How the Aftermath of an Owl Invasion Became a SNOWstorm
Since 2013, Project SNOWstorm has been using cutting-edge technology, like solar-powered GPS/GSM transmitters, to study the winter ecology of snowy owls like this one, called Amishtown, in Pennsylvania. Image thanks to ©Alan Richard
Scott Weidensaul, Naturalist, author, and one of Project SNOWstorm’s co-founders. Image: ©Beth Sanders
By Scott Weidensaul
It's hard to find anyone who is ambivalent about snowy owls. These huge, white Arctic raptors, with their riveting lemon-yellow eyes, have an unmistakable charisma.
Coming south in winter, they bring a slice of the Arctic with them, connecting temperate latitudes to the Far North in a way few other creatures can. You're not going to see a polar bear walking through your neighborhood, but if you live in southern Canada or the northern United States -- especially the Northeast, the Great Lakes, the northern Plains, or Pacific Northwest -- there's a decent chance that a snowy owl may be around this winter.
An Owl Invasion Starts a SNOWstorm
Every three to five years, thanks to a boom in lemming populations in the Arctic and a productive nesting season, large numbers of snowy owls "irrupt" south into southern Canada and the northern United States. Image thanks to ©Alan Richard
Yet until recently, we knew less about the winter ecology of these massive raptors, when they're sharing the southern landscape with us down here than we did about their breeding ecology in the distant Arctic. That began to change in a dramatic way during the winter of 2013-14 when, in the wake of a largest invasion of snowy owls into the East since at least the 1920s, a group of us founded Project SNOWstorm (www.projectsnowstorm.org).
✍︎Editor’s Note: This is one of the only avian websites that allows you to follow individual birds over the course of a season. It is fascinating.
It quickly grew into one of the largest snowy owl research projects in the world, with a team of roughly 40 biologists, researchers, banders, and wildlife veterinarians who largely volunteer their time and expertise. (The capital letters, by the way, refer to the four-letter bird-banding code for the species: SNowy OWl.)
Together We Fuel The World’s Largest Snowy Owl Dataset
Captured at a metropolitan airport where it was in serious danger, this freshly tagged male snowy owl is about to be released on the Maryland coast, part of a study on determining best practices for such relocations. Image thanks to ©Chris Hudson
Funded entirely by small, tax-deductible contributions from the public, and small grants from birding groups and other nonprofits, we've now tracked the movements of more than 90 snowy owls, [and] tagged them with cutting-edge transmitters in 16 states and provinces from Alaska to the Dakotas, the Great Lakes to Québec and Maine south to Maryland. In the process, we've documented many rarely observed or poorly understood behaviors in these majestic birds while creating -- by orders of magnitude -- the largest movement dataset in the world for this species.
How Snowy Owl Tracking Works
The tracking devices we use are known as GPS/GSM transmitters, which use two technologies most of us carry in our phones. Each unit communicates with the GPS satellite system overhead, continually logging incredibly accurate locations -- latitude, longitude, altitude, and flight speed, as frequently as every six seconds. Then, at regular intervals (usually every two days), it sends the data to us via the GSM cellular telephone network. When the owl migrates north in spring, beyond the cell network, the unit continues to store all its data, and when the owl migrates south again in early winter, we'll get tens of thousands of backlogged GPS points showing every detail of its summer breeding season.
Good fences make good neighbors; tracking data show that these two adult female snowy owls, Chippewa and Whitefish, in Michigan rarely trespassed on each other's territory. Thanks to ©Project SNOWstorm and Google Earth
The detail revealed by these transmitters of the daily lives of snowy owls has been breathtaking. And nightly lives; one of the facts about snowy owl ecology that [the transmitters] make clear is that these owls are not, as many birders and naturalists assume, primarily diurnal. In the summer Arctic, when the sun never sets, they have no choice, but in winter they are most active from dusk to dawn, and unless people or larger raptors harass them, [the owls] tend to roost all day quietly. (We've seen that tagged snowies in publicly accessible locations, like parks and beaches, tend to [be] bumped and pushed continually from point to point by people who get too close.)
Our tracking data have revealed aspects of snowy owl behavior that have never been recorded in such detail. Although snowies specialize [prey] primarily on small mammals like lemmings and voles during the breeding season [in the Arctic], their [more southern] winter diets are incredibly diverse. Many owls that winter along coastlines -- either the Great Lakes or marine environments -- specialize in hunting ducks, grebes, gulls, and other waterbirds, often quite some distance from shore.
Snowy Owls are not above scavenging; one owl on the Delmarva defended a bloated old dolphin carcass from turkey vultures, much as snowy owls in the Arctic have been seen to feed on bowhead whale carcasses. But each owl is an individual; some snowies, surrounded by immense numbers of waterfowl, hew entirely to land, hunting only for rabbits and other small mammals in tidal marshes and dunes.
Living on Ice, What Are the Snowy Owls Eating?
Norman Smith, a SNOWstorm co-founder, has been studying snowy owls in Massachusetts since 1981, and has removed thousands of snowy owls from Logan Airport in Boston. Here he is releasing “Duxbury.” Image thanks to ©Raymond MacDonald
Snowies, especially on the Great Lakes, but wherever else they have the opportunity, also show a great affinity for ice. Some of our tagged owls have spent up to six weeks at a time out in the middle of Lake Erie, which at the time they were there, was almost completely frozen. What on earth could they be eating, we wondered? Soon, the tracking data -- combined with daily satellite images of the lake -- revealed their secret.
The owls were haunting the edges of thin leads of open water, created by prevailing winds splitting and shifting the vast ice plates that covered the lake. These young owls seemed almost to be practicing for behavior [our] Canadian colleagues have documented in the Arctic. There, some adult snowies move north in winter, out onto the Arctic sea ice, to hunt ducks and auks in permanent openings in the ice pack known as polynyas.
Project SNOWstorm co-founder Steve Huy and his daughter Rowan take measurements on a snowy owl (Sinepuxent) that they trapped for tagging on the Maryland coast. Image thanks to ©Steve Huy
All of the tracking data for all of our owls is publicly accessible (though updates on actively tracked owls are delayed by 24 hours to give the birds some breathing space from curious humans). The SNOWstorm website, www.projectsnowstorm.org, has interactive maps that anyone can explore. We're also happy to share our raw data with students and teachers looking for real-life material for classroom projects.
Three years' worth of migration data show the nomadic summer movements of "Wells," a female originally banded in Maine. Thanks to ©Project SNOWstorm and Google Earth
One of the most important aspects of our work focuses on perhaps the most dangerous place a snowy owl can appear -- at an airport. Snowies are attracted to airports because the sites are wide open, flat, and treeless, much like the owls' Arctic home -- and to a snowy owl, a jet is no more frightening or alien than a tree or a building. Unfortunately, snowy owls can be as dangerous to a passenger jet as the plane is to the owl, and in the past airport, authorities have often killed snowy owls to remove the threat.
Because they are flat, open and treeless, airports are especially attractive -- and dangerous -- to snowy owls. Image thanks to ©Wayne Laubscher
One of SNOWstorm's founders, Norman Smith of Massachusetts Audubon, has been trapping and relocating snowy owls from Logan Airport in Boston since 1981. At Logan and a dozen other airports in the U.S. and Canada, we have tagged more than 40 such relocated owls in order to understand better how they behave following their relocation and to determine the best practices -- how far, how quickly, in which direction and into what habitats -- to move owls so they stay away from the airfield. SNOWstorm is supporting the work of Rebecca McCabe, an American Ph.D. student at McGill University in Montréal, who is heading up the relocation study as part of her dissertation.
Determining (Man-Made) Threats to Snowy Owls
"Dorval," an adult female snowy owl that had been previously relocated from the Montréal airport (hence the blue markings on her wings), flies off with a transmitter. She nested this past summer in northern Quebec, and returned south this winter to Ottawa. Image thanks to ©Guy Fitzgerald
Another critical aspect of Project SNOWstorm's mission is a better understanding of snowy owl health. We have a team of top wildlife veterinarians and pathologists, led by Dr. Cindy Driscoll of the Maryland Department of Natural Resources. This team works with state, provincial, and federal agencies to salvage snowy owls that have died from vehicle collisions, plane strikes, electrocution, rodent poisoning -- the gamut of human-related dangers they face. Cindy and her team have necropsied more than 260 snowy owls and conducted lab tests on blood and other samples taken from many more live birds captured for banding and tagging.
This life was not wasted. From left, Dr. Cindy Driscoll of Maryland Dept. of Natural Resources, Dr. Sherrill Davison and Dr. Erica Miller of University of Pennsylvania, handle necropsies and laboratory analysis of hundreds of salvaged snowy owls that were killed by vehicles, planes or other mishaps. Image thanks to ©University of Pennsylvania
These studies allow us to assess the health of the wider snowy owl population; those old myths about starving owls to the contrary, for example, most snowy owls that die from accidents are in good health and pleasingly plump. That said, we have found some disturbing evidence of widespread environmental toxins. Like many raptors, in general, these days, many snowy owls show some level of rodenticide poisoning in their tissues. Even at sublethal levels, these potent rat poisons can cause damage like uncontrolled hemorrhaging from wounds. We often find DDE, the breakdown product of the long-banned pesticide DDT, along with trace amounts of heavy metals and other contaminants.
Snowy Owls Carry Evidence of a Poisoned Environment
By necropsying hundreds of snowy owls found dead, Project SNOWstorm's veterinary team has dramatically increased our understanding of how environmental toxins and other dangers impact this species. Image thanks to the ©University of Pennsylvania
The biggest surprise, however, has been worrisome levels of methyl-mercury in the tissues of many owls. This air pollutant, generated primarily by coal-fired power plants and automobile exhaust, precipitates out of the air. Once in aquatic ecosystems, methyl-mercury begins to "bioaccumulate" -- increasing in concentration with every step up the food chain, until predators at the top, like snowy owls, may carry dangerously high levels, especially if they are feeding on waterbirds like ducks, grebes, and gulls. At high levels, mercury can cause a host of reproductive or behavioral problems. Because mercury accumulates more quickly in freshwater versus marine systems, we're hoping to use our tracking data to learn if snowy owls that hunt over, say, the Great Lakes are at greater risk than those feeding along ocean coasts or those hunting mammals at inland sites.
Together You and I Fuel Snowy Owl Research
The core team of Project SNOWstorm at a planning meeting (prior to COVID-19 and definitely not in the winter). Research in 2020 has been more difficult due to the pandemic, but carries on. Image thanks to ©Lauren Gilpatrick
✍︎Editor’s Note: Project SNOWstorm does this important work on a shockingly tiny budget Every donation counts. And don’t forget to sign up to follow your favorite snowy owls on their journey!
Back into the wild. What will this beautiful snowy owl teach us? Tom McDonald of Rochester, NY, in one of the most experienced snowy owl banders in the country, and a core member of the SNOWstorm team. Image: Thanks to ©Aaron Winters
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