Lu X. & Zheng G. (2007) Dominance-dependent microroost use in flock-living Tibetan Eared-pheasants. ARDEA 95 (2): 225-234

The Tibetan Eared-pheasant Crossoptilon harmani is a high-altitude galliform endemic to south Tibet. At a macrohabitat scale, we have shown that populations of this species are limited by a lack of suitable roosts in their scrub-covered montane habitats. To understand how the limitation may be linked to individual social dominance within a roost, this study investigated a single flock associated with a communal roost from winter to the breeding season. During winter, most birds clumped in a few trees sheltered by cliffs, but subordinate members of the flock roosted more often alone in marginal trees where higher thermoregulation costs and predation risks were expected. As soon as pair bonds established, breeding males behaved exclusively so that no two pairs shared the same tree, causing increased demands for roosting sites. Higher-ranking adult males still roosted in the trees preferred in winter whereas lower-ranking males were forced to use trees located marginally. As this bird population suffered no food shortage and experienced a low diurnal predation, we argue that the spatial segregation by social status potentially resulted in a density-dependent mortality that could be mainly responsible for a high mortality (48%) of the flock members over the study period. This provides additional evidence supporting the hypothesis that roost size is a crucial limiting factor of the Tibetan Eared-pheasant population.