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Bird

12:09

Greater Sage Grouse: The Bird With The Voice Of A Champagne Bottle

3:07

5 Signs Your Bird Considers you it's Mother

15:22

4K HDR Video – Beautiful Lovebird | Budgies and Cockatiel Birds Playing and Feeding

20:16

Small BIRDS 8K ULTRA HD with Names and Sounds

Birds, also known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich. They rank as the world’s most numerically-successful class of tetrapods, with approximately ten thousand living species, more than half of these being passerines, sometimes known as perching birds. Birds have wings which are more or less developed depending on the species; the only known groups without wings are the extinct moa and elephant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in flightless birds, including ratites, penguins, and diverse endemic island species of birds. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming.
    • Evolution and classification 

    • Definition 

    • Dinosaurs and the origin of birds 

    • Early evolution 

    • Early diversity of bird ancestors 

    • Diversification of modern birds 

    • Classification of bird orders 

    • Genomics 

    • Distribution 

    • Anatomy and physiology 

    • Skeletal system 

    • Excretory system 

    • Reproductive system 

    • Respiratory and circulatory systems 

    • Heart type and features 

    • Organisation 

    • Nervous system 

    • Defence and intraspecific combat 

    • Feathers, plumage, and scales 

    • Flight 

    • Behaviour 

    • Diet and feeding 

    • Water and drinking 

    • Feather care 

    • Migration 

    • Communication 

    • Flocking and other associations 

    • Resting and roosting 

    • Social systems 

    • Territories, nesting and incubation 

    • Parental care and fledging 

    • Brood parasites 

    • Sexual selection 

    • Inbreeding depression 

    • Inbreeding avoidance 

    • Ecology 

    • Relationship with humans 

    • Economic importance 

    • In religion and mythology 

    • In culture and folklore 

    • In music 

    • Conservation