Breeding habitat selection of sympatric White-tailed, Rock and Willow Ptarmigan in the southern Yukon Territory, Canada

Abstract

We examined breeding habitat selection at two scales for White-tailed (Lagopus leucura), Rock (L. muta), and Willow Ptarmigan (L. lagopus) at an alpine site in the Ruby Range Mountains of the Yukon Territory, Canada. To infer species-specific preferences, we used logistic regres- sion and AIC model selection to compare nest habitat of White-tailed (n = 43) and Rock Ptarmigan (n = 58). Only descriptive statistics were used for Willow Ptarmigan (n = 8 nests) because of smaller sample sizes. Modeling results indicate elevation, slope, and the ground cover of graminoids and lichens were the main variables separating White-tailed and Rock Ptarmigan breeding habitat. Average estimates for elevation and slope around nest sites of each species followed a pattern of White-tailed Ptarmigan (1,827 m, 30) ( Rock Ptarmigan (1,728 m, 18) ( Wil- low Ptarmigan (1,512 m, 6). White-tailed Ptarmigan tended to select drier habitats dominated by lichens, rock and dwarf shrubs, while Rock Ptarmigan were more com- mon in meadows with graminoids and scattered woody shrubs. Willow Ptarmigan nested in areas with dense, woody shrubs. The three species display inter- and intraspecific territoriality, and while species-specific habitat preferences allow co-existence, the niche width of each is likely nar- rowed by the presence of congeners, particularly for White- tailed and Rock Ptarmigan. Within territories, all three species selected nest sites with more lateral cover than expected at random (24-50%). White-tailed and Rock Ptarmigan did not select specific cover types (vegetation or rock) for nest sites within territories, while most Willow Ptarmigan nests were located in patches of scrub birch (Betula glandulosa).