This post was written by Shannon Hackett and Chad Eliason, who study birds in the Integrative Research Center at The Field Museum.
Feathers are the first things that many people think of when they think of birds. Well, maybe flight is the first, but feathers enable flight. So, what are feathers and what do they do?
Where do feathers come from?
To start this off, we will point out that feathers are not exclusively a bird thing. It’s true. Over the last 20 years, we have seen instance after instance of feathered dinosaur fossils clearly showing that feathers existed before modern birds. They are amazing to see, and some of these creatures were truly remarkable. The science is now clear that birds are just living dinosaurs (or as we bird people might like to say, dinosaurs are extinct birds), so it shouldn’t necessarily surprise us that feathers can be found in the closest relatives of birds, the theropod dinosaurs. However, scientists now have evidence for feathers in even older lineages of dinosaurs, those not on the branch leading to modern birds. Feathers have been around for perhaps 150 million years.
Not only do we know that dinosaurs had feathers, we can use what we know about modern bird feathers to infer colors and patterns in these extinct dinosaurs. A study of a fossil of Chinese dinosaur with feathers, Anchiornis huxleyi, gives a new look at this dinosaur's amazing coloration and patterns.
Another study that prompted us to talk about feathers showcased a tiny new dinosaur fossil with a tail whose feathers are perfectly preserved in amber.
What is the true reason for feathers?
We think of feathers helping birds fly, or keeping birds warm, but maybe the display functions of feathers are really at their origin. Birds just want to have fun, dance, display—feathers are how birds really show their stuff, and it seems that the same was true for dinosaurs too.
So what are feathers, then?
Feathers are made up primarily of keratin, the same stuff that your hair is made of. A good analogy for feather structure is a tree. Like trees, feathers have a central "trunk" called a rachis and several "branches" called barbs. These barbs are covered in leaf-like structures called barbules. If you've ever run your fingers along a feather, it's these barbules that keep the barbs connected and that form an aerodynamic surface for flight. Unlike plants, feathers grow differently—the oldest parts of a feather are at the tip, not at the base like on a plant. Variation in the speed at which feathers grow and the shapes of the structural "building blocks" explain the diverse shapes and different functions of feathers, even within a single bird!
We will be talking more about plumages (all the feathers in a bird) and how birds produce colors in their feathers in future posts.