dandee

I have a pair og budgies that in the breeding box a pair of chicks. An cockatiel has moved in and laid her eggs to which she is sitting on. she appears to be protective of the two budgies to the point where she will not let the parent budgies back into the nesting box. she covers the two budgies protectively when I look into the nesting box. has anyone come across this before and what was the outcome?