Birds

Living dinosaurs with feathers, wings, and a talent for ignoring your car, and the world has more than 11,000 species of them.

By Greg Goodwin · Published November 4, 2026

Cheat Sheet

Species count: 11,167 in the eBird/Clements Checklist v2025 and 11,131 in AviList v2025; totals vary by checklist.
Families: 251 extant families in the 2025 eBird/Clements Checklist (AviList v2025 lists 252).
Oldest fossil bird: Archaeopteryx, about 150 million years old, with feathers and wings but also toothed jaws and a long bony tail.
Distance record: a juvenile bar-tailed godwit flew more than 8,435 miles nonstop in 11 days from Alaska to Tasmania in October 2022.
Arctic tern: roughly 44,000 miles of migration per year is a commonly cited estimate; figures vary by source and by bird.
Decline: North America had about 2.9 billion fewer breeding birds in 2019 than in 1970, a 29% drop across 529 species.

The 60-Second Version

Birds are warm-blooded, feathered animals that lay hard-shelled eggs, and they are the living branch of the dinosaur family tree. Most can fly, though ostriches and penguins are famous for not bothering. They live on every continent and in nearly every habitat, from rainforest canopies to open ocean, and they fill jobs that range from pollinating flowers to cleaning up carcasses to spreading seeds. They also sing, build, migrate, and mimic, which is why people have watched them for centuries. How many species exist depends on which authority's checklist you consult, since scientists still argue over where one species ends and the next begins. The count currently sits a little above eleven thousand. Anyone can take part in the counting, because millions of birdwatchers submit sightings that scientists use to track which species are thriving and which are slipping.

The Long Version

Dinosaurs With Better Publicity

The scientific consensus is that birds descend from the dinosaur lineage, specifically from small feathered theropods, in the Jurassic period, more than 150 million years ago. The first known fossil bird, Archaeopteryx, is dated to about 150 million years ago. It had feathers and wings but also toothed jaws and a long bony tail, a blend that made it a landmark for the dinosaur connection. Huxley proposed the link in the nineteenth century, and later discoveries, including Deinonychus and feathered fossils from China, strengthened it. Research on feathered theropods suggests feathers first served for insulation or display, with flight coming later.

How Many Kinds of Birds? Depends Who Is Counting

There is no single official number. The eBird/Clements Checklist v2025, released by the Cornell Lab of Ornithology on October 31, 2025, counts 11,167 species, 20,261 subspecies, and 251 families, a net gain of 22 species over the previous year after 40 gained through splits and 18 lost through lumps. A unified list called AviList, released in June 2025 by a working group including BirdLife International and the Cornell Lab, counts 11,131 species. Earlier lists ranged from 11,017 to 11,524. The IOC World Bird List, which updates twice a year, is another major authority. Differences come from taxonomy, the judgment calls about what counts as a distinct species.

Built to Fly, Except When Not

Flight shaped bird bodies, but it did not define every bird. Feathers insulate, signal, and camouflage as well as lift, and the research on feathered dinosaurs suggests they were in use long before anything took off. Beaks come in shapes suited to nectar, seeds, fish, and carrion. Passerines, the perching birds that include most songbirds, supply many of the everyday visitors to backyard feeders. Hummingbirds, raptors, owls, parrots, pigeons, woodpeckers, and ducks are each their own distinct branches of the family. A species-level view therefore matters: any statement about how birds live applies to some groups and fails for others.

Marathon Migrations

Migration is where birds show off. Estimates for the Arctic tern vary, but commonly cited figures run to roughly 44,000 miles a year, and Audubon reports some tracked individuals logging more than 50,000 miles in a single year. In October 2022, a juvenile bar-tailed godwit nicknamed B6 flew more than 8,435 miles nonstop in 11 days from Alaska, where it was born, to Tasmania, Australia. An earlier satellite-tracked godwit flew about 7,145 miles from Alaska to New Zealand in nine days without stopping to eat, drink, or rest. These flights depend on stopover habitats and weather, so the routes are only as safe as the places along them.

Counting, Decline, and Citizen Science

A 2019 study in the journal Science, led by Cornell Lab of Ornithology scientist Rosenberg, estimated that the United States and Canada had about 2.9 billion fewer breeding birds than in 1970, a 29% decline. It analyzed 529 species using volunteer survey data and a network of 143 weather radars. Grassland birds fell by 53%, about 720 million birds, and more than 90% of the loss came from just a dozen bird families. Waterfowl and raptors increased, which researchers linked to conservation efforts. The study did not isolate a single cause, but pointed to habitat loss, urbanization, and pesticides as likely contributors.

Why People Care

Birds are one of the easiest wild animals to notice, so they act as a daily gauge of environmental health. Learning a few basics turns a walk or a window view into a game, and sightings you log can feed real science.

Glossary

Theropod: A group of mostly meat-eating, two-legged dinosaurs, including the lineage that gave rise to birds.
Taxonomy: The science of naming and classifying living things, which decides how many species a checklist counts.
Passerine: A perching bird, the group that includes most songbirds such as sparrows, warblers, and finches.
Subspecies: A geographically distinct population within a species that is recognized as a named variant.
Flyway: A broad route that migrating birds follow between breeding and wintering areas.

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