Local gyrfalcon Tinsel steals the show at bird lecture
Did you know that gyrfalcons, avian predators and the world’s largest falcons, keep the same mate year after year, but sometimes borrow other birds’ nests?
Michael Henderson and Devin Johnson shared these facts and other information from a longstanding study of gyrfalcons on the Seward Peninsula at their presentation at a Strait Science session May 13 at UAF Northwest Campus.
One such bird has resided in the Nome area with John, Marguerite and Ava Earthman for about 20 years. John Earthman, a falconer who assists biologists on various projects, brought Tinsel, his gyrfalcon, for show and tell at the lecture. Tinsel stood on her perch during the presentation, quiet, in gray and white feathered slendor on light-colored feet with black shiny talons.
At the end of the presentation, members of the audience gathered around Tinsel who perched on Earthman’s arm, ready for her close-up.
Henderson and Johnson on the other hand, observe gyrfalcons in the wild. Henderson is project manager for The Peregrin Fund, which funds the nonprofit’s Gyrfalcon and Tundra Conservation Program along with Boise State University and other partners, like Alaska Department of Fish and Game.
The two men have been working the Seward Peninsula this spring and summer, dangling from ropes, rappelling up cliffs and using ladders if necessary, to boost themselves up or let themselves down to peer into nests at gyrfalcon hatchlings and prey remnants.
Henderson and Johnson, with assistance of volunteers, attach leg bands and maybe replace batteries in cameras that monitor nesting activity, either motion activated or capturing slices of gyrfalcon family life every 30 minutes or so in a variety of nesting locations—stick nests in trees or sheltered by cliff overhangs or on ledges, maybe on dredges or other remnants of tundra activity.
The project monitors food sources throughout the reproductive pageantry from, say, mid-May to the end of July.
Gyrfalcons, formal scientific name, Falco rusticolus, live across the circumpolar Arctic—Iceland, Greenland, Russia, Europe and North America — where climate warming is opening up the Arctic two to four times faster than other parts of the globe.
Gyrfalcons, the largest of falcons, are not likely to live where there are no ptarmigan. Alaska’s state birds are pretty much the gyrfalcons’ No. 1 prey in early days of the reproductive season, balanced with almost as much ground squirrels, maybe close to 40 percent of each, with diets rounded out by about 15 percent shorebirds and a few percent songbirds, according to Johnson, a doctoral student at UAF Wildlife Conservation program.
Scientists have found diet trends suggesting that while the gyrfalcons are rearing their broods, the importance of ptarmigan and shorebirds decreases while dependence on ground squirrels and passerines—small perching birds —increases. As summer progresses, the nesting diet varies from fewer ptarmigan to more ground squirrels.
The scientists are researching how the nesting couples depend on certain prey during the reproductive season, and whether the changing climate has altered the availability of traditional prey and habitat when the gyrfalcons need it.
Another way to say that is “phenology mismatch,” when interacting species, say gyrfalcons and their prey, change the timing of regularly repeated phases in their life cycles at different rates.
Warming climate has already changed the habitat to present challenges from “shrubification,” increased growth of shrubs on the tundra that conceal lemmings, voles, hares, rabbits, marmots and other small ground prey to hide from gyrfalcon “fly overs.”
Henderson and Johnson are looking at primary food sources and the habitat required to sustain gyrfalcons. They are monitoring the changes to that habitat brought by climate warming, so that they can plan to mitigate current and predicted changes in the gyrfalcon’s world.
The pair of scientists credited study and assistance from many others in the study of gyrfalcons—Peter Bente, formerly of Nome, Travis Booms, David L. Anderson, John Earthman and his daughter Ava Earthman, who is working as a volunteer in the gyrfalcon program this summer.