Parakeet has a swollen abdomen and no feathers in that area.

by Jane
(Watertown, WI USA)

I noticed tonight that my parakeet has a swollen abdomen - not chest, but lower forward from her "rectum" and there are no feathers in that area. It feels mostly soft, but a bit harder on the sides. She is behaving as usual although she eats all the time (again, as usual.)

She is caged with 2 other keets that I believe are males. She is about 4 years old and the most wonderful loving and social budgie. Any ideas? She has always been a big, healthy bird so although I always thought she was a bit chubby, this is a fairly recent thing (swelling) and I don't know if I need to panic!
Any advice would be helpful! Thanks,
Jane Rakos