For #EvolutionEvents Episode 6, we turn to birds and dinosaurs! Birds, seabirds and otherwise, are critical to healthy ecosystems in the Salish Sea. A famous species in the Salish Sea is pictured here (right image), the bald eagle (Haliaeetus leucocephalus).
Many of you may already know that today’s birds are “modern dinosaurs”, sharing high relation to some of the most awe-inspiring and frightening dinosaurs we know from history.
How did this happen?
Well, over many millions of years and processes of evolution. A critical piece of evidence to us today was discovered in 1861, a fossil representing a creature called Archaeopteryx (a dinosaur-bird “hybrid” from the late-Jurassic, left image). The idea that dinosaurs had led to birds, hatched and took off in the 1960’s, with the discovery of a fascinating predatory, small and feathered dinosaur fossil; a creature called Deinonychus that could answer a lot of “dinosaur to bird” questions, as if a missing puzzle piece. This creature was believed to give rise to modern birds today.
The mechanisms into how small, modern-looking birds evolved from massive dinosaur giants required a fair amount of time…the changes necessary to “be a bird” started to occur about 200-160 million years ago; this does not mean that birds existed at this point in time. Experts believe that feathers and smaller body sizes, important qualities of modern birds, evolved with certain theropods prior to birds emerging. Later, wings and flight, among other changes, would lead to the beginning of birds. The entire process from dinosaur to bird, though variably discussed, is stated to be fairly step-wise and logical. Today, not all birds utilize flight; but the ancestors of today’s birds utilized flight to set them apart from their dinosaur relatives. The ability to fly was lost with some bird groups in more recent history.
So then, what type of dinosaurs are modern birds related to- the mighty T.Rex or a four-legged creature like the Stegosaurus? Birds evolved from some of our most popularized dinosaurs, theropods, which were two-legged, meat-eating dinosaurs. And yes, the T. Rex was a theropod!
Why did birds emerge?
Scientists suggest that some smaller theropods began to move into trees seeking food, safety and living space, evidently opening up vast new niches in the process. Over time, it is suggested that natural selection favoured smaller birds who would be better suited for tree-living and eventually flying. To quicken the pace of being small, it is suspected that there may have even been embryonic events that, in short, make scientists relate adult birds to baby dinosaurs. These events also helped to change skull shape and give new opportunities for the beak to appear.
Many bird groups were also lost from the Cretaceous extinction (K-T) that was known for the extinction of non-avian dinosaurs. Some bird groups, of course, did survive and persist to be today’s wonderfully diverse songbirds, seabirds and more.
Sources: National History Museum, Scientific American, Bird Life International, Britannica, Science News for Students.
Written by: Alexa D., B.Sc. Marine Naturalist with Five Star Whale Watching.