The Secret Life of Ducks
After dark on Feb. 9, 2021, Doug Osborne and his student-biologist crew from the University of Arkansas at Monticello drove to a series of wire duck traps set up in a bottomland hardwood forest (BLH) greentree reservoir (GTR) site south of Altheimer.
In the three days these traps had caught more than 1,000 mallards on which Osborne and crew had attached aluminum U.S. Fish and Wildlife Service leg bands. The bands were part of a study that, since 2015, has banded more than 21,000 mallards to track the distribution, movements and survival of those that spend at least part of the winter in Arkansas.
Osborne would also attach 20-gram satellite-transmitters to five mallards — three males and two females. The transmitters were an extension of the banding study and their signals would be picked up by satellites to hourly record the mallards’ precise locations.
This data would help biologists learn when and where mallards would migrate to breeding areas in the spring and return in the fall. It would show specific migration routes and stopover times, correlation of movements with climate events and landscape, habitats used, how birds respond to hunting pressure and other biological phenomena.
A friend who sponsored Osborne’s transmitters named the birds “Heitmeyer 1-5” in recognition of the nearly 20 years I have helped the family restore and manage their lands for waterfowl. In an epic journey across North America, Heitmeyer 1, was still alive and spent the past winter practically in my southeast Missouri backyard.
While one year of movements by a few birds does not establish definitive trends for the millions of mallards that migrate through North America each year, the journey of these birds sheds light on aspects of duck biology hunters can only dream about.
The Journey Begins
Within a few days of the transmitters being attached, an Arctic blast brought record cold, with ice sheets and heavy snow, to the state. Four of the birds stayed close in Arkansas while a fifth, a female, was found dead near Humphrey after the February storm.
Female mallards are more sensitive to cold weather events than males, in part because of their smaller body mass, and mallards remaining far north during winter are mainly male, suggesting body mass and fat reserves are critical to withstand prolonged periods of cold, snow and absence of food.
Heitmeyer 1 stayed at local, ice-free areas on Hallowell Reservoir at the Bayou Meto WMA and the Stickpond reservoir at Cornerstone — which were sanctuary areas during hunting season.
In the first week of March, the mallards all took different routes north and, by early May, all had settled to breed in or near the Prairie-Parkland Pothole Region (PPR) of the Dakotas and southern Canada. Band recovery data from Arkansas have shown a preponderance of breeding derivation from that area.
Biologists have generally believed mallards travel along major river corridors as primary “duck interstates” during fall and spring migration south of the PPR, and that they stop at interstate “gas stations” — quality wetland habitats — where they refuel, rest and prepare for the next leg of the journey. Heitmeyer 1 generally followed this pattern from central Arkansas to southeast Missouri, where it paralleled the Mississippi River to its first “gas station” in the Fox and Des Moines River valleys of northeast Missouri and southeast Iowa.
Each of the first flights covered at least 500 nonstop air miles, with three birds flying directly over the inhospitable Ozark Mountains — indicating that the fat reserve “gas tanks” of the birds had been filled with quality foods obtained in Arkansas habitats. Each movement also coincided with warm southerly flow winds aloft — the true “tailwinds” of the waterfowl world.
Heitmeyer 1 settled to breed in one of the few wetter PPR areas — a complex of wetland basins west of Brookings, South Dakota. After about a month the bird moved west to the Watertown, South Dakota, area, where it spent the balance of the summer, apparently molting and staging for fall migration.
Being a duck is not easy, and it is sometimes hard to understand how we still have so many. Heitmeyer 1-5 epitomized the struggle for survival.
By November, 2021, two of the four mallards no longer transmitted location signals (the transmitters have a temperature mode that quits sending when the bird does not move for a period of time) and likely were dead.
Heitmeyer 1 and 2 made relatively fast, direct, movements from breeding/staging areas to winter destinations, stopping only in larger river floodplain areas where refuges and more permanent water were present.
Both birds arrived and stayed at locations in Iowa and Missouri for the balance of fall and winter — far north of the central Arkansas sites they used the previous winter.
Both did not leave until relatively late in fall when northern areas experienced strong cold fronts, ice cover on shallow wetlands and some snow cover, and both flew along previously used “safe” routes to stopover sites and to final wintering areas.
In early November, Heitmeyer 1 flew from the Goose Lake Wildlife Area near Grover, South Dakota, to wetlands south of Des Moines in a path essentially identical to that used in April 2021. This movement coincided with the first strong cold front of the fall in the north.
The general movement pathway from Des Moines through northeast Missouri, south to St. Charles, and then to southeast Missouri was also similar to that used in spring 2021.
Heitmeyer 1 and 2 rode out storms and winter weather to stay in southeast Missouri and central Iowa, respectively, until they began their northward migrations in March.
Some of the ducks used ponds, rivers and wetlands in urban locations during their travels. Just like Canada geese that reside in, or commonly use, urban areas, this may be simply a survival adaptation to escape increasing hunting pressure and exposure to harvest mortality in traditional rural migration and winter locations.
It also begs the question of whether the gene pool of wild mallards is being diluted with domestic stock genetics. A recent study found that more than 30% of mallards sampled in the Mississippi Flyway carried domestic mallard DNA, and this trend may be increasing.
Heitmeyer 1 spent three months in my “backyard,” on and near the Mingo NWR and the Duck Creek Conservation Area (CA) in southeast Missouri. What were the chances a mallard fitted with a transmitter at Cornerstone, where I had worked for nearly 20 years, would come see me in Missouri?
Thanks to protection and management, the Mingo-Duck Creek area is one of the largest contiguous tracts of BLH remaining in the Mississippi Alluvial Valley north of central Arkansas. It also is the first sizable block of BLH that mallards encounter during fall migration and has been a destination for millennia.
Heitmeyer 1 only left Mingo and Duck Creek four times. The first was after heavy rains and regional flooding in late December. It came to one of my personal WRP properties, in the Dark Cypress bottoms where I have restored BLH and managed moist-soil habitats over the past decade. In early March Heitmeyer 1 again returned to the Dark Cypress bottom for four days during a flood along the Castor River.
The bird moved off Mingo twice after the close of hunting season in mid-January, when it visited private duck club wetlands containing remnant natural slough, Cypress brake, and floodplain swale habitats.
What Was Learned
Heitmeyer 1 appears to be a true timber mallard. Its selection of BLH in the Bayou Meto Basin in winter 2021, use of floodplain forests and wetlands along larger rivers during fall and spring migration across the U.S., and wintering at Mingo during 2021-2022, reflect evolutionary forces that have shaped mallard adaptations to, and reliance on, BLH, even in today’s drastically modified landscapes.
Heitmeyer 1 very rarely visited agricultural fields. So, its prolonged stay in southeast Missouri and failure to migrate further south, even during cold and ice periods, had nothing to do with the flooded crop fields — a contradiction of certain theories about the cause of increased northern wintering of mallards in the Mississippi Flyway.
Instead, Heitmeyer 1 stayed north in the Mingo Basin because of mild winter weather, abundant, high-quality BLH food and cover, freedom from hunting disturbance and traditions likely imprinted by preceding generations.
The travels of Heitmeyer 1 and the other transmitter mallards demonstrate the importance of protecting and carefully managing wetlands in natural ways and places, especially BLH, throughout North America.
Conservation of waterfowl in North America is a continental enterprise. No doubt, the success in sustaining waterfowl populations in North America has been because of protection and careful management of NWRs, state and provincial wetland areas, WPAs, privately-owned WRP and duck club lands and other habitats along traditional riverine and prairie/parkland regions.
A vigilant commitment to continued support of wetland conservation across North America is critical.