The dark-eyed junco.

I didn't have the presence of mind to grab the camera and take a picture of the globular gray bird with a white belly, perched on the deck railing just beyond the glass. Instead I scrambled for my glasses, and the bird flew away. But we remembered how it looked, and Meade figured out it was dark-eyed junco, and googling, I found lots of photos but what I liked best was this lovely illustration and story.

The junco was not so much flying in to the window as it was flying right up against it. It would fly up and down the window's length, using its claws to aid in climbing. All the while it peered at us. It did this repeatedly. Various hypotheses were tossed about as to why a junco was engaging in this risky, precious energy expending behavior....

Dark-eyed juncos are "the 'snowbirds' of the middle latitudes." Of the middle latitudes? That makes me look up "snowbird" in the OED. Snowbird... I just think of that cornball Anne Murray song. But the OED says a "snow-bird" is "One or other of various small European or American birds, esp. the snow-bunting (Plectrophanes nivalis), snow-finch (Montifringilla nivalis), or snow-sparrow (Junco hiemalis)":

1694  Philos. Trans. 1693 (Royal Soc.) 17 996   The Snow-bird which I take to be much the same with our Hedge Sparrow; this is so called because it seldom appears about Houses but against Snow or very cold Weather.

OED has this 3rd definition: "3. U.S. slang. One who sniffs cocaine (cf. snow n.1 5d); gen. a drug addict":

1923   J. F. Fishman Crucibles of Crime vi. 126   It was discovered that each of them [sc. handkerchiefs] has a small ink mark in one of the corners..these handkerchiefs had been dipped in cocaine... The mark in the corner notified the ‘snowbird’ that it was ‘loaded.’

There's a 4th definition, also U.S. slang:

1923   Nation 31 Oct. 487   In winter, when building is at a standstill in the North, northern workmen, ‘snow birds’ or ‘white doves’ in Negro parlance, flock south.

And a 5th definition: "A person who likes snow; a snow-sports enthusiast." And here we get a D.H. Lawrence quote from 1928: "I am no snow-bird, I hate the stark and shroudy whitemen, white and black." [ADDED: Is "whitemen" an error in the OED?!] That's from something called "Not I," which I can't seem to find on the web. But with some "snow-bird" searching, I did come up with this D.H. Lawrence poem, "Self-Pity":

I never saw a wild thing
sorry for itself.
A small bird will drop frozen dead from a bough
without ever having felt sorry for itself.

You're not feeling sorry for yourself on Christmas Eve, are you?