Crop milk

Common card · No. 206104

Crop milk is a secretion from the lining of the crop of parent birds in some species that is regurgitated to young birds. It is found among all pigeons and doves, where it is also referred to as pigeon milk. Crop milk is also secreted from the crop of flamingos and male emperor penguins, suggesting independent evolution of this trait. Unlike in mammals where typically only females produce milk, crop milk is produced by both males and females in pigeons and flamingos, and in penguins, only by the male. Lactation in birds is controlled by prolactin, which is the same hormone that causes lactation in mammals. Crop milk is a holocrine secretion non-sex specific in response to brooding unlike in mammals where milk is an apocrine secretion. Crop milk contains both fat and protein, as with mammalian milk, but unlike mammalian milk, it contains no carbohydrates.

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