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
The Life of Birds kind of dance to flush out the aquatic inhabitants. Skimmers have different-sized mandibles, the lower one being used to skim the water's surface for small fish. Ducks have developed an assortment of angling skills. Some dabble, like the mallard, while others are of a more streamlined design and are at home underwater, such as the merganser. Waders, which specialise in feeding on mud flats at low tide, include avocets, godwits, dowitchers and sanderlings. The pelican feeds in groups, their pouch-like bills being more successful when used collectively. Boobies fish in the open ocean and are shown dive-bombing shoals "en masse".