Northern Rough-winged
Swallow

The leading edge of their outer flight feathers features microscopic hooks (in males) or pointed tips (in females) that feel rough to the touch. Scientists still debate what purpose these tiny serrations serve.

They do not dig their own long tunnels. Instead, they use pre-existing burrows abandoned by kingfishers, squirrels, or Bank Swallows.

Unlike most other swallows that form noisy, massive colonies, rough-wings prefer to nest alone or in very small, loose groups.