Jasper is going through a lot right now! He's experiencing his spring molt a little early. When birds molt, they shed a significant portion of their feathers and grow new ones in. This allows them to have fresh feathers for the new year, which ensures efficient flight, weather resistance, and camouflage. When feathers first grow in, they are surrounded by a sheath of keratin, which gives them a spiky appearance. They are called pinfeathers for this reason. Once the feathers are fully grown, the keratin becomes brittle and flaky, so the birds are able to preen them to crack the sheath open and reveal their fresh new feather!
This can be a somewhat uncomfortable process as pinfeathers can be sore and sensitive. Birds also seem to get pretty itchy when they have a lot of pinfeathers. There's nothing we can do to rush the feather-growing process, either. During molting season, birds will bathe more often to soften their pinfeathers. Softer keratin sheaths means some relief from the itchiness, and any feathers ready to crack open are easier to preen when wet. Jasper had just gotten done with having a bath in this photo
I haven't really thought much about how feathers are formed. The logistics of it growing and then peeling off is quite a neat bit of evolutionary gymnastics. It's both quite straight forward but also somehow cumbersome.
It's a great example of evolution being not teleological.
I went looking for a diagram of the follicle to show how interesting that structure alone is, but this one goes above and beyond. The report it came from is pretty intriguing as well, as it looks into possible evolution of feather follicle and mammary glands being similar. It's a bit over my head though, but still very interesting.
The images in B show the follicle structure. There's some sort of hormonal signal IIRC that triggers growth of a new feather. Follicles can become damaged by injury, in which case feathers can't regrow. If this occurs over a large area, such as a burn, infection, or persistent plucking, flight can be compromised.
In E (a-d) you can see cross sections of the pin feather through various stages of development. The rachis is the shaft of the feather, that you would think of when you picture a quill pen. Everything branches off of there. Barbs come out first, and then those branch off into tinier barbules. The Barbules link together like velcro, and that forms the 2 vanes of the feathers. If you run your fingers through a feather against the grain, you will feel resistance and that sensation of pulling apart velcro (though not near that tight!) and that is the barbules separating. When birds groom, one of the things they are doing is setting those barbules back together nicely. This is what gives them a semi-rigid structure, so that when they flap, the air doesn't just pass right through.
Great write up. So complex yet so common. The topography of the development of these is great.
As a former teenager do wonder if the follicles can get infected, like a zit..
Thanks for the in depth info, love it!
Glad you liked it! I like when I get to look these up and learn more myself.
Look up "feather follicle cyst" if you want to see it impacted. The pictures are super gnarly. It looks more akin to an ingrown hair, but since a feather is so much thicker, they are a lot bigger and scary looking. A lot look like bad tumors from how big they can get, and they can bleed a lot, so it's not recommended for people with pet/poultry birds to treat them at home. It's very interesting, and I'm not typically very squeamish, but I don't like seeing things come out of someplace they're not supposed to! 🤢
Thanks again. The feather follicle cyst is indeed what I imagined, and not so fun. Let's say that I won't go into the poultry business anytime soon.
But the knowledge is pretty fun, though!
Yeah, the feather cyst is new to me.
Being egg bound is another crazy one. My brother's workplace started keeping chickens there and one was egg bound, where the egg wouldn't come out. They tried stuff like soaking it's rear in warm water and such and they were all arguing over who of them had to try sticking their fingers up there to free it, but I don't think they ever got it and it died. All this farming stuff is too glamourized these days. Everything I learn about just makes me nope out of there. 😅
I'm still waiting to get in to the animal rescue, but I don't think I'd be involved with that kind of stuff, at least not right away. I think there's certifications and stuff you need to get first before you're allowed to participate in actual medical treatment.