By Luke Naylor and Andrew Raedeke, Ph.D.
Where are the ducks? Sometimes we can find the answer simply by checking out another part of a marsh or expanding our scouting area. Other times, however, these searches are in vain, which might lead us to conclude that ducks are absent from our part of the world. Are they north? Are they south? Are they all on a sanctuary? Likewise, waterfowl managers wonder where to restore and manage waterfowl habitat, how much is needed, and what proportion of this habitat should be set aside as sanctuary. Answers to these questions, along with those of hunters, require a thorough understanding of duck movements and habitat use during the nonbreeding season.
Biologists know that dabbling ducks seek out resources in various habitats during fall and winter to complete a series of life-cycle events, such as the molt, pair bonding, and fat and protein accumulation. Decades of banding research helped define the routes that waterfowl follow during migration and can identify major stopover and wintering locations, but migration and habitat use by individual birds is less understood. Fortunately, technology and public interest recently intersected, creating an opportunity to broaden our understanding of mallard migration and habitat use during the nonbreeding period.
During the early 2000s, a combination of declining duck populations and mild winters had hunters and biologists wondering if migration patterns were changing. In 2004, the Arkansas Game and Fish Commission (AGFC) embarked on a project capitalizing on new technology to track the movements of individual mallards throughout their annual cycle. Unlike more traditional radio telemetry methods, new satellite transmitters provided researchers with the ability to follow individual mallards thousands of miles from their wintering grounds to their breeding grounds. During 2004−2007, AGFC biologists marked nearly 200 mallards with satellite transmitters, mostly prior to spring migration. Other partners soon joined this effort, including the Mississippi Department of Wildlife, Fisheries, and Parks; Ducks Unlimited; the Mississippi Flyway Council; the Central Flyway Council; the USDA Natural Resources Conservation Service (NRCS); and the Livingston Ripley Waterfowl Conservancy. In total, partners in this study marked nearly 300 mallards in Arkansas, Mississippi, and Saskatchewan.
Dr. Susan Sheaffer of the Livingston Ripley Waterfowl Conservancy and Dr. Richard Malecki, a professor emeritus at the Cornell Lab of Ornithology, provided expertise on marking birds and evaluating the performance of transmitters. Dr. David Krementz, of the Arkansas Cooperative Fish and Wildlife Research Unit at the University of Arkansas, and his students analyzed thousands of readings obtained from the nearly 200 mallards marked in Arkansas. More recently, Dr. Bill Beatty and Dr. Dylan Kesler of the University of Missouri teamed with Dr. Lisa Webb of the Missouri Cooperative Fish and Wildlife Research Unit to use GPS satellite telemetry data to determine which habitats mallards frequented during migration and winter.
But back to our original question, "Where are the ducks?" Fall migration often is perceived by hunters to be a drawn out affair, with ducks trickling down the flyways from north to south in response to weather events and habitat conditions. It's easy to imagine a scenario in which the migration might last a few months, beginning in mid-October and ending in mid-January. Instead, satellite-marked mallards completed fall migration in less than a month on average, with the majority of the birds starting their southward journey almost a month before freeze-up. In fact, 20 percent of the ducks marked in Arkansas during the winters of 2004−2007 returned south the next fall in one nonstop flight.
By plotting the locations of satellite-marked birds throughout the year, researchers gained a better understanding of the movements and habitat preferences of mallards at both continental and regional levels. PHOTO: Gang Wang, DU
While fall migration is of greatest interest to hunters, waterfowl habitat conditions during spring migration may be more important to duck populations. The observation of satellite-marked birds during our study revealed that mallard migration strategies are more flexible in spring than in fall. The average length of spring migration varied by year, ranging from 18 days to 48 days, with an average stopover time of about 12 days while en route. More than 75 percent of satellite-marked mallards from Arkansas either nested in the Prairie Pothole Region or migrated through the region en route to their eventual nesting destination.
This research has helped to fill in missing pieces of the puzzle of mallard movements and how the birds use habitat, including newly restored habitats. Since 1990, the NRCS has worked with over 11,000 private landowners to protect more than 2.6 million acres of wildlife habitat through the Wetlands Reserve Program (WRP). The precision of GPS satellite telemetry units has enabled University of Missouri researchers to confirm that mallards use WRP wetlands frequently during migration and winter. Researchers have also documented that areas with large wetland complexes—especially those along the Mississippi and Missouri river corridors—are used more frequently than are more isolated wetlands. On a daily basis, local movements of satellite-marked mallards averaged only about two miles, and most were less than eight miles. For hunters, this would suggest that complexes of quality habitat will offer better hunting than fragmented habitat. For waterfowl managers, it suggests that restoring wetlands in close proximity to one another will likely be of greater benefit to waterfowl than spreading out wetlands across the landscape.
An unexpected benefit of this partnership was that it enabled waterfowl hunters to access the same information available to waterfowl biologists. The AGFC partnered with the Center for Advanced Spatial Technologies at the University of Arkansas to develop a website displaying locations of marked birds. While no longer online, this website provided a unique opportunity for the public to track the mallard migration as it unfolded across this continent. Tracking individual birds offers a fascinating look at the variation in duck behavior and the birds' habitat preferences. As hunters and scientists watched the movements of mallards across the landscape in nearly real time, together they could begin answering questions about duck movements and habitat selection that could improve hunting prospects and bolster future conservation efforts.
Luke Naylor is waterfowl program coordinator for the Arkansas Game and Fish Commission. Dr. Andrew Raedeke is a resource scientist with the Missouri Department of Conservation.
Mallard Tracking Facts
- The average distance traveled by satellite-marked mallards during spring migration was more than 730 miles. The average distance traveled by individual birds during fall migration was almost 875 miles.
- One of the first mallards (a drake) ever marked with a GPS satellite transmitter in Arkansas flew more than 500 miles during spring migration, from Minnesota to Saskatchewan, in only four days.
- This same bird made a remarkable one-day flight in early fall from Saskatchewan to south-central Iowa—a distance of more than 900 miles!
- Although fall migration commonly is thought of as a one-way trip, several mallards in the tracking study made south-to-north movements during fall and winter.