In the silt-red soil of China’s Gansu Province, a little owl has lain for about 6 million years, since an epoch known as the Late Miocene. The fossilized bird’s claws are outstretched, one of its wings is spread wide, and its sharp bill is turned back over its shoulder.
You could imagine this little hunter crashing into an unsuspecting mammal one chilly night long ago. But an analysis of the fossil published Monday in the Proceedings of the National Academy of Science suggests the scene probably needs to be played in daylight: Judging by the size and shape of its eye sockets, the owl hunted under the sun, in instead of the moon. The fossil could provide clues as to the evolutionary forces that transformed this bird and some other species into the owl equivalent of a morning person.
The fossil owl, an extinct species the researchers have named Miosurnia during the day, has been beautifully preserved, said Li Zhiheng, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences and an author of the new paper. This allowed the team to take accurate measurements of its bones, something not possible with most other fossil owls. They then fed the bird’s dimensions into a computer program that made predictions about an organism’s lifestyle, comparing the data to the anatomy of a variety of reptile and bird species.
Owls are best known for their nocturnal hunting and hooting, and indeed many modern owls are nocturnal. They mainly prey on creatures that are also awake at night. The eyes of night owls have many more rod cells than cone cells, allowing them to see better in low light.
But some birds are crepuscular, meaning they emerge at dawn and dusk, and still others, a small handful of burrowing owls, are diurnal, meaning they are active during the day. Scientists suspect that these daywalkers evolved from nocturnal ancestors, meaning they shifted their period of activity sometime in the past. But there are no clear answers to explain how a limited range of owls could thrive during the day.
The fossil in the new study has elongated eye sockets and rings of bone around the eyes. These shapes resemble those of modern day owls. The researchers found that with eyes this size and shape, the owl is more likely to see in daylight. Of course, said Dr. Li, with no one around to observe the owl in action, researchers have to make educated guesses — no one knows for sure what this owl’s behavior was.
But if some owls were transitioning to daily lifestyles as early as six million years ago, it may be possible to find clues as to what prompted them to make this change in what we know about their environments. The part of Gansu Province where the fossil was found is near the Tibetan Plateau, and it was likely a cold, harsh place to live, said Dr. Li. Perhaps the small mammals owls hunted evolved away from nocturnal activity to take advantage of warmer daytime temperatures. They might have drawn their predators, over the eons, to the light themselves.
For now, the group is looking forward to analyzing another already unearthed, well-preserved owl of a different species, one they suspect was also diurnal and could provide additional clues as to why some owls made this jump.
“There are more stories to tell about the eye,” said Dr. Li.