Common loons experience a full body molt starting in late summer/early
fall. By December, most loons have fully molted into their gray winter
plumage.

I didn't look at your photos, but I suspect the bird in question is in
the process of completing its molt.

The eyes of adult loons remain red year-round.

For more info and some great photos by Washington photographers Ginger
Gumm and Daniel Poleschook, see "Call of the Loon" by D. Evers and K.
Taylor, 2006.

Russ

--------------------------------------------
Russell Link
District Wildlife Biologist
Dept. of Fish and Wildlife
16018 Mill Creek Blvd.
Mill Creek, WA 98012

(425) 775-1311 ext. 110
linkrel at dfw.wa.gov
http://wdfw.wa.gov