Biogeography of white-tailed ptarmigan (Lagopus leucurus): implications from an introduced population in the Sierra Nevada

Lagopus leucurus is a primary alpine species that was historically absent in the Sierra Nevada until 72 birds were introduced in 1971-72 from the Rocky Mountains, Colorado. Currently, the Sierra Nevadan alpine is suitable for ptarmigan survival as determined by the breeding success of the introduced population, yet deep spring snowpack negatively affects breeding success. If Pleistocene snows were consistently heavier in the Sierra Nevada than today, establishment of a population of ptarmigan may not have been successful. In the Holocene, temperatures, exceeding present conditions in the Sierra Nevada may have subjected the birds to critical heat stress since the species is intolerant of high temperatures. Thus, the Sierra Nevada may have been unsuitable for ptarmigan survival in the past in addition to being inaccessible. -from Authors