(noun) A semi-solid, crumbly excretion high in fat and protein that some birds feed to hatchlings. Unlike mammalian milk, crop milk or bird milk does not have any calcium or carbohydrates. It is only fed to young birds for a few days until they are able to digest other foods, and parent birds may gradually mix adult food in with the young birds' diet to wean them off crop milk. To feed on crop milk, young birds will stick their bills into their parents' mouths to stimulate the production and release of the milk. Both male and female birds can and do produce crop milk to care for their young.
All pigeons and doves feed their young crop milk. For these species, the milk contains sloughed off cells from the inside of the parents' crop. Flamingos produce bird milk through glands along the digestive tract, and young flamingos eat this milk until they have developed the mature filter feeding apparatus in their bills to allow them to feed on mature food. Penguins will also generate a milk-like substance from the esophagus to feed young chicks if other food sources are scarce.
Photo – Greater Flamingo Feeding Chick © jim gifford
Pigeon's Milk, Pigeon Milk, Bird Milk