By Jillaine Burton, Open Door Bird Sanctuary

vulture2_kurt

Turkey vultures, like all birds, descend from dinosaurs. Photo by Kurt via Flickr Creative Commons

The next time you see a red-tailed hawk swoop in on its prey or a turkey vulture soaring in the sky, take time to appreciate the fact that you’re witnessing one of the last remnants of the dinosaurs. That’s right. Our feathered friends belong to the same family tree as the beasts that roamed the earth more than 100 million years ago. They are much more attractive than crocodiles and alligators (other dinosaur descendants with which birds have a lot in common). And it may well be that their size and ability to fly were the reason birds survived when Velociraptors did not.

Paleontologists first noticed the similarity between birds and reptiles in the 16th century. And in 1860, a quarry worker found the first fossil of an archaeopteryx, which was suspected to be the transitional form that linked traditional reptiles and birds. It was less than 50 years ago, however, that the connection between dinosaurs and birds was firmly established.

The dinosaur family is immense. Birds are most closely related to the two-legged theropods, a line of dinosaurs that includes Tyrannosaurus rex and Velociraptors. They share major skeletal characteristics, including large eye openings in the skull; hollow, thin-walled bones; a stiff tail and a foot with three functional toes. Due to recent discoveries of feathered dinosaurs in China, scientists believe that wings, feathers and other birdlike features slowly developed in theropods over tens of millions of years. Feathers appeared to come first, appearing on dinosaurs the size of cats and dogs. The development of wings and the ability to fly evolved as this line of dinosaurs shrunk in size.

velociraptor

Birds are most closely related to Velociraptors (above) and Tyrannosaurus rex. Photo by Alyse & Remi via Flilckr Creative Commons

Shrinking their way to survival?

This shrinking began about 200 million years ago and accelerated rapidly. One research team estimated that this dinosaur lineage was shrinking 160 times faster than other lineages were growing. The rapid miniaturization suggests that smaller birds must have had a strong advantage over larger ones. Their shrinking stature was also an important precursor to flight. While some larger animals can glide, flight powered by beating wings requires a certain ratio of wing size to weight. During this time, birds also developed the beak, a remarkable structure that has been described as a “pair of fingers” on the face. Beaks allowed birds to find food, clean themselves, make nests and care for their young.

dino

Part way through the evolutionary process, we can imagine dino-birds would look like this.

Fossil evidence suggests that once the fundamental body design for what we call birds was complete, there was a sudden evolutionary burst that produced thousands of different species. The cause is unknown, as are the reasons birds’ ancestors survived the Cretaceous crisis 65 million years ago while other dinosaurs did not. One theory is that birds’ small size and their ability to fly gave them more flexibility in adapting to rapidly changing environments. Whatever the reason, be glad that it happened and tip your cap to one of the oldest families on the earth.