Super interesting and another thing that makes me go HMMMMM... This study says that birds preen glands have a certain bacteria that produces their individual smell which they use to identify other birds and for procreation. My HMMM comes from wondering if the disruption of this bacteria (people who bathe their birds in warm water, use a blow dryer, touch their birds on their backs with hands that have lotion, perfume, etc or even giving them antibiotics on a regular basis -like breeders tend to do) has anything to do with the reluctance of some birds to even recognize other birds as birds and, of course, mate with them.
https://www.sciencedaily.com/releases/2 ... 103302.htm