You've gotten all the advice you need above, so all I want to say is please make sure that if your birds, any of them, have any type of "Happy/Snuggle Huts", tents, hammocks, any type of boxes (nest-boxes, wooden boxes, cardboard boxes), towels, blankets, any type of "bedding" material such as wood chips, shredded paper, newspapers they can get underneath, or anything else that could be considered a "nest" or "nesting material", it all needs to be removed from their cages/play areas immediately, and they should never have access to any of this stuff ever again.
All of this stuff causes their sex-hormones to go crazy and will cause the sexual behavior your Quaker is displaying, along with the aggression/biting. And this includes not letting your birds ever get underneath any furniture, inside of cabinets, etc. No "small, dark places"...And as for the "Snuggle/Happy/Cuddle Huts, the fuzzy tents you buy for birds that hang inside of their cages and that are usually yellow, purple, or green, they are not only bad for their hormones, but they have caused the sudden deaths of thousands of pet birds, so that's actually the more important reason you need to remove them if you have them... Birds pick at the material bit-by-bit, little-by-little over time, and it's totally non-digestible...So little tiny bits of it build-up inside of their Crops, their Stomachs, and their Intestines, until one day it's forms a complete blockage and the bird dies quite quickly...The other way they kill birds is they are full of threads that are inside of the material, and little strings let-loose and they end-up getting themselves wrapped-up in the loose, hanging threads...Most end-up hanging themselves with the threads around their necks, and a lot have also gotten the threads wrapped around their legs/feet, and then they end-up hanging by their leg/foot all day long until someone comes home and finds them...And many end-up chewing through their legs/feet and bleed to death...They're terrible things that shouldn't be sold. So if you or anyone you know has one of them for their birds, please warn them and tell them to remove them and pitch them...