Summary
Feathered, warm-blooded vertebrates with wings and lightweight bones, most of which fly.
In depth
Feathers, beaks without teeth, hollow bones, high metabolic rate, four-chambered heart and efficient one-way airflow through lungs and air sacs. Birds are living dinosaurs (theropods).
Birds have a high metabolic rate and lay hard-shelled eggs. Courtship songs and displays are well developed. Beak shapes reflect diet.
Remember: birds are a surviving dinosaur lineage.
Birds descended from theropod dinosaurs, with fossils such as Archaeopteryx and feathered Chinese dinosaurs showing the transition. Adaptations for flight include a lightweight skeleton, fused bones, a keeled sternum, efficient lungs and a high metabolic rate with endothermy. They lay hard-shelled eggs and often show extensive parental care and elaborate courtship. Birds have excellent vision (including UV in many), and some navigate using magnetic fields.
There are about 11,000 species. Beak shape reflects diet. Song is learned in songbirds, parrots and hummingbirds through brain circuits similar to speech learning, and involves a critical period. Birds are important seed dispersers, pollinators and pest controllers. About 1 in 8 species are threatened, and the passenger pigeon and dodo are extinct.
Key idea: a bird's one-way airflow through air sacs gives continuous oxygen uptake, allowing flight at altitude.
Frequently asked questions
What is Birds?
Feathered, warm-blooded vertebrates with wings and lightweight bones, most of which fly.
Which area of biology covers Birds, and how advanced is it?
Birds is one of the 53 topics in Zoology & Animal Diversity. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Bird Flight Adaptations, Mammals, Reptiles.
Can you give an example of Birds?
Hummingbirds hover with figure-eight wing motion.
What should I learn before Birds?
Birds is a Beginner topic, so no earlier topic is required. Other Beginner topics in Zoology & Animal Diversity that pair well with it include Animal Kingdom, Vertebrates and Invertebrates, Sponges.
What topics are related to Birds?
The closest topics to Birds are Bird Flight Adaptations, Mammals, Reptiles, Amphibians. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Birds?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Birds. To practise the whole of Zoology & Animal Diversity, use the Zoology & Animal Diversity quiz.
How is Birds different from Bird Flight Adaptations?
Birds: Feathered, warm-blooded vertebrates with wings and lightweight bones, most of which fly. Bird Flight Adaptations: Hollow bones, keel, air sacs and feathers combine to deliver lift and efficient respiration. Read both side by side and note what each one explains.
How should I study Birds step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Bird Flight Adaptations and explain the difference aloud. Finally, take the Zoology & Animal Diversity quiz and come back to this page for any question you miss.