Range Extension of the Blue Jay into Western North America
The Blue Jay (Cyanocittcar istata) is a common permanent resident or migratory summer resident in the eastern half of North America (reviewed by Wenger, 1975). Few extralimital winter records of Blue Jays existed in western North America prior to 1972. Since then, western sightings have been increasing annually with over 220 records in the winter of 1976-77. Because Blue Jays are usually conspicuous, easily identified, and often remain in localized urban areas for several weeks, these reports reflect a genuine increase and suggest that the Blue Jay is rapidly expanding its wintering range. Recent records also indicate a westward expansion of the breeding range. This report reviews the recent changes in the Blue Jay's distribution and offers explanations for two important questions concerning this expansion: (1) what factors are influencing this westward expansion, and (2) where is the origin of these pioneering individuals?
Smith, K.G. (1978). Range extension of the blue jay into western North America. Bird-Banding, 49(3): 208-214.