It’s not just mammals that “got milk.” Though we typically think of milk as the lactose-containing liquid that comes from mammary glands, scientists are discovering more species that give their babies a boost by making special substances for them. And these sort-of milks aren’t just nutrient rich, some contain stuff that help babies fight infection or establish a gut microbiome, just like mammalian milk. It’s proof that the animal world still has surprises left to discover.
Pigeons
Both female and male pigeons produce a nutritious white liquid from a food storage pouch in their throat, called a crop. Their squabs eat nothing but this “crop milk” for the first three days after hatching, then the adults start introducing them to pigeon food, though they continue to get crop milk until they’re about 28 days old. Like mammalian milk, scientists have found that crop milk contains antibodies from the parents, activates genes involved in the immune system, and contributes to the gut microbiome. Also, the hormone that stimulates milk production in female mammals, called prolactin, is also what promotes milk production in both male and female pigeons.
