Thank you for the detailed reply. It's hard to tell from just pictures but it doesn't look as if she scrape her head anywhere because, when that happens, the loss of feathers is right on top of the head and she has it more to the back. Now, you say that you never see them preening each other but the spot where the feathers are missing is a spot that is usually preened in allopreening. The cage is not really very good, you know? I don't mean to be critical but I am VERY picky when it comes to cages for my birds so I'll share my thoughts with you and you decide. I like that it's white ( think that light colored cages are less oppressive than dark ones) but it's too low to the ground. I like cages that are on a stand so the actual cage goes from a height of our waists all the way up to our heads - this way, their roosting perch is at our eye level which is the ideal height for them. Flighted birds find safety in height -it's their way of avoiding predators- so, when the highest point they can reach is lower than your sight, it makes you look as if you were looming over them when you stand next to the cage - and that is stressful to them. The other thing that I do not like at all is the little 'tower' thingie higher than the rest of the cage... Birds always go to the higher perches so these 'cathedral' towers only make the space where they live much smaller than what is needed because they hardly ever go down to the ground of the cage where the only roomy space is. Funny thing is, these cages are usually more expensive that then plain, square roof ones that are much more practical and better for the birds.
Now, I think that the problem is that she got her nape preened a bit too enthusiastically by her boyfriend and, because the diet is too high in protein, she might be going into a soft molt - this is when the constantly molt feathers - not necessarily in a noticeable manner in the sense that you usually do not see 'bald' spots but you do see them replacing feathers all the time, something that is abnormal because birds do not molt all the time. There are species of birds that molt more than once a year but parrots molt only once and this usually happens right after breeding season. When you feed too much protein, the body needs to find some way of getting rid of it and it starts by producing feathers all the time which damages the plumage. My Javi Caique came to me in soft molt and he had been on it for years and years to the point that his belly was not a nice, thick, even white - it looked grayish and this was because the feathers were so thin that you could kind of see the dark skin through them. He had been free-fed a parrot seed mix for years which is waaaayyyy too much protein for a caique that is supposed to eat A LOT of produce and low protein. He has gotten much better on the right diet (his belly is now a nice, solid white with thick and healthy plumage) but it has taken years...
As to the diet... well, Alexes are mainly fruit eaters so the diet you are giving is the wrong one. They should get no sunflowers seeds or pellets. They need a lot of produce (BIG fruit portions) on a daily basis and a dish of low protein, low fat, high fiber, high moisture like gloop, for example. Free-feeding high protein, as you are doing, will not only cause terrible molts and all kinds of plumage problems, it will also result in liver and/or kidney problems. People talked about the 'mojo' molt of the psittaculas and the ekkies for years as if it was a normal thing for them but it's not. It's nothing more than a symptom of a very bad diet and, if you look at pictures of mojo molts, you will see that what your Bella has looks exactly the same (see this picture:
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