Long-Term Trends of Chickadee Populations in Western North America

Abstract

We evaluated population trends of Black-capped (Parus atricapillus), Chestnut-backed (P. rufescens) and Mountain (P. gambeli) chickadees in the Pacific Northwest of North America using 41 years (1944-1985) of data from Christmas Bird Counts. Most (76-83%) locations showed no significant trends (long-term increases or decreases in numbers of chickadees detected per observer hours) for any of the three species. Five to 14% of the locations had significant declines and 10 to 13% had significant increases. The recent range expansion by Chestnut-backed Chickadees in the Sierra Nevada of California was not accompanied by declines in Mountain Chickadee numbers. Chestnut-backed Chickadee populations no longer appear to be increasing in the Sierra Nevada; however, some populations in the San Francisco Bay region of California are apparently still increasing.