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
Birds of the Danube Delta final production represented by birds, the classification of these latter in categories with aquatic, mixed and respectively terrestrial nutritive regimes. In this respect, the delta birds appear as having a trophic regime of predominantly aquatic origin owing to the huge quantity the nutritive biomass of this milieu is produced in the Danube Delta in the warm season of the year. While the sedentary species generally close their trophic chains at the delta's level, the migratory, the passage, and the wintertime species annually carry away from the Danube Delta a great part of the nutritive biomass accumulated while resting in this