Influence of the Vegetation Structure on the Numbers of Great Snipes (Gallinago media) (Scolopacidae, Aves) at Leks

Resumo

Abstract—The numbers of birds and vegetation structure were analyzed at 13, 7 and 10 leks of great snipes (Gallinago media), which formed at agricultural lands of Moscow Region in 2014–2016, respectively. Not less than 120–130 birds were concentrated on the leks annually, of which 82–94% were males. The numbers of great snipes changed asynchronously at different leks during the breeding season. It depended on neither the lek location (floodplain or watershed) nor the soil penetrability therein. A negative correlation was found between the bird numbers and the height of vegetation (n = 42; R_s = –0.52; p < 0.01) and between the bird numbers and the coverage of vegetation (n = 44; R_s = –0.56; p < 0.01) at the leks during the entire breeding season. Poisson regression has revealed a negative impact (p = 0.0162) of the average grass height on the bird numbers on the leks during the main period of activity of great snipes (May and the first decade of June). However, such relationships were not traced so clear by analyses of the movements of two marked males. A negative correlation between the bird numbers and the variance of grass height (n = 42; R_s = –0.48; p < 0.01) and a positive one between the bird numbers and the variance of grass cover (n = 44; R_s = 0.40; p < 0.01) were found for the entire breeding period (May–June). The numbers of great snipes were found to be positively correlated with the abundance of the lowest vegetation class (10 cm and below) during the entire breeding period (n = 42; R_s = 0.51; p < 0.01) as well as during the period of maximal activity of great snipes (n = 30; R_s = 0.41; p < 0.05). A conclusion was made that the heterogeneity of the projective grass coverage and the presence of fairly large patches with the lowest vegetation rather than the grass height itself are of importance for great snipes when selecting sites for lekking.