Grinnell noted that the main differences between the boreal chickadee and the chestnut-backed were in the shade and tone of their respective brown coloration.

He drew parallels between the varied chickadee characteristics using the fact that some bird species become smaller and more vibrantly brown as their habitat becomes more humid.

[6] It is found in the Pacific Northwest of the United States and western Canada, from southeastern Alaska to southwestern California.

It is a permanent resident within its range, with some seasonal movements as feeding flocks move short distances in search of food.

[2] In fact, the abundance of Douglas fir trees can be a helpful indicator for the population of chestnut-backed chickadees in the region.

[6] In the San Francisco Bay Area, this bird has readily adapted to suburban settings, prompting expansion farther inland.

[10] Chestnut-backed chickadees feed largely on insects and other invertebrates gleaned from foliage (especially from that of the Douglas fir).

They often move through the forest in mixed feeding flocks, and can be spotted in large groups with bushtits, warblers, red-breasted nuthatches, and kinglets.