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
Handbook of the Birds of the World Handbook of the Birds of the World The Handbook of the Birds of the World (HBW) is a multi-volume series produced by the Spanish publishing house Lynx Edicions in partnership with BirdLife International. It is the first handbook to cover every known living species of bird. The series is edited by Josep del Hoyo, Andrew Elliott, Jordi Sargatal and David A. Christie. All 16 volumes have been published. For the first time an animal class will have all the species illustrated and treated in detail in a single work. This has not been done before for any other group in