Crop milk bears little resemblance to mammalian milk, being a semi-solid substance somewhat like pale yellow cottage cheese. It is extremely high in protein and fat and contains more of it than cow or human milk . Both male and female adult birds produce crop milk and share in the feeding and care of the young.
Pigeon's milk begins to be produced a couple of days before the eggs are due to hatch. The parents may cease to eat at this point in order to be able to provide the chicks with milk uncontaminated by seeds, which the very young chicks would be unable to digest. The chicks are fed on pure crop milk for the first week or so of life. After this the parents begin to introduce a proportion of adult food, softened by spending time in the moist conditions of the adult crop, into the mix fed to the chicks, until by the end of the second week they are being fed entirely on softened adult food.
Pigeons normally lay two eggs. If one egg fails to hatch, the surviving chick gets the advantage of a supply of crop milk sufficient for two chicks, and by the end of the first week it is almost as big as two "normal" chicks would be.
The very high nutrient concentration of pigeon's milk makes it difficult to devise an artificial substitute for hand-rearing chicks. Various proprietary mixes are available. A good home-made mix can be made from equal quantities of dehydrated dried pure soya protein (with no added salt, flavourings, preservatives etc.) and Soya-based dairy-free butter-substitute (ordinary dairy butter is not suitable, as young pigeons' digestive systems cannot cope with dairy products). This is made into a runny paste with a little water, a tiny crumb of a multivitamin tablet and a tiny pinch of chalk (which is necessary for bone development to avoid splay-leg). The crop should be allowed to empty completely between feedings. With care and gentleness, it is possible to raise a pigeon on this mix from the moment of hatching.