Crop milk

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Crop milk is a secretion from the lining of the crop of parent birds that is regurgitated to young birds. It is found among all pigeons and doves where it is referred to as pigeon milk. An analog to crop milk is also secreted from the esophagus of flamingos and some penguins.

Video Crop milk

Comparison to mammalian milk

Crop milk bears little physical resemblance to mammalian milk, the former being a semi-solid substance somewhat like pale yellow cottage cheese. It is extremely high in protein and fat, containing higher levels than cow or human milk. It has also been shown to contain anti-oxidants and immune-enhancing factors. Like mammalian milk, crop milk contains IgA antibodies. It also contains some bacteria. Unlike mammalian milk, which is an emulsion, pigeon crop milk consists of a suspension of protein-rich and fat-rich cells that proliferate and detach from the lining of the crop. Lactation in birds is also controlled by prolactin, which is the same hormone that causes lactation in mammals.

Maps Crop milk

Feeding nestlings

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 squabs (baby pigeons and doves) with milk uncontaminated by seeds, which the very young squabs would be unable to digest. The baby squabs 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 squabs, 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 squab gets the advantage of a supply of crop milk sufficient for two squabs and grows at a significantly faster rate. Research suggests that a pair of breeding pigeons cannot produce enough crop milk to adequately feed three squabs, which explains why clutches are limited to two.

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Cultural references

• In Animal Crossing: Wild World for the Nintendo DS and Animal Crossing: City Folk for the Wii, a character named Brewster uses it as an ingredient when serving coffee to long-time customers.
• In the reality TV series Flavor of Love during Season 2, the father of Deelishis requests a carton of pigeon milk at dinner.
• Ptasie mleczko (Polish: bird milk) is the name of Polish candy, which variations are also popular in Eastern Europe countries as Ptichye Moloko (Russian: ?????? ??????), ptashyne moloko (Ukrainian: ??a???? ??????).

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References

src: www.wildthingssanctuary.org

External links

• Article on Bird Milk from stanford.edu
• Article on the relationship between crop milk and clutch size in Mourning Doves (.pdf)
• Smithsonian National Zoo article on Common Crowned Pigeon, includes paragraph on crop milk

Source of the article : Wikipedia