Crop milk is described as

• A. It is regurgitated by parents for the first few days
• B. It is produced by the crop of mammals
• C. It is identical to mammalian milk
• D. It is not nutritious

Answer: (A)

Crop milk is a milk-like, nutritious secretion produced in the crop of certain birds (not mammals) that is regurgitated by the parents to feed the chicks during the first days after hatching. It is formed by the lining cells of the crop and secretions that create a protein- and fat-rich substance, which the parents feed to the young by regurgitation. This is why the correct description emphasizes that it is regurgitated by the parents for the initial days of the chick’s life. The other statements don’t fit: it isn’t produced by mammalian mammary glands, it isn’t exactly mammalian milk, and it is indeed nutritious for the newborns.