Birds develop feathers the same way we develop hair and teeth

The hexagonal patterning of bird feather growth relies the same signaling pathway used to form hair, teeth, and scales in mammals, fish, and reptiles.

Getting to the root of scales, feather and hair: As deep as odontodes? - Dhouailly - 2019 - Experimental Dermatology - Wiley Online Library

Scales, Feathers and Hair Have a Common Ancestor - The New York Times

Finally, You Can See Dinosaurs in All Their Feathered Glory

How do birds move their feathers?

30 Extraordinarily Beautiful Birds You Might Not Have Heard About

Human hair, bird feathers came from reptile scales, Science

How we finally figured out the color of dinosaur feathers

Do any birds have hair instead of feathers? If so, why? - Quora

Everything You Need To Know About Feathers

IBP - Blog Post

Glossary of bird terms - Wikipedia

Caudipteryx, Early Cretaceous, Feathers, Flightless

As light as a feather