What is the dinosaur that is a bird?

Dinosaurs evolved into birds. First by growing feathers (probably for mating displays, then flight)

Answer:Birds do have many features in common with theropods (bipedal carnivorous dinosaurs) which suggests that they had a common ancestor. We dont know that this common ancestor was a dinosaur though. It may well have been a bird (see related links).

Looking back in time through the theropod fossil record, these dinosaurs appear to be more bird-like the further back in time you look. Raptors are known to have had feathers and were fairly bird-like, but Archaeopteryx was much more bird-like and lived much earlier and may have been an ancestor of the raptors. There is also a controversial fossil called Protoavis that was dated even earlier and was more bird-like still, with hollow bones like modern birds.

So birds may have been around throughout the mesozoic era and even pre-date the dinosaurs. We have little record of them though because their hollow bones decompose very easily so are less likely to leave fossils. We do have some very ancient bird footprints though (see link).

It may be more accurate to call the theropods Flightless Birds, rather than calling birds dinosaurs.