My yard in the winter when I am the only one on the block who didn’t blow and bag all the leaves in the fall:
Every starving bird in the neighborhood comes to eat. No, I have no idea exactly what they’re eating. Probably something mentioned in this article from the Audubon Society:
https://www.audubon.org/news/to-help-birds-winter-go-easy-fall-yard-work
UPDATE: The above video was taken in early winter 2019, the first year I skipped fall cleanup. It’s now the end of January 2020 and my yard has been taken over by a flock of birds, mostly robins. Yes, robins. None of my neighbors have birds in their yard, but I have easily fifty birds out there. An online search (DuckDuckGo, every time!) led me to this awesome piece on robin migration, overwintering, winter diet, and flocking (including with other birds). It’s fascinating. It also suggests leaving the leaves and other yard growth over the winter as well as planting berry bushes and crabapple trees as things that benefit robins. Check this out: