No, chickens, or hens, cannot produce milk. However, some birds, like pigeons and flamingos, do produce a substance called crop milk, which is similar to mammalian milk. Crop milk is produced by both male and female pigeons, and by male penguins. It contains fat and protein, but no carbohydrates, and is a holocrine secretion, unlike the apocrine secretion of mammalian milk. Crop milk also contains antibodies from the parents, which activate genes in the immune system and contribute to the gut microbiome of the squabs that eat it. Squabs eat crop milk exclusively for the first three days after hatching, and continue to receive it until they are about 28 days old