Spring‐summer movements of male capercaillie Tetrao urogallus: A test of the ‘landscape mosaic’ hypothesis

Abstract

The ‘landscape mosaic’ hypothesis predicts that adult male capercaillie Tetrao urogallus track available habitat when making distinct seasonal migrations. We tested this hypothesis by comparing movement from leks to summer range in three geographical regions, viz. northwest Russia (Pechora), southwest Russia (Tver) and southeast Norway (Varaldskogen). All radio‐collared males dispersed out of their daytime lek territories to an average distance of 2.3 km (±0.37) from lek centres (N = 52). In Russia, three birds, which were not included in this estimate, moved beyond the 6–7 km detection distance, but returned the following year. Due to large variation among birds at each lek, the only significant difference in movement was found between the birds at the lek in Pechora ( = 1.3 km) and those at one of the two leks in Tver ( = 3.6 km) and at one of the three leks in Norway ( = 3.2 km). At all leks except the one in Tver, the amount of suitable summer habitat, e.g. old Norway spruce Picea abies forest on rich soil, was smaller within a 1–km radius of leks centres than in the outer two 1–km zones. Despite a large proportion of old spruce forest at and near the lek site in Tver, the males at this site moved >2 km from the lek centre in late May/early June. When data were pooled, the dispersal distance did not correlate with the amount of old spruce forest nor with the size of patches (e.g. grain size) with increasing distance from leks. However, at the Norwegian study area, which is highly fragmented with a fine‐grained habitat mosaic due to commercial forestry, variation in topography and soil quality, birds tended to move farther away from the leks with increasing patch size and with increasing proportion of old spruce forest. When fitting a second polynomial regression function to the pooled data, there was only a weak relationship between dispersal distance and grain size for leks (P = 0.19). When including all birds, the relationship was highly significant (P = 0.002). The Pechora lek in northwest Russia contributed mainly to the lack of a clear relationship between movement pattern and distribution of old spruce forest. Here large, contiguous bands of old spruce forest were located along the main river courses in a coarse‐grained fashion within 2 km of lek sites. Thus, local configuration of preferred summer habitat at the landscape scale probably affects both direction and movement to a larger extent than predicted from the ‘landscape mosaic’ hypothesis.