First, the male I guess, smaller one, of my favorite eastern cottontail pair was laying on his side this a.m. already stiff, with his neck turned back. I couldn't see any talon marks or something. He was about 3.5 feet from a bush ... could it have been a snake that struck him> What happened to him? It killed him but didn't eat him, just left him there? SO sad. Second, my nieghbor said her bluebird was laying on the ground outside of the nesting box. She cleaned the box out this year, and everything. I looked up an old book that said males and females fight sometimes over mates ... but not to the death right? Also the book said about larvae and flys that can kill in nest boxes and tree holes? What likely happened to this bird?

Without testing, it is hard to guess what killed the rabbit and the bluebird. Collision with a vehicle, attacked by a dog or cat or a wild predator, disease, age...there are any number of possible causes.