Winter feeding of ptarmigan (Lacopus lacopus, Galliformes, Tetraonidae) in Yakutia

Resumo

This paper presents the results of long-term studies on winter feeding of ptarmigan in Yakutia. This territory of the species habitat is characterized by the longest snow period and low ambient temperatures. Like in the predominant part of the range, the basis of winter feeding of birds is made up here of the vegetative parts of willow and birch. The period of winter feeding lasts 230–250 days in individuals of the northern populations and 170–180 days in individuals of the southern population. It was found that the preference for birch by ptarmigan changed to a preference for willow with advancement to the north and to the mountains. In addition to birch and willow, the diet of the birds includes up to 23 plant species. Among them, horsetail, chosenia, and larch can serve as the main food due to both biotic factors (the presence of animal excavations) and abiotic factors (thin snow cover, long-term severe frosts). In severe frosts, ptarmigans mainly feed on the ground using almost all the plants including those they do not prefer in warmer days. Two peaks of the craw fullness were observed in birds at average daily air temperatures below–50°C, and four peaks were noted in warmer days. The first peak is obviously due to the need to be in shelter for most of the daytime.