Birds are dinosaurs

Birds sit inside Dinosauria. They are the living continuation of theropod dinosaurs, not a neighbouring class that merely resembles them.

Cladistics does not grade animals by vibe. It follows shared ancestry. Theropods — the line of Tyrannosaurus and Velociraptor — include Archaeopteryx and, inside them, modern birds. Wishbones, hollow bones, brooding postures, feathers on non-flying theropods: the nest is one nest.

‘Non-avian dinosaurs’ is the careful phrase for what died at the end of the Cretaceous. Avian dinosaurs did not. A chicken is not a cousin of dinosaurs. It is one, in the only sense taxonomy still uses.