So dinosaurs are not completely extinct?
Exactly.
The asteroid impact and other environmental changes at the end of the Cretaceous wiped out the non-avian dinosaurs about 66 million years ago. One dinosaur branch survived: birds.
That means the sparrow at your feeder belongs to a lineage that was already part of the dinosaur story long before humans existed.
It is one of my favourite bird facts because it changes how an ordinary backyard bird looks once you know it.
What kind of dinosaurs did birds come from?
Birds evolved within the theropods, a large dinosaur group that mostly walked on two legs.
Tyrannosaurus, Velociraptor, Deinonychus, and many smaller feathered dinosaurs also belonged to the theropod side of the family tree.
That does not mean a robin descended directly from a T. rex or that a Velociraptor simply turned into a bird. Think of them as relatives on branching lines. Birds came from smaller theropod ancestors within that much larger group.
What evidence connects birds and dinosaurs?
There is a lot more than feathers.
Birds and theropod dinosaurs share many skeletal features, including a wishbone or furcula, hollow or air-filled bones in parts of the skeleton, three-toed limbs, flexible wrists, and an S-shaped neck.
Fossils also show feathered non-avian dinosaurs, nests, eggs, brooding behaviour, and body plans that bridge what people once imagined as a sharp divide between "dinosaurs" and "birds."
The boundary turned out to be much fuzzier.
Did dinosaurs really have feathers?
Many did.
Fossil discoveries have revealed everything from simple filament-like coverings to complex feathers. Some feathered dinosaurs could not fly, which tells us feathers did not begin only as flight equipment.
Insulation, display, camouflage, and later aerodynamic uses all belong in the story.
Our page on why birds have feathers looks at what feathers do in living birds today.
What about Archaeopteryx?
Archaeopteryx is famous because it combines bird-like and dinosaur-like traits.
It lived roughly 150 million years ago and had feathered wings and a wishbone, but also teeth, clawed fingers, and a long bony tail.
It is an important early bird relative and a beautiful example of evolutionary transition. Scientists do not need it to be the single direct ancestor of every modern bird for it to matter.
Are chickens related to T. rex?
Yes, in the same broad sense that all birds are.
T. rex and modern birds are both theropod dinosaurs, but they sit on different branches of that family tree. A chicken is not a miniature T. rex descendant.
Still, look at a chicken's feet, posture, feathers, rapid head movements, and the way it runs. The dinosaur connection becomes easier to picture.
Are crows dinosaurs too?
Yes. So are ravens, robins, hummingbirds, eagles, pigeons, penguins, and every other living bird.
There are more than 10,000 living bird species worldwide, which means dinosaurs are still remarkably diverse.
Our Common Birds guides are, technically, a collection of living dinosaur profiles.
Why did birds survive when other dinosaurs did not?
Scientists are still studying the details, but survival probably involved a mix of small body size, diet, reproduction, and the ability of some early birds to live in environments that remained workable after the mass extinction.
Not every ancient bird survived. Many bird lineages disappeared too.
The modern groups came from the survivors that made it through a very difficult bottleneck.
Frequently asked questions
Are birds technically reptiles?
In evolutionary classification, birds belong within the larger reptile family tree as well as within Dinosauria. Everyday language usually keeps birds and reptiles separate because they look and live so differently.
Is a chicken a dinosaur?
Yes. Chickens are birds, and birds are avian dinosaurs.
Are crocodiles dinosaurs?
No. Crocodilians are close living relatives within the broader archosaur family, but they are not dinosaurs.
Did birds exist at the same time as dinosaurs?
Yes. Early birds lived alongside many non-avian dinosaurs long before the mass extinction 66 million years ago.
Keep following the bird body
Continue with why do birds have feathers?, do birds have hollow bones?, why do birds have different beaks?, or return to the Bird Facts hub.