Tuesday, January 17, 2012

Black-capped vs Carolina Chickadees

I am glad that we Minnesotans have Iowa, Wisconsin and northern Illinois separating us from Carolina Chickadees, the bird in the upper photo. Telling the two species is very difficult. Several subtle field marks exist. The first is the sharp demarkation between the black throat and the white breast in the Carolina and the Black-cap's more ragged throat line. This difference is obvious when you compare the Carolina Chickadee above (from northern Florida) and the Black-capped Chickadee in the next photo (taken in New York). Be warned that this mark is of less use in Carolinas with warn fall plumage.

The Black-capped Chickadee's wing coverts and primary edges tend to be white, whereas these feathers in Carolina Chickadees tend to be uniformly gray. You can see these pale edges on the Black-capped Chickadee that I published in a recent post from the Carleton College Arboretum. Again worn Black-capped plumages will give the unwary trouble. Two more field marks, less reliable than others, are that Black-capped Chickadees tend to have rustier flanks and whiter napes. These marks are (sort of) visible in the first two photographs. Black-capped Chickadees tend to be larger than Carolinas, but the size overlaps.
Finally, the two chickadees have different calls. The trouble is that, in the areas of overlap across the central United States, the two species learn each other's songs. To further confound identification, these chickadees also hybridize, blending characteristics. I think convincing the Minnesota rare bird committee that you have seen a Carolina Chickadee in our state would be a difficult task.

No comments:

Post a Comment