Jerry Friedman

Despite what you just said, I believe it goes like this (subject to correction): HY: Hatched in 2020. (No one is so literal-minded that they won't understand how to apply this definition next year.) AHY: Hatched in 2019 or earlier. Birds become AHY on Jan. 1, sort of like racehorses. Juvenile: In its first set of real feathers (not all down). Immature: At least one non-juvenile feather has come in, but the bird is not in full adult plumage yet. Some birds have a few years of immature plumages. Adult: In a plumage that will be repeated more or less exactly next year (if the bird survives).

I think of "breeding plumage" as the one that they recognize and are attracted to for mating, and I have the impression that's a common way to think of it.

Just for practice until an expert comes along: With the heavily marked body and apparently all-dark head, it looks like the expected Western (calurus) to me. The dark tips of the feathers on the trailing edge of the wing make it an adult. Right?

Are Matt Young and Tim Spahr still identifying call types of recordings you upload to eBird, if you send them a checklist? https://ebird.org/news/crossbills-of-north-america-species-and-red-crossbill-call-types/

I think a brown redstart would probably be an adult male with aberrant plumage. I'm no expert on redstarts, but I suspect that in the transition from gray to black, they just lose gray feathers and replace them with black ones. American Redstarts are show-offs and often fan their tails--to flush insects, I guess, not really to show off. Was your bird doing that? Speaking of not being an expert, I'd guess that if you take some walks in the local woods around now, you have a good chance of seeing them. The eastern birders here will know more.

Not an expert, but I don't see any reason to doubt Eastern. Northern (abieticola) would have heavy facial marks "dripping" down onto the breast and a heavy, blobby belly band, wouldn't it?

Welcome to Whatbird! Maybe a Bobolink?

American Redstart, maybe a male with faded or dilute plumage?

They'll be notified that The Bird Nuts tagged them, so they'll probably look at this thread.

Am I mistaken, or is 3 literally semipalmated, with partially webbed toes? Can Least ever be like that?

OK, thanks.

Also the big beak whose top edge continues the line of the forehead, flat-topped head, "mean" expression, dark brown streaks, hefty legs, and tail with the inner feathers shorter than the outer one.

Violet-green has white up behind the eye. That looks like a Tree Swallow to me.

Tony Leukering's an expert who's written an article on identifying scaup (which I can't find the link to right now), and he's sure, so you can go with his answer.

If you know what kind of bird it is before you post, you can also post in the Photo Sharing forum, wid or widout a pun.