We’ve had this question sent into us a few times, usually on the back of someone reading about whether birds have belly buttons.
Birds don’t have nipples, as they are not mammals. Although, we talk about birds’ breasts they don’t have mammary glands which mammals use to feed their young milk. Here the term breast is used to describe the pectoral muscles birds use for flight.
Some birds, such as pigeons and doves, do feed their young milk, which is a secretion from the lining of the crop, a muscular pouch that forms part of their digestive tract.
Crop milk is unlike mammalian milk. It is very high in protein and fat and is semi-solid with a structure similar to cottage cheese. Crop milk also contains anti-oxidants and immune boosting substances as well as antibodies and bacteria.