Female birds are generally referred to as hens, although this term is often specific to species like chickens. For most other birds, the female is simply called a female bird or the species name (e.g., female sparrow, female eagle). Some species have specific terms for males and females, such as:
Doe for female deer-like birds (e.g., female pheasant)
Queen for some bird species like the queen bee-eater
But in most cases, the general term “female” applies to birds.
