Bird anatomy Birds have a four-chambered heart, in common with mammals, and some reptiles (mainly the crocodilia). This adaptation allows for an efficient nutrient and oxygen transport throughout the body, providing birds with energy to fly and maintain high levels of activity. A ruby-throated hummingbird's heart beats up to 1200 times per minute (about 20 beats per second). Many birds possess a muscular pouch along the esophagus called a crop. The crop functions to both soften food and regulate its flow through the system by storing it temporarily. The size and shape of the crop is quite variable among the birds. Members
Food and drink prohibitions fairly recent addition to cultural food prohibitions is the meat and eggs of endangered species or animals that are otherwise protected by law or international treaty. Examples of such protected species include some species of whales, sea turtles, and migratory birds. Similarly, sustainable seafood advisory lists and certification discourage the consumption of certain seafoods due to unsustainable fishing. Organic certification prohibits certain synthetic chemical inputs during food production, or genetically modified organisms, irradiation, and the use of sewage sludge. The Fair Trade movement and certification discourage the consumption of food and other goods produced in exploitative working conditions. Other social