" I never saw a wild thing feel sorry for itself. A small bird will drop frozen dead from a bough. Without ever having felt sorry for itself."

This quote means that animals don't regret anything they decide to do. When it say a "wild thing" it means that the birddoesn't have a owner but lives in the wild. Also it state that it's frozen dead, which could be in a winter season and the bird couldn't take it anymore because it doesn't have anywhere warm to be in, so it doesn't felt sorry for itself even if it had to died.