breeding ground information between 1996 and 2022 suggested stable numbers for each species, although data were scarce for yellow-billed loon. Trends during the non-breeding season from 1966 to 2021 were estimated for red-throated and Pacific loons from the Christmas Bird Count, a citizen science general bird count, and suggested overall stable or increasing numbers, despite some substantial regional differences. Again, yellow-billed loon numbers were not captured well during the non-breeding season. Aerial winter waterfowl surveys on the east coast of North America (2008–2011, 2014) showed positive trends for red-throated loons for most locations north of 38° latitude and stable trends elsewhere. The paucity of both breeding and non-breeding count data for yellow-billed loons is unfortunate, as this species is found in high numbers in fishing gear in the Arctic. Overall, the limited available data do not suggest that loon populations breeding in the Canadian Arctic have experienced extensive declines, but monitoring of yellow-billed loons should be a priority.