In today’s Academic Minute, Dr. Daniel Ksepka of North Carolina State University describes the common ancestor of today’s swifts and hummingbirds.
Daniel Ksepka is a research assistant professor in the Department of Marine, Earth, and Atmospheric Sciences at North Carolina State University and a research associate of the North Carolina State Museum of Natural Sciences. His research uses data from the fossil record and extant organisms to answer questions about major evolutionary events. He earned his Ph.D. at Columbia University.
Dr. Daniel Ksepka – Hummingbird Ancestor Discovered
A new fossil discovery from the Green River Formation of Wyoming is helping us understand the evolution of two fascinating groups of birds. Swifts and hummingbirds don't look very much alike, but they are each other's closest living relatives. Over 50 million years ago they shared a common ancestor. Eocypselus rowei is a newly named extinct species that foraged over the now vanished Fossil Lake. One of these tiny birds died and sunk to the bottom of this lake, where oxygen depleted waters kept it from decomposing until it was buried and fossilized, feathers and all.
Eocypselus gives us some clues as to what the common ancestor of hummingbirds and swifts was like. This species branched off the evolutionary tree of birds before the hummingbird and swift lineages split from one another.
The new fossil bird is very small. It could easily fit in the palm of your hand. Its beak is wide. Its wings are neither long nor short, and its legs still show adaptations for perching, suggesting it may have rested in trees while waiting for passing bugs. Since the time of Eocypselus, swifts have continued to improve their wings for energetically efficient flight, allowing modern species to stay aloft all day chasing down insects. Hummingbirds on the other hand, use their short, blade-like wings in a completely unique flight stroke that let's them hover in midair while sipping nectar from flowers.
The lack of wing specialization and the tiny size of Eocypselus support the idea that a decrease is size proceeded new flight styles in swifts and hummingbirds. It would be hard to develop endurance fast gliding flight or hovering at large sizes. So, shrinking opened a new door for this avian lineage, clearing the way for some of the most interesting birds alive today.