Digestion a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion. In some birds it is an expanded, muscular pouch near the gullet or throat. In adult doves and pigeons, the crop can produce crop milk to feed newly hatched birds. Certain insects may have a crop or enlarged esophagus. Herbivores have evolved cecums (or an abomasum in the case of ruminants). Ruminants have a fore-stomach with four chambers. These are the rumen, reticulum, omasum, and abomasum. In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and
Human uses of birds down are used for bedding, insulation, and other purposes. Birds were among the wild animals hunted for food before the Neolithic revolution and the development of agriculture. For example, in the Epipaleolithic of the Levant, between c. 14,500 and 11,500 BP, both waterfowl and migratory birds were eaten. Archaeologists have studied the return in terms of energy from captured food compared to the energy expended to capture it; birds provide a smaller return than larger game such as deer, but better than many plant materials. For example, waterfowl captured in a drive can yield a return of around 2,000 kcal/hour,