I have a pair of cockatiels who just laid their 1st clutch. She laid her eggs in a cardboard box I have on the floor instead of the nesting box which was attached to her cage. Anway, at night, while the female is sitting on her eggs, I put my male in his cage to sleep. In the morning, they usually switch and my male will sit on them during the day. The problem comes around 6:00 or so in the evening. She wants to go sit on her eggs but he won’t let her. She’ll go into the box and it sounds like they’re fighting in there. I’ve actually seen him corner her and was trying to bite her. At this point, it takes some time but, I get him out of the nesting box and put him into his cage. Is this normal behavior for a male.