Date: 10/28/19 9:35 pm From: David Tønnessen <davidtonnessenx...> Subject: [cobirds] Re: Possible Yellow-billed Loon, Cherry Creek State Park
Echoing what Nick said, I would've expected a paler loon overall with a heftier bill rather than what looks like stark contrast between dark upper parts and pale below, features typical of Common Loon. While not entirely invalid, bill color isn't something I find especially helpful for ID of the two species in basic plumage at a distance, especially as I've seen Commons with yellow-looking bills whether as a result of lighting or just general variability. A combination of hefty bill and overall structure, stronger scale pattern in the back, and overall pale and low-contrast plumage from the top/back of the neck to the underparts I find to be most helpful in picking out Yellow-billed.
Good Birding! David Tonnessen Colorado Springs, CO