posted March 22nd, 2011; last edited March 22nd, 2011 –– David Sibley

Chestnut-backed Chickadee Poecile rufescens

Geographic Variation

Northern Chestnut-backed Chickadee – Poecile rufescens rufescens

California Chestnut-backed Chickadee – Poecile rufescens barlowi group

Variation is distinct, with two groups involving mainly flank color (rich chestnut in the north, pale grayish on central California coast), but these appear to intergrade broadly in coastal northern California. No detailed study of vocalizations has been made.

Northern vs. California

  • flanks rich chestnut (vs. gray)
  • back slightly darker chestnut (vs. slightly paler and more orange-tinged)
  • white edges/tips on greater coverts average more obvious
  • white cheeks brighter and cleaner white to rear edge (vs blending to faint pale grayish at rear edge)

In California the birds from Monterey and southwards are pale and gray-flanked; San Francisco Bay area birds are intermediate with some rufous on flanks. To the north there may be gradual intergradation through at least Mendocino and Humboldt counties, where birds are mostly chestnut-flanked but seem not quite as bright as in British Columbia. Some inland portions of the species’ range, including the Sierra Nevada in California, has recently been colonized by Northern (chestnut-flanked) birds.

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