Animal genetic resources for food and agriculture crop and livestock species in the early neolithic time period changed our human evolution and lifestyles. This ability to control food production led to major demographic, technological, political and military changes. Consecutively, thousands of years of natural and human selection, genetic drift, inbreeding, and crossbreeding have contributed to the diversification of animal genetic resources and increased the variety of environments and production systems that livestock keeping takes place. Relatively few species have been domesticated; out of the world's 148 non-carnivorous species weighing more than 45 kg, only 15 have been successfully domesticated. The proportion of domesticated birds used for food
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