Distribution and abundance of water birds and seabirds in some areas of the southwestern Kara Sea in the summer-autumn period 2015–2020

Abstract

The southwestern Kara Sea is a scarce studied area in terms of summer-autumn migrations and feeding nomadism of water birds and seabirds. Its shelf includes promising areas for extraction of hydrocarbon raw materials and intensification of navigation along the Northern Sea Route, which makes it necessary to carry out constant monitoring of birds in the area of possible negative effect of those factors. In August–September 2015–2016 and 2018–2020 and in late September–first and second decades of October 2017, bird counts were carried out in the southwestern Kara Sea. Method of ship transect census was applied to obtain the abundance of individuals per 1 km². For this water area, 28 species of birds representing 7 families were identified (Gaviidae, Sulidae, Procellariidae, Anatidae, Laridae, Stercorariidae, and Alcidae), including 6 species of conservation status. For the group of water birds, the data obtained in August–October are most detailed for the black-throated diver, long-tailed duck, and king eider (Gaviidae and Anatidae). Prior to autumn migration (August), their abundance increased in the shallow area adjacent to the coast, later followed by their dispersal to deeper areas west of the Yamal Peninsula. In coastal shallow areas, the population density during the period of the most active colonization of this biotope is as follows (ind.·km−2): (0.17 ± 0.036) for the black-throated diver, (4.87 ± 1.2) for the long-tailed duck, and (2.1 ± 1.25) for the king eider. Presumably, the values are significantly higher for all three species at shorter distances from the coast not examined from the vessel. Other species of the group of water birds (the red-throated diver, Steller’s eider, dark-bellied brant goose, European white-fronted goose, and bean goose) are rare in open waters and, apparently, are mainly confined to a narrower coastal zone during the entire summer-autumn period. The same indicator of abundance of migratory seabirds (Procellariidae, Laridae, Stercorariidae, and Alcidae), calculated for the entire water area of the survey site, averaged for 5 years for August–September (ind.·km−2): (0.078 ± 0.026) for the fulmar, (0.067 ± 0.014) for the glaucous gull, (0.061 ± 0.016) for the black-legged kittiwake, (0.025 ± 0.015) for the Arctic tern, (0.066 ± 0.0049) for the Heuglin’s gull, (0.046 ± 0.0074) for the pomarine skua, (0.014 ± 0.0023) for the Arctic skua, (0.0039 ± 0.00095) for the long-tailed skua, (0.16 ± 0.094) for the Brünnich’s guillemot, and (0.0026 ± 0.0012) for the black guillemot. In late September and October, the abundance of the black-legged kittiwake, fulmar, and Brünnich’s guillemot slightly decreases or remains at the level of September one, while the abundance of the black guillemot increases by 7 times. The Arctic tern, Heuglin’s gull, and long-tailed skua disappear from the water area. The glaucous gull, pomarine skua, and Arctic skua become much rarer or almost disappear (5-, 40-, and 30-fold drop in abundance, respectively). In general, in the long-term aspect, the fulmar, three Stercorariidae species, the glaucous gull, black-legged kittiwake, Arctic tern, and black guillemot colonize the entire survey site. Interestingly, for the fulmar, black-legged kittiwake, and glaucous gull, uneven distribution is recorded in some years, which is expressed in significant (3 to 17 times) differences in abundance between large (about 25 thousand km²) spots of the studied water area. During their entire stay at the survey site, the Heuglin’s gull and Arctic tern are mainly confined to coastal shallow areas; there, up to 80–90% of the total abundance of individuals in the studied water area is concentrated during periods of seasonal maximum. On the contrary, the Brünnich’s guillemot avoids shallow areas (depth of < 50 m). Rare species are vagrant ones (the northern gannet, black-headed gull, European herring gull, and common gull), those found in the peripheral area of their common range (the great skua and grey petrel), and those considered rare at the present stage of the existence of their populations (the white-billed diver). Also, rare species are the birds with insufficiently studied main habitat (the velvet scoter, Steller’s eider, dark-bellied brant goose, bean goose, and European white-fronted goose) and seasonally rare ones (the little auk).

Keywords

• kara sea
• seabirds and water birds
• migrations
• nomadism
• annual and seasonal population dynamics