The dispersion of arctic breeding birds according to snow-free patch dimensions during the spring thaw in the north-eastern Taimyr Peninsula,Russia

 The dispersion of passerines, ptarmigan Lagopus mutus and waders in relation to available snow-free patches is described after spring arrival but prior to the main thaw at Pronchishcheva Lake, north-eastern Taimyr, in June 1991. The numbers of ptarmigan and passerines were proportional to patch perimeter but disproportionately more birds occurred on smaller patches. In contrast, wader numbers were proportional to patch area but disproportionately more occurred along the perimeters of large patches. These patterns are discussed in relation to risk of predation and food availability. We speculate that the predation risk is higher in small patches for uniformly coloured birds but may be lower for white and pied species. The availability of overwintering plants, fresh plant growth and insects is thought to be highest at the perimeters of snow-free patches. Received: 19 November 1993/Accepted: 4 September 1995