Long-tailed Duck (Clangula hyemalis) ecology: insights from the Russian literature. Part 1: Asian part of the Russian breeding range

Long-tailed Ducks (Clangula hyemalis) nest in tundra habitats and are marine birds outside of the breeding season. These sea ducks are subject to negative impacts and threats throughout their annual cycle, and the population wintering in the Baltic Sea has declined dramatically in recent decades. To understand their life history and the drivers of population decreases, the ecology of Long-tailed Ducks needs to be understood in their breeding and wintering habitats. Most of the birds wintering in the Baltic Sea breed in northern Russia. Here, we reviewed the Russian literature on the Long-tailed Duck in the Asian part of the Russian breeding range (from Yamal to North East), with respect to their distribution, density, breeding and feeding biology. We summarized information from 74 Russian sources, with a strong representation of field surveys and ecological studies in the 1970s and 1980s. The data show a comparable overall breeding biology and timing within the area and compared to the European part of the breeding range. Considerable differences in the densities between sites and years were observed, but the underlying drivers of these differences are not yet understood. Overall, the proportions of non-breeding birds were high in most reports, but further studies are needed to understand the potential impact of changes in the breeding habitat on population trends. The data summarized here provide a comprehensive database for carrying out repeat surveys and ecological studies to improve understanding of population trends and their underlying ecological basis.