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.
Tough Little Birds 