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Doug Leier: GPS study helps shed light on waterfowl migration patterns

Advances in technology are generating more confident results in the movements of waterfowl no matter the time of year.

Advances in technology are providing biologist more accurate information on waterfowl. Photo courtesy North Dakota Game and Fish Department

The lack of winter snowpack created a bit of mystery as to when the spring snow goose migration would begin, which route the birds would take and if the lack of snow would slide the geese through without delay.

Coming up with the answer was a combination of biology, gut feeling and observation.

Luckily for waterfowl biologists, advances in technology are generating more confident results in the movements of waterfowl no matter the time of year.

“From a waterfowl ecology perspective, it’s difficult to study ducks in late summer because birds are moving and shuffling around a lot,” said Mike Szymanski, North Dakota Game and Fish Department migratory game bird management supervisor.

With previous technology, Szymanski said biologists would have been driving around in vehicles or flying in airplanes with VHF transmitter receivers trying to find marked birds that could have moved hundreds of miles.


“With the advancements in technology, specifically batteries getting smaller, we had the ability to pursue a GPS transmitter study to look at some of the aspects of post-breeding mallards after they start to fledge or attain flight in late summer,” Szymanski said. “The study design also lends itself to many other uses. With the data, we’ll be able to work the project from many angles and figure out a lot of movement and migration dynamics of mallards in fall.”

Cynthia Anchor, a South Dakota State University master’s student who spent considerable time in the field capturing ducks, is responsible for managing the GPS data and eventually analyzing and writing up the results of the two-year study in North Dakota and South Dakota. While there is a ton of data to further analyze, Anchor said she was surprised by some of the movements the marked mallards had made.

“We had one bird, for example, that was marked south of Bismarck that moved up to Canada and spent most of the pre-migration period in Canada,” she said. “We had another bird that left North Dakota, went to Arkansas and then moved to eastern Ohio. So, we’re seeing some movements that are going to be really tricky to explain.

“We have seen birds that were marked from all over, kind of converge into the same general areas, especially in northeastern South Dakota,” Anchor added. “I think the first year, we had two or three birds from North Dakota and two birds from South Dakota all using the same random wetland in South Dakota at the same time. And none of those birds were related, none were marked together. They just happened to end up in the same place.”

While it’s easy to understand ducks pointing their bills south and migrating to warmer climates during the leaner months, Szymanski said people don’t immediately think birds move north, east or west before their actual migration.

“Having the ability to collect data in between harvest and marking is very beneficial to painting the picture of their movements,” Szymanski said. “We’re still looking at the movements, trying to figure out if there is a connection to the directions that they go, the distances they go, and how it possibly relates to habitat, weather and other factors.

“I’m a waterfowl hunter and I knew coming in this was going to be part of the project, and it’s been kind of interesting to hear some of the stories from hunters,” Anchor said. “In North Dakota, our very first bird was harvested by a 10-year-old, a new hunter who had never shot a mallard before.”

Leier is an outreach biologist for the North Dakota Game and Fish Department. Reach him at dleier@nd.gov.

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