Both male and female pigeons secrete milk through:

Explanation

Pigeons are noted for their unique ability to produce "pigeon's milk", a soft, cheesy and nourishing secretion, especially during the breeding season. It is formed by the degeneration of the epithelial cells lining the crop. It is regurgitated into the mouth of the young birds until they are old enough to manage a graindiet like their parents. The pigeon's milk includes water, fat, protein (casein) and lactose. The milk is produced by both sexes and contains 35 percent of fat.