This Chestnut-backed Chickadee is molting his head feathers, hence the odd colors.
After breeding, if you’re a bird, comes molting. Time to discard those old, worn, raggedy flight feathers and start with some fresh ones for the long haul of the fall molt, or replace sparse downy feathers with good warm ones for the cold of winter. This means that around now—from mid-July to September—you may see a lot of birds who aren’t looking their best.
As fledglings undergo their fall molt (the Prebasic I molt), their appearance changes from obvious-youngster to apparent-adult. In the middle of that transition, they look a little… wild. It’s a strange and fleeting look, here-today-and-gone-in-two-weeks. We’ve caught enough molting fledglings that I’ve been able to put together a series of photos showing the transition.
Fledgling juncos start out a streaky light brown, with dark bills and yellow gapes.
Young fledgling GRAS
As they get older, the yellow gape shrinks.
Older fledgling KALI. Note the remnant of yellow gape at the edge of the bill.
You know it’s the end of the breeding season when everyone starts molting.
ALGE molting his primaries and secondary coverts
Tough Little Birds 