Hi Eva,
Since you mentioned the cere is turning brown, I assume these are budgies/parakeets. She is using the food bowl as a nest, so it’s best to take that away from her and replace it with some smaller cups she can’t sit in. Otherwise she is going to end up laying eggs. Birds do not carry eggs inside them. Each egg is formed in 48 hours, and then she lays the egg. She is getting less friendly because she has a mate and she wants to breed. Breeding birds do not want to be touched or handled. So if you do not want to breed them and lose them as pets, you need to take the bowl away and discourage nesting. You can limit their light to 8-10 hours by covering the cage early each evening. Move the cage to a different spot in the room at least once a week, and rearrange the toys. When you do handle her, only touch her head – do not pet her on the body because this triggers her hormones. Do not give her paper or cardboard to chew on. Don’t let her sit on the cage floor or use anything as a nest. If you do want them to breed – and keeping in mind they will not remain tame – then you need to research breeding and then get them a nest box.
Thank you for asking Lafeber,
Brenda