Observations of Molt in Overwintering White-throated Sparrows

Only one of the multiple overwintering birds seen, but two others heard.
Hoping to be able to study these closer to find out if they are the same formative plumage birds that wintered here that have molted, or a new wave of adult migrants coming through.

One observed under feeders, resting in brush pile and scratching on ground. Appeared to be in, or perhaps has completed, prealternate molt from the formative plumage worn throughout its winter stay to first alternate plumage. Multiple WTSP were observed here recently with very scruffy-looking heads, and some of the body feathers of this bird appeared to be feathers retained from formative plumage, with worn/drab-looking wing coverts, weak buffy wingbars, and rectrices that did not appear super worn but not newly replaced either. This suggests that either only the head was molted, or that the head and a some of the body feathers were molted. The head stripes were crisp and bright, but became worn and brown towards the posterior of the white median crown stripe and the black lateral crown stripes. I wonder if the prealternate molt is not yet complete, or if these these remnants of the formative plumage will be retained throughout first alternate?
Most of these birds have been singing more lately, and though they look like mature adults in plumage, they obviously still have a lot to learn about their song!

Posted on 14 April, 2020 14:54 by wbarker26 wbarker26


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