ИСТИНА

Global warming is particularly pronounced in the Arctic, however, its impacts on Snowy Owls are understood insufficiently. We used database of the Arctic Birds Breeding Conditions Survey (http://www.arcticbirds.net) to study changes in breeding status and the abundance of Snowy Owls in the Russian Arctic in 1989-2018. During this period warming trend was significant for May and June across all bioclimatic zones of tundra. We found that Snowy Owl breeding effort (a proportion of sites where owls bred in a given season) declined in 1989-2018. Owl breeding effort was strongly related to lemming abundance, however, the latter did not show significant decline over this time. At the same time, breeding effort showed negative relationship to May and June mean monthly air temperatures, which meant that a proportion of sites with breeding owls declined as temperatures increased. The best model of logistic regression with breeding effort as a binary response variable included both lemming abundance and mean June temperature as explanatory variables. Thus, a decline in owl breeding effort in 1989-2018 is, probably, explained by increasing June temperatures, rather than by change in lemming abundance. The abundance of owls was measured on a rank scale with 3 categories, low, average and high. The abundance of breeding owls showed a significant decline in 1989-2018 (ordinal logistic regression), positive relationship to lemming abundance and no significant relationship to early summer temperatures. The abundance of non-breeding owls did not show a declining trend in 1989-2018, was weakly related to lemming abundance and not related to mean May temperatures. This may be partly explained by the fact that in all years non-breeding Snowy Owls occurred in low numbers at a majority of sites. However, negative relationship of non-breeding abundance to mean June temperatures was found. Thus, increasing June temperatures were, probably, responsible for long-term decline in the breeding effort of Snowy Owls in the Russian Arctic, while factors responsible for decline in breeding abundance still need to be investigated.