Birds are dinosaurs. They descended from a group of dinosaurs called theropods and, because they are dinosaurs, birds are also reptiles. Wondering if this is scientifically
controversial? It isn’t.
Early on when the dinosaur-bird link was being discovered, circa 1860, scientists differed in their opinion as to whether or not the link existed. This was largely because the connection between birds and dinosaurs was centered around the famous fossil Archaeopteryx, which had, like birds, fused clavicles—a wishbone. (Just like the wishbone in your Thanksgiving turkey.) The problem surrounding the wishbone discovered in Archaeopteryx was that, according to the information at the time, other dinosaur specimens did not have wishbones. So, the thinking went, even though birds might be related to Archaeopteryx, this didn’t mean that birds were related to dinosaurs. This is the juncture in which the idea that Archaeopteryx was an evolution of dinosaurs, and birds were related to them, became controversial.
The argument against the connection was, if birds are related to dinosaurs, why would they evolve to include a wishbone that their ancestors evolved without? It didn’t make sense from an evolutionary perspective. According to this argument, birds must not be related to dinosaurs, even though their ancestors may have coexisted.
The problem with this line of thinking for scientists was that wishbones didn’t fossilize very well and were prone to misidentification. Over the years, science improved and—as it turns out—dinosaurs do have wishbones, which means that Archaeopteryx was an evolution of dinosaurs and birds are related
Today, the evidence that supports the link between birds and dinosaurs is overwhelming. Along with the presence of a wishbone are feathers. Feathers are what make birds distinctly unique among other animals on Earth and recent fossils of theropod dinosaurs show that they too had feathers. In addition, modern-day birds have complex breathing structures (i.e., hollow bones connected to their respiratory system), and some theropods share this trait.
These days, it is generally agreed upon within the scientific community that birds are modern-day dinosaurs belonging to the theropod group. The most famous theropod is without a doubt Tyrannosaurus rex!
So, when you see a bird in the field or at your feeder, you’re looking at a modern-day dinosaur.