Under very special preservation circumstances, feathers to fossilize. You can see some examples of dinosaur fossils in this Wikipedia article. If you search you can also find lots of bird feature fossils (avian dinosaurs).

https://en.wikipedia.org/wiki/Feathered_dinosaur

this article is from The NY Times and I am only linking to it because the first photo in that article is an amazing fossil of a feather. https://www.nytimes.com/2020/09/30/science/dinosaur-feather-...