I have 9 button quail and every one is missing their lower back and tail feathers, male and female. What could be up?
They can pluck each others lower backs, especially when stressed. I have a male who will start plucking his babies when they start to get their feathers around a week old. Other than the plucking he is a devoted father and he never touches his mate. They can be strange little birds! They really do best as one pair per enclosure and they need a lot more space than coturnix - at least 5 sq ft per pair. So it may be a case of them feeling overcrowded and stressed by having to share their space with so many others.
They are in a 40 gallon tank. It seemed big enough. The guy I got them from keeps them in colonies in wire cages. I'll rethink the housing. Here's the enclosure but it's less green now. I'll get a pic of the backs tomorrow.
Feather picking can be a very annoying issue - once they've started, even if you correct what caused it (over crowding, keeping too many birds together and too little protein in the feed are common suspects) the problem might persist. Best case scenario - it's only two of your birds that are doing it to the rest. It has to be at least two since they all miss feathers - if one still had his, he would most likely be the one doing it to the others. If you can spend a few hours looking at them, you might be able to catch the culprits and separate them from the others. Keep in mind the behavior might be permanent, when you decide what to do about them. And then, as JaeG said - separate the rest in pairs. You might be able to get away with a trio if you end up with an unequal number once you've found the peckers. Looks like your colors are not going to be easy to sex though, so it'll probably be a challenge. If any of them seem to stay near each other a lot, they might be a pair.
Do they have a sand bath? They may have mites. Quail use sand to bathe in to keep the mites in check. The sand smothers the mites and they die. If you don't have a sand bath, I would get one. You don't need much. Even a box with low enough sides for them to get into will work. I'd get the sand at Petsmart by Nature's Choice, as it is made without silica, or find a sand without silica like kids sandbox sand. Set a couple in there and let them explore it and they will naturally figure it out. Usually one will, and the others follow suit.
What are the dimensions of this 40 gallon tank? The 40 gallon tanks I am finding online are all close to 3 feet by 1 foot or a inch or two more. That seems kinda small doesn't it?