Reader Dominic has called my attention to two new reports from the BBC about the gyrfalcon (Falco rusticolis), pronounced “JER-falcon.”
First, a bit about the bird. It’s the world’s largest falcon, with some specimens reaching three pounds with a four-foot wingspan. They’re magnificent birds:
Photo by Doug Backlund; go to his page for many more great photos of the bird
Here’s the range map from Cornell’s All About Birds; they breed on the North American tundra but range widely south. A map of its worldwide distribution, including Greenland, northern Europe and Asia can be found here.
They’re bird eaters; the Cornell site reports that they “eat mostly ptarmigan, but many other prey species have been recorded, including fulmars, gulls, jaegers, ducks, geese, Rough-legged Hawk, Short-eared Owl, sparrows, buntings, and redpolls.” Here’s an amazing video of one taking a ptarmigan on the wing: the strike occurs at about 2:15 (I find the music annoying; you might want to turn it off).
So what’s new about the bird? Two discoveries, both made by a team headed by Kurt Burnham, a Ph.D. student at Oxford’s Edward Grey Institute of Field Ornithology.
1. The gyrfalcon is basically a seabird. As the BBC reports, up to now its hunting habits during the nonbreeding season—the winter—were largely unknown. But tracking the birds with radiocollars shows gyrfalcons to be “secret seabirds”:
Gyrfalcons living in the high Arctic overwinter out at sea, spending long periods living and hunting on pack ice.
It is the first time any falcon species has been found regularly living at sea.
The birds likely rest on the ice and hunt other seabirds such as gulls and guillemots, over what appears to be one of the largest winter ranges yet documented for any raptor.
“I was very surprised by this finding,” said ornithologist Kurt Burnham who made the discovery. “These birds are not moving between land masses, but actually using the ice floes or pack ice as winter habitat for extended periods of time.”
“Previously, all species of falcon were considered to be land-based birds.”
. . . Those on the east coast ranged far more widely, covering between 27,000-64,000 square kilometres. Some of these had no obvious winter home ranges and travelled continuously during the non-breeding period, spending up to 40 consecutive days at sea.
During the winter one juvenile female travelled more than 4,500km over 200 days, spending over half that time over the ocean between Greenland and Iceland.
2. Some gyrfalcon nest sites are ancient. Another report, from BBC EarthNews, shows that the nesting areas used by these birds can be several thousand years old. Like other falcons, gyrfalcons don’t build nests, but simply scrape out an area on a rock ledge. New research shows this:
Carbon dating revealed that one nest in Kangerlussuaq in central-west Greenland is between 2,360 and 2,740 years old, the researchers report in Ibis.
Three other nests in the area are older than 1,000 years, with the youngest nest site first being occupied 520 to 650 years ago.
These ancient nests are still being regularly used by gyrfalcons.
“While I know many falcon species re-use nest sites year after year, I never imagined we would be talking about nests that have been used on and off for over 2,000 years,” says Burnham.
They also carbon-dated some gyrfalcon feathers to over 600 years old. But these aren’t the oldest continuously used nesting sites by birds, not by far:
By carbon dating solidified stomach contents, peat moss deposits and bone and feather samples from various moulting sites, researchers have in the past shown that colonies of snow petrel have returned to the same sites for 34,000 years and adelie penguins for 44,000 years.