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 only other species, but also cameras, a car alarm and a chain saw. Broadcast 2 December 1998, this programme discusses mating rituals. If a male bird is on the lookout for a partner and has a suitable nest, it must advertise the fact, either by its call, a visual display or both. The frigatebird provides an example of the latter, with its inflated throat pouch. The hornbill's courtship, among that of many others, also runs to the offer of a gift. For some species, dancing can also be an important component, and grebes are shown performing a "pas de deux".