Feathers tell us all sorts of things about birds. They are beautiful to look at, help us identify individual bird species, protect birds from the elements, and they’re the reason birds can take flight. Ornithologists can tell us even more about birds thanks to feather measurements and samples. Some research labs even can measure where the carbon in feathers comes from, which tells us a lot about avian diets and migration patterns. However, before we get too deep down the rabbit hole regarding ornithological research, it’s important to start at the beginning. What are feathers, and how many types of feathers are there? To answer these questions, I consulted the Cornell Lab of Ornithology’s Handbook of Bird Biology from 2016.