A female pigeon is called a Hen.
Female pigeons who are less than a year old are Young Hens, female pigeons over one-year-old are Old Hens.
Female pigeons are very easy to confuse with male pigeons as they are the same size.
Another reason why it is difficult to distinguish between the two sexes is that male pigeons also help incubate eggs, sharing the job with their partner.
If you do manage to work out that a certain pigeon is female, you now know that the correct name for her is Hen not “girl pigeon” or similar!