What was this thing on a crow

I watched this crow for about 15 minutes. It had the thing dangling from its chest. The bird was hoping around and eating apparently fine. The “bag” was free swinging.

When I moved closer for a better pic, it flew away. It seemed to otherwise ok.

Birds have a bunch of air sacs that allow for unidirectional flow of air through the gas-exchanging lungs. I wonder if it is possible for one to herniate outside the body.

Perhaps a tumor?

Could be a tumor, or a Christmas ornament. Animals get caught in all kinds of stuff from humans and just go on with life, as long as the thing does not debilitate them. People have a lot of Christmas decorations in their yards right now, so it’s possible. Hopefully, if it is something like that it will fall off eventually.

I guess that’s the better of the two, assuming he can ditch it soon enough.

Can tumors be bulbous but hanging on by a thread?

I used to put radio transmitters on American Crows Corvus brachyrhynchos to follow their movements. We always used cotton shoelaces to attach the radios such that they fell off after a period of time. But I don’t see an antennae nor any other indication that the crow was marked (no bands, bleached feather patterns, fake feather attachment), so perhaps this one got into a bit of trash?

I have seen large tumors on mobile birds that are quite impressive (one tumor on a House Sparrow’s Passer domesticus neck was the size of his head, but he had no apparent issues with it that I could discern. But I do think a herniated airsac of that size would impact the flight capability of a bird.

Christmas ornament seems more likely. And probably not harmful
Crows are known to be attracted to shiny things, like magpies (another branch of the crow family).

See: pedunculated.