Tracking Snowy Owls

With cutting-edge tracking technology, we can follow the movements of snowy owls in astounding detail, and potentially for years at a time. This research has been made possible by the generous contributions of the general public and a variety of ornithological and birding organizations.

Collaborating scientists in Project SNOWstorm are tagging snowy owls with next-generation GPS-GSM transmitters made by Cellular Tracking Technologies of Rio Grande, NJ.

How they work

Baltimore basks in some mild spring sunshine on Long Beach Island, which was a hotspot in New Jersey for snowy owls this winter. (©Jim Verhagen)

Its black solar panel gathering sunshine, the small transmitter sits in the middle of a snowy owl’s back (©Northside Jim)

These solar-powered transmitters record locations in three dimensions (latitude, longitude and altitude) at programmable intervals as short as every 30 seconds, providing unmatched detail on the movements of these birds, 24 hours a day.

Unlike conventional transmitters, which report their data via Argos satellites in orbit, GSM transmitters use the cellular phone network. When the bird is out of range of a cell tower, the transmitters can store up to 100,000 locations, then transmit that information — even years later — when the bird flies within cell coverage.

The transmitters weigh about 40 grams — about as much as seven U.S. quarters, and only 1.5-3 percent of the bird’s weight. They are attached with a backpack harness made of low-friction Teflon ribbon that goes over the bird’s wings. Studies of snowy owls wearing conventional satellite transmitters in this fashion have found no evidence that they increase mortality or decrease breeding success (Therrien et al. 2012).

Still, we’re careful only to tag snowy owls that are in robust health. As experienced researchers, we assess every owl we catch to make sure it is in good shape, with normal weight and healthy fat stores. Any owl that seems questionable will not be tagged.


What have we learned?

A lot, much of it unexpected. Going into this study, little was known about the local and landscape-level movements of snowy owls on the wintering grounds, nor about their nocturnal hunting activity and range size — certainly not at the extraordinary level of detail these transmitters provide.

A closer look at Whitefish Point's and Chippewa's winter ranges -- with only a few points of overlap. (Project SNOWstorm and Google Earth)

Two adult female snowies, tagged in Michigan’s Upper Peninsula, barely moved a quarter-mile from their adjacent territories. (Project SNOWstorm and Google Earth)

We’ve found that some owls are home-bodies, and rarely move a quarter-mile from where they were banded. Others roam across hundreds of miles in a few weeks, moving from Atlantic barrier islands to Amish farm country and back to the coast.

We’ve shown how some snowy owls move out onto the frozen surface of the Great Lakes for weeks or months at a time, apparently hunting for waterfowl using the cracks that open and close endlessly between immense, wind-driven sheets of ice. (In this, they may be practicing a lifestyle some adult snowy owls follow in the Arctic, wintering on polynyas — areas of open water in the pack ice — where they hunt sea ducks.)

Millcreek's on-ice movements this winter. (©Project SNOWstorm and Google Earth; MODIS ice imagery by NOAA CoastWatch )

Some snowy owls spend weeks or months on the frozen Great Lakes. (©Project SNOWstorm and Google Earth; MODIS ice imagery by NOAA CoastWatch )

We confirmed a long-held suspicion that snowy owls feed heavily on birds in the winter, especially ducks, geese, grebes and gulls — and for the first time have documented in detail their hunting behavior at night over the open ocean, often using channel markers and buoys as hunting perches.

By necropsying snowy owls that are found dead from accidents, disease and other causes, and analyzing tissue samples, we have learned that these great hunters are exposed to a wide range of environmental contaminants, from rodent poisons to mercury to pesticide breakdown products like DDE, which may affect their behavior and reproduction.


Doodle-like tracks on Hudson Bay show where a snowy owl was riding an iceberg, pushed in great loops by wind and tide. (Project SNOWstorm and Google Earth)

Doodle-like tracks on Hudson Bay show where a snowy owl was riding an iceberg, pushed in great loops by wind and tide. (Project SNOWstorm and Google Earth)

To the north and back

Once the owls migrate north beyond the limit of the Canadian cell phone system, we lose direct contact with them — but their transmitters continue to log precise GPS locations, storing them up until the unit is back in cell range. When the owls migrate south the next winter (or the next, or the one after that) the units transmit their stored information, which represents the most detailed, granular record of the movement of owls in the Arctic and subarctic ever made.

Our tagged owls from 2013-14 and 2014-15 have summered in primarily in northern Nunavut and the Ungava Peninsula — sometimes drifting for days on icebergs in James and Hudson bays.

Surprises from the start

The very first owl we tagged provided some big surprises. Caught on Assateague Island in Maryland on Dec. 17, “Assateague” left two days later and flew north, loafing for a day on Cape Henlopen, Delaware, then crossing 38 miles of open water to reach the north shore of Delaware Bay. Then he moved down the New Jersey coast to the village of Reed’s Beach, where he spent a week. See Figure 1.

Leaving Reed’s Beach, he flew across southern New Jersey in the middle of the night, following the Tuckahoe River to the coast, then flying up the tightly-packed coastal towns to Atlantic City. Stopping briefly on the famous Steel Pier, he continued up the coast to the town of Brigantine, almost 100 straight-line miles (and more than 150 flying miles) from where he’d started just 11 days earlier. See Figure 2.

By contrast, a snowy owl tagged Dec. 23 in central Wisconsin has rarely roamed more than a mile from where it was caught, in the Buena Vista grasslands of Portage County. Project SNOWstorm is showing how different owls respond to different conditions. See Figure 3.

Our Goal

Thanks to the public’s generosity, in 2013-14 we were able to tag 22 snowy owls from Minnesota to Massachusetts with GPS/GSM transmitters, as well as conduct a range of DNA, chemical isotope, and toxicology studies. In 2014-15, we tagged an additional 12 owls, and watched as five of the first year-class came back south.

With your help, we are continuing our work this winter, in the field and the lab — tagging additional snowy owls, while continuing to monitor those we tagged previously. The transmitters cost roughly $3,000 each, and the generosity of private donors and bird conservation groups has made this work possible.

Any amount will help, and contributions are tax-deductible through the Ned Smith Center for Nature and Art, a 501(c)3 nonprofit.


Therrien, J-F., G. Gauthier and J. Bêty. 2012. Survival and reproduction of adult snowy owls tracked by satellite. Journal of Wildlife Management 76(8):1562-1567.