Pigeons are known all-too-well by city-dwellers the world over. But what you might not know is that these birds produce a substance similar to milk for nourishing their young, and researchers have begun to understand how the critters do it. The pigeon version of “milk” is produced in fluid-filled cells within their crop, a specialized part of the esophagus typically used for storing food prior to digestion. Both male and female pigeons begin producing it about two days before their eggs hatch, and dutifully regurgitate the cottage cheese-like substance into their baby’s mouths for several weeks, after which they gradually introduce softened food to ready their young squabs for the real world.
A study published today in the journal BMC Genomics looks more closely at how pigeon milk is actually made. The researchers compared levels of gene expression between “lactating” and non-milk-producing cells, finding a high level of activation in genes involved with antioxidant synthesis and cell growth. This helps explain why their “milk” has high levels of antioxidants like carotenoids and is rich in fat, containing three times as much as cow’s milk. Wild-raised pigeon squabs die without it, and one study found that chickens raised on it grew 38 percent faster than chicks on a typical diet.
Pigeons aren’t the only birds that can perform this mammal-like feat: flamingos and male emperor penguins also produce a milk-like substance to feed their young. These adaptations appear to have evolved independently from one another, offering researchers enticing clues about the composition of various animal’s milk and the function of lactation, which is all-important for mammals.
Let’s just hope no enterprising beauty-product company latches onto this news and turns pigeon milk into the next hot skin treatment.