Montane Avian Biogeography in Southern California and Baja California

Abstract

Montane bird communities on isolated ranges in southern California and Baja California were analysed with respect to patterns of diversity and composition in tests of various island biogeography hypotheses. Low species/area slopes and small amount of geographic variation suggest that colonization is generally recurrent and frequent. The importance of barriers that separate the mountain islands from one another varied depending on residency status and habitat choice of the montane birds. Mid-elevation forest birds and permanent residents appeared to have a variable response to the intervening nonmontane barriers, whereas summer residents and birds of meadows and Subalpine Forests were not as affected by their insularity. These com- munity traits may have arisen in response to the extent and distribution of montane habitats in both 'continental' ranges and isolated mountain islands.