Scientists have discovered “super mom” Wood Ducks and how hunters in a few southern states are selectively killing them before they leave nesting areas.
By Rex Graham
In a paper published May 25, 2016, in The Auk, researchers from the University of Georgia and Auburn University reported that some Wood Duck females successfully hatched their young year after year while other seemingly robust females repeatedly failed. The results gathered over 11 years “were the opposite of our predictions,” the scientists reported.
Wood Duck ‘super mom’ traits
The features that make female Wood Ducks super moms are counter-intuitive:
- The most successful Wood Duck hens were not necessarily the largest or in prime condition.
- The wear and tear of raising ducklings didn’t reduce a super mom’s survival rate or success in her next breeding season.
- The age of individual super moms did not seem to influence her breeding success.
- The varying quality of wetland habitat in any given year didn’t matter: Wood Duck super moms tended to be successful mothers and survivors, regardless of habitat quality.
“The most important finding of this study is that there are significant differences in the parenting quality of individual female Wood Ducks,” said Gary Hepp a co-author of the study and Emeritus Professor of wildlife science at Auburn. “This has rarely been reported in ducks and never for Wood Ducks.”
Hepp and his colleagues found the super moms at the U.S. Department of Energy’s Savannah River Site in South Carolina. Hunting is prohibited on the 310-square-mile (800 sq km) site. It was used in the 1950s to refine the materials used in nuclear weapons, but now operates as a nuclear-waste storage facility.
Fidelity & fecundity
Almost half of Wood Duck females returned to the same nest box at the Savannah River Site year after year. Hepp and his colleagues paddled canoes, guided motorized flat-bottom boats, or waded through the backwater streams and forested wetlands to regularly monitor their nest-boxes. Each was about the size of a microwave oven with a top or side door that was opened to check on the hens, their eggs and whether chicks had departed successfully.
Studies of albatrosses and other seabirds, as well as many other bird species have shown that larger, healthier and older females tend to be the most successful parents. However, the dramatically different results of 1,129 occupied Wood Duck nest-boxes are consistent with a few other studies that show that a small portion of a species’ population can be important to its growth and persistence.
Wood Ducks are cavity-nesters in forests near waterways in much of the U.S. and southern Canada. Massive clear-cutting of U.S. forests and overhunting a century ago had decimated them as well as other cavity-nesting Hooded Mergansers and Common Goldeneyes.
These ducks don’t excavate cavities in large beech, sugar maple, blackgum and other deciduous trees. Instead they use natural cavities in those trees that are created when limbs die and fall off. Holes excavated by large woodpeckers also are used.
Of course not all Wood Ducks successfully raise young. The females that fail to hatch their eggs often disperse to new breeding sites. However the super moms stay. They show a high degree of fidelity year after year to the same nesting areas and even the same nest-boxes. In some years, about 20 percent of the super moms raise a second brood.
All Wood Ducks are benefiting from the partial recovery of forests and forested wetlands. A lot of that habitat has been purchased and rehabilitated thanks to the sale of Federal Duck Stamps, each of which cost $25 and is required by all waterfowl hunters. In 2015, stamp sales were more than $75 million. Since 1934, more than 5.7 million acres of waterfowl habitat was purchased with Duck Stamp revenue. Still, Wood Ducks will never be as abundant as they were before the extensive drainage of timbered bottomlands and swamps.
Much of the recently acquired and protected habitat is open to hunting. Roughly 1 million Wood Ducks are “harvested” annually by U.S. hunters. Wood Ducks usually are the top species killed in many states, particularly in those that allow special early hunting seasons that target Wood Ducks: Virginia, Tennessee, North and South Carolina, Georgia and Florida.
Hepp and his colleagues favor more research that examines qualities of individual Wood Ducks and individuals of other wildlife species. Hepp said the findings can be used by managers to make better conservation decisions.
Killing ‘super moms’
For example, the remaining states with early hunting seasons in early September penalized Wood Ducks in a perverse way. They must remain on their home territories longer, and their new flight feathers come in late – just as early season hunters arrive.
A study in the Journal of Wildlife Management found that 4 of 25 of late-molting Wood Duck females in north-central Minnesota were killed by hunters during early seasons. By that time, the non-brood females have already molted new feathers and disperse to safer areas: only 1 of 20 of them was killed.
“Female Wood Ducks breeding in northern areas are extremely susceptible to hunting during early seasons that open before the onset of migration,” states the 1992 Waterfowl Management Handbook.
Sparing Wood Duck ‘super moms’
Since that handbook was published, all northern states abolished early hunting seasons for Wood Ducks. The new study in The Auk indicates that successfully breeding female Wood Ducks in southern states are just as susceptible to early hunting as females in the North