How do pigeons feed their baby milk?

Answer 1

Pigeons are birds, and birds do not provide the same sort of milk for their young as mammals do. Some birds are fed on special secretions from the parent birds' crop, and these may even be called crop milk, but it is not milk in the true "mammalian" sense of the word. It is not produced in mammary glands.

The production of the milk is controlled by prolactin, which is the same hormone that begins milk production in mammals, and is released from the pituitary gland. The lining of the crop sloughs off fluid-filled cells containing more fat and protein than cows' milk, as well as minerals and antibodies, forming a nutritious milk-like substance known as crop milk. Both males and females produce this liquid.

Birds which feed their young with "crop milk" include pigeons, doves and flamingos.