Hi bird therians! I'd like to present the following list of definitions of avian terminology; instincts and anatomy. Specifically, terms for things that many birdkin may already be aware of due to their own shifts, but not know the word for or even that it's a real and normal thing. Why do I make that assumption? Because my own mind was blown every time I discovered one of these words, the way things I would do or phantom parts I would feel suddenly made sense. So I hope to induce the same reaction in at least someone.
Behaviors
Mantling is mostly a bird of prey thing, the action of leaning over a kill and shielding the spoils with your wings so as to defend it from thieves. I can do no better of a description than a photo, included at the bottom of this post and for raptors it will probably spark recognition.
Rousing is the word for that "slowly fluff up the feathers and then shake the whole body" thing that birds do. Yes, it does have a name! Birds do it when relaxed or just chilly. It is not a threat display. I experience this as like an near-involuntary action -- like scratching an itch or sneezing -- and because I'm not actually raising physical feathers it feels kind of like shivering. But it sort of feels frustrating that I can't seem to achieve it. Like when a sneeze goes away.
Feather-plucking (pterotillomania) is a maladaptive habit birds in captivity develop when they are stressed. You see it most often with parrots, because they're kept as pets more than other birds and are also extremely intelligent so more easily understimulated. Sometimes this does feel like being a bird in captivity and a lot of you might experience this instinct without knowing what it is your brain's asking to do because you have no feathers. Calling it pterotillomania is helpful to me because I have actual dermotillomania and if my body had feathers I'd be plucking them.
Anatomy
Nictitating membrane. Starting with this because you may already know it by now. The third eyelid of birds, translucent, drawn sideways across the eye so that you can keep it moist while still being able to see. Also, as you may know, relevant to cat therians!
Crop. Part of the digestive tract of a bird in the throat where food is temporarily stored before being digested. If you had these shifts it would feel like, according to Wikipedia, basically an enlarged portion of the esophagus.
Keel. An extension of the sternum, the structure to which flight muscles are attached. If you had these shifts it would feel like a thin bone going beneath (or I guess on a humanoid body plan, in front of) your ribcage.
Cloaca. In the interest of not having to mark this post mature, I will not define or describe this one. I encourage you to look it up. Mammals are already working to reduce the stigma surrounding these types of shifts and instincts; we can do the same. There is no shame in it. You're a bird and birds have these. Accept it.
Birds do have sensation in our beaks. There are nerve endings in the beak. Not as much as, say, human skin, but yes, birds can feel touch on their beaks. If you can feel your beak, great! That is anatomically correct, and it certainly does not make you fake!
And now for your enjoyment, a mantling eagle:
