How do seabirds survive plunge diving into the sea at 70 miles per hour without breaking their necks? A new University of Washington (UW) study offers an answer. Published on October 12 in the journal Anatomical Record, it shows that gannets and boobies have reinforced neck vertebrae: an extra contact surface joins several of them, and the bones are stockier than in other birds.
A northern gannet hunts by scanning the sea from about 100 feet up. When it spots a school of fish, it pitches into a nosedive and hits the water at high speed.
Why plunge diving seabirds are an engineering puzzle
A dive like this puts immense compressive pressure on the head and neck. According to the UW team, engineers usually favour short, fat structures for anything built to handle compression. Gannets do the opposite. They have long, slender necks with 15 stacked vertebrae that bend slightly in an S-curve.
Earlier studies showed that the muscles around these vertebrae help lock them in place before impact. But, the researchers note, few studies had looked closely at the actual shape of diving birds’ neck bones.
How the researchers studied plunge diving necks
The team collected specimens of diving and non-diving birds from the Burke Museum. They ran CT scans to build detailed 3D models of the neck vertebrae, then analysed them with geometric morphometrics, a statistical method that compares biological shapes using fixed landmarks.
“Birds that rotate their heads side to side, or move them front to back, separate out from birds that use their heads in compression,” said lead author Megan Vanderberg, a UW biology graduate student at Friday Harbor Labs. “We see that the birds that plunge-dive have more robust vertebrae. They’re thicker, wider, and also shorter, shaped more like a square.”
The extra facet that protects plunge diving birds
Two features stood out. The first is the stocky, block-like shape of the vertebrae. The second is an additional contact surface, called an articular facet, on the second through sixth vertebrae. The researchers think this extra facet stops the neck from bending backward when the bird hits the water at an angle. Instead, the load is passed down the neck.
Kingfishers, which also dive, showed block-like vertebrae too, but not the extra facet. The study also found that kingfishers and the larger plunge divers experience the same force per neck area during a dive. In both groups, peak force arrived nearly five milliseconds after impact.
What this study does and doesn’t tell us
On the positive side, the work fills a gap in how we understand bird anatomy, and the team believes the link between structure and function could help palaeontologists identify plunge-diving birds from fossils. Senior author Bart Boom, a postdoctoral scholar at Friday Harbor Labs, said studying the birds’ biology helped explain how they survive these impacts.
There are limits, though. This is a shape-based study of museum specimens. The idea that the extra facet stops backward bending is what the researchers “think”, not something tested directly in live birds. The team says its next step is to study in more detail how force travels down the neck. Any engineering applications are, for now, a possibility rather than a result.
If you enjoy science that changes how we see familiar things, you may also like our explainer on the first working nuclear clock and our look at why slow research labs risk falling behind.
My view on plunge diving research
As a writer, I feel this is the kind of story that reminds us nature has already solved problems engineers are still working on. A long, thin neck shouldn’t survive a 70 mph impact with water, yet it does, thanks to a small extra contact surface and squarer bones. I like that the team is careful about what it has shown and what it still needs to test.
FAQ: plunge diving seabirds
How fast do gannets hit the water when plunge diving?
According to the University of Washington, a northern gannet can break the water’s surface at about 70 miles per hour after diving from around 100 feet.
Why don’t plunge diving birds break their necks?
The study found stockier vertebrae and an extra contact surface, called an articular facet, on the second to sixth neck vertebrae of gannets and boobies. Researchers think this helps pass the load down the neck instead of letting it bend backward.
Do kingfishers have the same neck adaptation?
Partly. Kingfishers also have block-like vertebrae, but the researchers did not find the extra facet in them.