POPULATION NUMBERS, PHENOLOGY AND PRODUCTIVITY OF THE BLACK-LEGGED KITTIWAKE (RISSA TRIDACTYLA, CHARADRIIFORMES, LARIDAE) FROM TAUISKAYA BAY, SEA OF OKHOTSK

On the islands and coasts of Tauiskaya Bay, 13 colonies of the black-legged kittiwake are known to exist, totaling about 150 thousand individuals. Most of them (about 100 thousand individuals) inhabit Talan Island. In other parts of Tauiskaya Bay, their numbers in colonies are not high, while the largest of them are located on such islands as Umara, Shelikan and Tri Brata, as well as on Cape Skalistyi, Koni Peninsula. In all colonies, the numbers of birds have increased considerably since the mid-1990's and remain persistently high up to now. Long-term monitoring shows a considerable shift in the beginning of the nesting period on Talan Island since 1999, this concurring with a later destruction of the ice cover and a low temperature of Tauiskaya Bay's coastal waters. In 1988-1993, first eggs were found in kittiwake nests between 2-11 June, versus 14-27 June in 1999-2012 (except for 2007). In 2014, a tendency to an earlier nesting was observed. The onset of egg-laying averaged 13 June. In Odyan Bay, where Umara Island is located, egg-laying in some years started 7-10 day later than on Talan Island, this being related to a later removal of ice from its water surface. In 1988-2016, the reproductive success of kittiwake on Talan Island varied from 0 to 69% (average 33.90%), the hatching success from 3.1 to 85% (average 57.7%), the chick success from 0 to 86.2% (average 50.5%). The number of fledged per pair with eggs varied from 0 to 1.19 (average 0.52), the number of fledged per pair from 0 to 1.05 (average 0.41). On Umara Island, black-legged kittiwakes bred more successfully, this being related to more favorable environmental conditions and relatively stable food resources in Odyan Bay. Thus, in 1993-1997 and 2005 their reproductive success varied from 0.68 to 1.25 fledged per nest with eggs (average 1.01), while the productivity from 0.53 to 1.05 fledged per nest with pair (average 0.80). Slaty-backed gulls (Larus schistisagus) and crows (Corvus corax) most often utilized abandoned eggs and fledglings (alive or dead), this taking place in conditions of forage deficiency caused both by unfavorable weather conditions and resource deficit in the water area of Tuiskaya Bay. Steller's sea eagles (Haliaeetus pelagicus) were both direct and indirect predators on adult black-legged kittiwakes, their eggs and fledglings, but no noticeable damage from their activity was noticed on Talan Island. Since 2008, a decrease in black-legged kittiwake productivity was noted on Talan Island, expressed in a high percentage of non-breeding pairs, a reduced clutch size, an extremely low hatching success and the loss of all or almost all fledglings from hunger. In 2016, against the early and mass nesting of kittiwakes, the parameters of clutch size and breeding success appeared to be the highest for the latest years. This encourages optimism in a successful life of the populations in Tauiskaya Bay, namely, on Talan Island.