THE ROCK PTARMIGAN (LAGOPUS MUTUS) IN THE CENTRAL VERKHOYANSK RIDGE

The rock ptarmigan, Lagopus mutus, is common for mountain regions of Yakutia. In the central part. of the Verkhoyansk Ridge, during the reproductive period, the lower boundary of this species is at an attitude of 650 m a.s.l. on the north-facing macroslope and at 800-850 m on the south-facing one; the upper limit is 1200 m a.s.l. The mean nesting population density amounted to 1.3 ind./km(2) and differed by 34 times from year to year. The number of Lagopus mutus was high in 1987-1988 and 2000-2001, i.e. within 12-13 years. In some years, the birds move for large distances. Thirty-eight plant species and 22 invertebrate ones were found to be items in the diet of the rock ptarmigan. In winter periods, a daily diet of the bird is 65.0 g of dry mass. The coupling of rock ptarmigans is observed since the third decade of May. The brooding period lasts 20-22 days, and hatching occurs in early July.