I have asked for help twice on the starling discussion board with this issue and the first time, got one reply to the effect of "I dunno" and this time, no replies at all.
Ringo's tummy feathers hang down vertically instead of lying against her body. Now she's losing feathers to the point she has bald patches. She isn't plucking. They fall out. She lost all the feathers on her back when I had Benjy in her room, but those grew back. Now she's got a couple of those growing in odd directions, but no bald patches, at least.
Her energy level, poops, appetite and everything is perfectly normal for her. She's very bright-eyed and curious about everything. She talks and sings and plays as usual. She takes several baths a day and always has. Her preening is no different than usual. Her diet is what is generally recommended for captive starlings, a mixture of cat food, egg protein pellets, softbill pellets (just a little of that) and I give her blood worms and meal worms (freeze dried) as treats. Like the parrots, she's picky about fruits and veggies and usually won't eat any of those. I occasionally give her vitamin drops because it's winter and she isn't getting to catch any live bugs as she can in summer when moths and things get into her room. I don't use cleaning products on her cage, just water. As far as I can tell, there's nothing in her room -- and she doesn't leave her room, because I don't trust our dog Jack -- that could be an irritant. The bare skin I can see is the right color and is not inflamed or rashy.
Starlings having their first adult molt can take forever about doing it, as long as three months, and she was due for her first adult molt in about September. However, starlings molt the way any bird does. They lose feathers and get new ones without having bald patches. When she had her baby molt, that's the way it was. If she had pin feathers or signs of incoming growth on the bald places, I'd think she was just having an ugly first molt, which can happen. But I don't see signs of incoming growth.
Starlings are considered an invasive species and a pest in the U.S. and therefore not illegal to keep as pets. However, they're also unpopular in general and the vet I use for my parrots isn't a specialist in avian medicine. If I needed one of those, I'd have to drive an hour to the only exotic bird vet in Illinois, IF I could get an appointment, and he specializes in parrots, not starlings. I'm not sure he'd even agree to see a starling.
I'm tempted to take the other foods away -- the egg and the softbill pellets -- because when I only fed her cat food, she didn't have this problem. It may not be related, but it may be. I can't pinpoint exactly when I noticed this change in her feathers, but change in feather condition is often related to nutrition. The starling forum people insist that this mixture of foods is necessary for starling health in captivity, but she was weaned onto cat food and ate nothing else but cat food for several months until I came upon that forum.