One of the most common and easiest birds to identify in the Northeast, our White-breasted Nuthatch is known for visiting bird-feeders, walking upside-down down trees, storing seeds away from the feeder, and it's peculiar yank call.
This yank makes the White-breasted Nuthatch one of the easiest birds to identify down to the subspecies level. eBird groups the eleven subspecies into three groupings: here, in Vermont, we have a single common species, the nominate Sitta carolinensis carolinensis. It alone of the subspecies emits this call. An example of this nasal, polyphonic call can be heard here.
However, beyond this one characteristic, identifying this bird to subspecies is a bit more difficult.
Birds of the World (Grubb and Pravosudov 2020) says:
Birds in the eastern United States and Canada utter a nasal yenk... Bill stout, blunt; ventrum white; dorsum pale blue-gray.
The dorsum is particularly marked compared to western subspecies, which are darker. It should be noted that dorsum color is also used to sex White-breasted Nuthatches, with pale-crowned birds generally being considered female. However, Wood (1993) shows that "determining the sex of birds in the field at a distance is considerably more difficult. East of the Great Plains, at least 10% of all females regardless of population have little enough gray in the crown to be easily mistaken for males." (This is much more difficult in the southern regions of their range, such as in Florida). This means that dorsum color should not be used as the only justification for subspecies identification.
Pyle (1997) writes:
Geographic variation: Weak to moderate and clinal were most ranges meet. ... Crown of female gray to partly (occasionally completely) dull black; back pale to medium brownish gray (male) or blue-gray (female); inner webs of the terts black; sides fo the breast and flanks white to grayish white with a brown tinge. ... Birds breeding north of NC-AR are larger, average paler overall, and have female averaging less black on the crowns than southern birds, but differences are broadly clinal.
Looking at his breakdown, the only really salient characteristic that can be used is brown in the sides and breasts, and a short or medium-short bill, indicates that a bird is carolinensis, aculeata or oberholsi. Coloration of the back is clinal and variable - generally, a bird with a pale back will be a carolinensis, but as females have a pale blue-gray back in every population, this isn't a great indicator. A female with a partly or completely dull black crown would also indicate carolinensis, but how would you tell this from a male? It'd be tough. Pale birds should also be left unidentified during juvenile season.
In short, this is a difficult bird to differentiate clearly by any specific marker in the field, excepting the vocalization. Aging or even sexing a White-breasted Nuthatch can be difficult in the field.
To date, there are no records of other subspecies in Vermont.
Nomenclature:
Local subspecies records:
Needs:
These needs reflect eBird's database, and whether the bird has photos, audio, or sightings in a given area. "None" denotes that this species has been satisfactorily documented.