[{"data":1,"prerenderedAt":148},["ShallowReactive",2],{"encyclopedia_en:\u002Fentsiklopediya\u002Fchto-takoe-ptitsy":3,"alt-locale:encyclopedia_en:\u002Fentsiklopediya\u002Fchto-takoe-ptitsy":109,"section-listing:disabled":110,"section-listing:encyclopedia_en:\u002Fentsiklopediya":111,"related-covers:en:\u002Fentsiklopediya\u002Fotryady-ptic|\u002Fslovar\u002Flinka-u-ptic|\u002Fslovar\u002Finkubaciya-yaic":142},{"id":4,"title":5,"body":6,"coverImage":72,"description":73,"extension":74,"faq":75,"imagePrompt":82,"meta":83,"navigation":84,"order":85,"pageType":86,"path":87,"publishedAt":88,"readingMinutes":89,"relatedLinks":90,"seo":103,"sitemap":106,"stem":107,"tags":85,"updatedAt":85,"__hash__":108},"encyclopedia_en\u002Fentsiklopediya\u002Fchto-takoe-ptitsy.md","What Is a Bird",{"type":7,"value":8,"toc":65},"minimark",[9,14,41,48,52,55,58,62],[10,11,13],"h2",{"id":12},"the-traits-that-define-a-bird","The traits that define a bird",[15,16,17,18,22,23,26,27,30,31,34,35,40],"p",{},"Birds form a distinct class of vertebrate animals, ",[19,20,21],"strong",{},"Aves",", set apart from all other animal groups by a specific combination of traits rather than any single one. ",[19,24,25],{},"Feathers"," are the clearest defining trait — no other living animal group has them, and every bird has them, even flightless species that use feathers purely for insulation and display rather than flight. Birds are also ",[19,28,29],{},"warm-blooded"," (endothermic), maintaining a constant, typically quite high body temperature regardless of the surrounding environment, and they ",[19,32,33],{},"lay hard-shelled eggs"," rather than giving birth to live young, with ",[36,37,39],"a",{"href":38},"\u002Fen\u002Fslovar\u002Finkubaciya-yaic","incubation"," keeping the developing embryo warm until it hatches.",[15,42,43,44,47],{},"Birds also share a ",[19,45,46],{},"toothless beak"," — no living bird has teeth, a trait lost over evolutionary time in favor of a lighter skull, though some extinct bird ancestors did have teeth. Their skeleton is built around flight even in species, like ostriches and penguins, that no longer fly: hollow, air-filled bones reduce weight, and a keeled breastbone (the sternum's prominent central ridge) anchors the powerful flight muscles used to beat the wings — or, in flightless species, muscles repurposed for other functions like swimming.",[10,49,51],{"id":50},"flight-is-common-but-not-universal","Flight is common but not universal",[15,53,54],{},"Flight is strongly associated with birds but is not, by itself, what defines the class — several bird lineages have lost the ability to fly entirely while retaining every other trait that makes them birds. Ostriches, emus, and cassowaries rely on powerful legs for running instead, while penguins use flipper-like wings for swimming rather than flying through air. Because these species still have feathers, a toothless beak, and the reproductive and skeletal features shared across all birds, they remain firmly classified as birds despite the loss of flight itself.",[15,56,57],{},"This same logic explains why bats are not birds despite also flying: flight evolved independently in bats (mammals, with fur, live birth, and milk-feeding of young), in birds, and in the long-extinct flying reptiles called pterosaurs — three unrelated lineages that each solved the challenge of powered flight in their own way, a pattern biologists call convergent evolution.",[10,59,61],{"id":60},"where-birds-fit-in-the-animal-world","Where birds fit in the animal world",[15,63,64],{},"Birds are most closely related, among living animals, to crocodilians — both groups descend from a shared reptilian ancestor, and birds are now understood by paleontologists to be the direct descendants of a specific lineage of theropod dinosaurs, making birds, in a very real evolutionary sense, dinosaurs that survived. This connection is visible in details like scaled legs (a trait shared with reptiles) alongside the feathers, keeled sternum, and other traits unique to the bird lineage that emerged from that dinosaur ancestry over tens of millions of years.",{"title":66,"searchDepth":67,"depth":67,"links":68},"",2,[69,70,71],{"id":12,"depth":67,"text":13},{"id":50,"depth":67,"text":51},{"id":60,"depth":67,"text":61},"\u002Fimages\u002Fentsiklopediya\u002Fchto-takoe-ptitsy.png","Birds are a class of warm-blooded, egg-laying vertebrates defined by feathers, a beak without teeth, and a skeleton adapted for flight — even in species that no longer fly.","md",[76,79],{"q":77,"a":78},"Are bats birds, since they also fly?","No. Bats are mammals — they have fur, give live birth, and nurse their young with milk, none of which are true of any bird. Flight evolved independently in birds, bats, and (long extinct) pterosaurs, a case of convergent evolution rather than shared ancestry, so flight alone doesn't define what a bird is.",{"q":80,"a":81},"Do all birds fly?","No. Ostriches, penguins, and several other lineages have lost the ability to fly entirely, yet they still qualify as birds because they retain every other defining trait — feathers, a toothless beak, and the distinctive skeletal and reproductive features shared across the whole class, even though the flight-specific adaptations of that skeleton are no longer used for their original purpose.","Photorealistic macro photo, an extreme close-up of a Falco tinnunculus common kestrel's folded wing showing the layered structure of flight feathers, individual barbs and the hollow central shaft visible in sharp detail, soft natural side light emphasizing texture and the feather's herringbone pattern, muted neutral background, shallow depth of field, 16:9",{},true,null,"encyclopedia","\u002Fentsiklopediya\u002Fchto-takoe-ptitsy","14.07.2026",1,[91,95,99],{"label":92,"path":93,"description":94},"Bird orders","\u002Fentsiklopediya\u002Fotryady-ptic","How the roughly 10,000+ bird species are grouped taxonomically",{"label":96,"path":97,"description":98},"Molt in birds","\u002Fslovar\u002Flinka-u-ptic","How feathers, a defining bird trait, are replaced",{"label":100,"path":101,"description":102},"Egg incubation","\u002Fslovar\u002Finkubaciya-yaic","How bird eggs are kept warm until hatching",{"title":104,"description":105},"What Is a Bird — the traits that define the class","What actually defines a bird biologically: feathers, a toothless beak, egg-laying, and a flight-adapted skeleton — even in species that don't fly.",{"loc":87},"entsiklopediya\u002Fchto-takoe-ptitsy","S7_GJ8SiAgr05ZsUkxTCHceo5JTW3sRfLX2Y7ghDnEs",{"ru":84,"es":84},[],[112,116,121,126,131,136,137],{"title":113,"description":114,"path":93,"coverImage":115,"publishedAt":88,"order":85},"Bird Orders","Bird orders are the major taxonomic groupings above family — Passeriformes (perching birds) alone contains over half of all known species, with the rest split across raptors, waterfowl, waders, and more.","\u002Fimages\u002Fentsiklopediya\u002Fotryady-ptic.png",{"title":117,"description":118,"path":119,"coverImage":120,"publishedAt":88,"order":85},"How Many Bird Species Exist","Around 10,000 to 11,000 bird species are currently recognized worldwide, with the exact count shifting as taxonomists revise species boundaries and new species are described.","\u002Fentsiklopediya\u002Fskolko-vidov-ptic-sushchestvuet","\u002Fimages\u002Fentsiklopediya\u002Fskolko-vidov-ptic-sushchestvuet.png",{"title":122,"description":123,"path":124,"coverImage":125,"publishedAt":88,"order":85},"How to Use This Atlas","A practical guide to Bird Atlas's five main sections — species catalogue, families, regional atlas, glossary, and identifier — and which one to start with depending on your question.","\u002Fentsiklopediya\u002Fkak-polzovatsya-atlasom","\u002Fimages\u002Fentsiklopediya\u002Fkak-polzovatsya-atlasom.png",{"title":127,"description":128,"path":129,"coverImage":130,"publishedAt":88,"order":85},"Life Cycle of Birds","A bird's life cycle runs from egg through hatching, growth to independence, sexual maturity and breeding, to death — with the pace of each stage varying enormously by species.","\u002Fentsiklopediya\u002Fzhiznennyj-tsikl","\u002Fimages\u002Fentsiklopediya\u002Fzhiznennyj-tsikl.png",{"title":132,"description":133,"path":134,"coverImage":135,"publishedAt":88,"order":85},"Popular Bird Species","Some species draw disproportionate public attention — through familiarity, striking appearance, cultural symbolism, or an unusual behavior — regardless of how common they actually are.","\u002Fentsiklopediya\u002Fpopulyarnye-vidy-ptic","\u002Fimages\u002Fentsiklopediya\u002Fpopulyarnye-vidy-ptic.png",{"title":5,"description":73,"path":87,"coverImage":72,"publishedAt":88,"order":85},{"title":138,"description":139,"path":140,"coverImage":141,"publishedAt":88,"order":85},"Where Do Birds Live","Birds occupy virtually every habitat on Earth, from tropical rainforest to open ocean to Antarctic ice — with distribution shaped far more by climate and food than by any single continent.","\u002Fentsiklopediya\u002Fgde-obitayut-ptitsy","\u002Fimages\u002Fentsiklopediya\u002Fgde-obitayut-ptitsy.png",[143,144,146],{"label":92,"path":93,"description":94,"coverImage":115},{"label":96,"path":97,"description":98,"coverImage":145},"\u002Fimages\u002Fslovar\u002Flinka-u-ptic.png",{"label":100,"path":101,"description":102,"coverImage":147},"\u002Fimages\u002Fslovar\u002Finkubaciya-yaic.png",1787114565389]