Does anyone have Pyles at hand? I’m curious because the juncos I’ve been seeing in my backyard (Oregon Group) are becoming more vibrant in color and I’m wondering if they have molted and therefore identifiable past subspecies Group if a good quality photo is taken.
From the Birds of North America (summarized):
The main molt happens in fall and early winter (Sept-Dec). Some individuals molt a few body feathers (especially around the head) in Feb-Apr, but this is rare.
Juncos are alternate strategists, so all individuals should molt twice a year, once in the fall and once in early spring. The prealternate molt (spring) is limited to mostly the head, which does become a bit less dull in alternate plumage, compared to basic.
Males juncos are more “vibrant” in color than female juncos. That could be a factor in your observation.