Пернатые хищники и их охрана (Oct 2018)
Long-term Monitoring of the Steller’s Sea Eagles at the Northern Sea of Okhotsk: What Did We Learn?
Abstract
For the past 27 years we have monitored the numbers and breeding output of one of the undisputed endemics of the Russian Federation, Steller’s Sea Eagles (Haliaeetus pelagicus) along the coast and major rivers of the Magadan District, North East Siberia, Russia. Every year we checked at least 40 territories in constant ‘model’ study areas located near Magadan, amassing data from 600 potential breeding attempts. The number of chicks fledged per successful pair has declined over the past 10 years, and has started to decline in a few localities on the coast. The declining breeding rate of Steller’s Sea Eagles nesting on rivers is associated with the frequency and severity of spring floods, as well as presence of ice-free channels in early spring. In the past decade, overall snow deposits in river systems have increased, producing severe and lengthy floods. Such floods impede successful hunting by the eagles, which reduces breeding output. The the past few years the sea coast sub-population demonstrated a very low breeding output in the portion of the coast with little or no ice cover in spring. Since this portion of the Sea of Okhotsk remain ice free in the past few winters, some portion of the coast demonstrated zero breeding output in contrast to high breeding output with normal ice cover in winter. We present a statistical model that predicts the breeding output of Steller’s Sea Eagles based on snow accumulation prior to the breeding season for the riverine nests and on early spring sea-ice density for the coastal nests, and explain mechanism of formation of the changing ice and snow conditions based on the changes in climate.
