Breeding Biology of the Parakeet Auklet (Cyclorrhynchus psittacula) on Talan Island (Northern Sea of Okhotsk)

Аннотация

The breeding biology of the parakeet auklet was studied in 1989–2012 on Talan Island, which is located in Tauiskaya Bay in the Sea of Okhotsk. In 2008, its population amounted to 3000–4000 individuals, and 70% of the birds nested on the western slope. In 2008, the average density of nesting on this part of the island was 0.018 pairs/m². Most of nests were noted along the slope base (5–20 m a.s.l.), while the largest density in these sites was 0.035 pairs/m². The time of egg laying varied from June 4 to June 14, and the longterm average annual date fell on June 8. The latest date of egg laying (June 12–14) was observed in 1995, 1999, and 2001, which was due to the time of ice crushing nearby the island. Hatching in different years started on July 9–19 and ended in late July–early August. The weight of hatchlings was 20–33 g (on average, 27.9 g). In different years, the maximum weight of 22-to 29-day-old nestlings was 173–263 g. By the time of fledging, their weight had decreased to 168–252 g, while the daily increase in weight for the periods of chicks staying in the nests was 4.06–6.47 g in different years. Young birds left the island in the period from the middle of August to the first ten-day period of September; the average age of fledglings was 31–35 days in different years. The reproductive success of the parakeet auklet varied from 0 to 83.3% (on average, 44.3%) and was mainly determined by the survival of chicks at different stages of their development. The main limiting factor of the reproductive success is the reduction of forage availability and abundance, which is largely due to unfavorable weather conditions (long cyclones with storm winds), as well as various hydrobiological changes in the environment. The influence of anxiety and predation was not significant with respect to adult birds, but these factors can cause death of clutches and chicks, and, being combined with unfavorable weather conditions, their effect increases.