Eugenia V. Bragina, Martin D. Robards, Daniel J. Rizzolo, Randall J. Friendly, Alexander I. Matsyna, Ekaterina L. Matsyna, Aleksandr A. Matsyna, Polina S. Smagina, Konstantin S. Maslovsky
Arctic 2026; 79(2)
The Indigirka River Delta (Republic of Sakha, Yakutia) has been recognized historically as an important breeding area for numerous Arctic bird species and has the largest breeding concentration for the threatened Spectacled Eider (Somateria fischeri). However, the most recent peer-reviewed studies from this region date to the 1990s, and contemporary information on breeding conditions is lacking. Given the continued decline of Spectacled Eider populations, updated data from this key breeding area are critically needed. To assess current breeding status of Spectacled Eiders and the overall bird community at this site, in 2022 to 2024 we repeated ground-based surveys conducted in 1994 – 95. Spectacled Eider arrival occurred several days earlier than in the 1990s, on 28 May to 1 June, instead of 6 June, though nest initiation timing was comparable. Reproductive performance over the three years of study (2022 – 24) was relatively low: cumulative nest survival over the 24-day incubation period was 0.44 (95% CI 0.36 – 0.52), below values reported from Alaskan populations. Consistent with earlier results, coastal islands provided habitat supporting higher nest survival. In the interior, but not at the coast of the Indigirka River Delta, daily nest survival increased with nest age. Minimum daily temperature had a negative effect on nest survival. Our results are consistent with prior surveys in the 1990s, confirming low reproductive success for Spectacled Eiders at this key breeding ground. With respect to the broader bird community, we recorded notable changes since the 1990s in species representation. Four species previously reported were not detected, 10 species were new to the area, and 10 species were newly confirmed breeding.
