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
Handbook of the Birds of the World a non-profit endeavour fuelled by material from more than one hundred contributors from around the world. In early 2013, Lynx Edicions launched the online database HBW Alive, which includes the volume and family introductions and updated species accounts from all 17 published HBW volumes. Since its launch, the taxonomy has been thoroughly revised and updated twice (once for non-passerines and once for passerines), following the publication of the two volumes of the "HBW and BirdLife International Illustrated Checklist of the Birds of the World". The Handbook of the Birds of the World Alive site also provides a free access 'Key