In highschool, we had an ornithologist that would set up birding nets to band songbirds, and stuff. Or biology teacher would always give him time if he got something interesting.

Anyhow, of particular memory, there was a black capped chickadee that the teacher wanted a good photo of- so the ornithologist held the bird by the legs (kind of like he was perched on the back of his hand?). The tiny thing immediately began hammer drilling his knuckles. Drew blood.

Another time, a cardinal took a hefty chunk out of the soft bits near his thumb. But, uh, it was the Canada geese he was afraid of….