We usually see American robins (Turdus migratorius) with their wings closed. They perch in a tree, sit on a nest, or walk with their classic 3-steps-and-stop gait. Even in flight robins close their wings, flapping and gliding in a pattern similar to their walk.

This view of a robin with open wings reveals a surprise. The robin’s armpits, called axillaries, match its belly.

Check out this vintage article on axillaries to see other birds with hidden surprises.

(photo from Wikimedia Commons; click on the caption to see the original)