What Has Happened to Eastern Mallards?
New Jersey Hunting
By Ted Nichols, Wildlife Biologist
What Has Happened to Eastern Mallards and How Does This Affect Atlantic Flyway Duck Seasons?
April 1994. A young New Jersey Division of Fish and Wildlife waterfowl biologist, soaked in sweat, climbs out of his kayak and tallies up the waterfowl observed on the randomly-located, 1 square-kilometer survey plot that is partially situated on a tidal freshwater marsh in Gloucester County. The tally: 23 Canada geese, four pairs of wood ducks and six pairs of mallards.
April 2019. Twenty-five years later, the same waterfowl biologist, now mostly gray-haired and 10 pounds heavier, climbs out of the same kayak, at the same survey plot, to tally the findings after completing the 2019 survey. The results: similar numbers of Canada geese and wood ducks, but only half the number of mallard pairs when compared with the 1994 survey.
I am that biologist.
A lot has changed over those years. The Internet now dominates daily activities, nearly everyone has a cell phone and the Philadelphia Eagles have (finally!) won a Super Bowl. During those 25 years in New Jersey, the resident Canada goose population grew in the 1990s, peaked in 2000 and then subsided. The wood duck population has remained stable. However, over that same time, I have witnessed a slow, chronic decline of mallards in New Jersey and the proof is in the numbers.
Mallards have declined about 40 percent since the 1990s (Figure 1, red line) in the Atlantic Flyway Breeding Waterfowl Survey which is a ground-based survey conducted each spring from New Hampshire to Virginia. A closer examination of the data reveals that the decline is not unique to New Jersey but occurring across nearly all Atlantic Flyway states and across all landscape types—rural, suburban, urban. Similarly, mallard harvest in the U.S. Atlantic Flyway has declined 40 percent since the late 1990s despite that the number of hunters has remained stable plus the duck season length and mallard bag limit has remained unchanged. Two independent surveys yield the same grim story about eastern mallards.
While mallards in the eastern U.S. have declined, mallards breeding in eastern Canada and Maine have remained stable (Figure 1, green line), fluctuating around a mean of just over a half million birds. If the U.S. population of mallards were declining while the population in Canada were simultaneously increasing, it would be easy to postulate that the breeding population was just shifting northward.
Unfortunately, that is not the case. Given that mallards in the U.S. portion of the breeding range were historically more numerous, they have more “weight” when considering the overall population trend of all mallards in eastern North America. The total population of eastern mallards has declined about 25 percent, with a rate of decline of -1.4 percent per year.
Red-hot Questions Need Answers
These circumstances lead to two burning questions:
- Since mallards are used to set duck hunting seasons, where does this decline lead us?
- What is happening to eastern mallards?
Let’s answer the first question. Annual duck hunting regulations are based on biological population assessments using the Adaptive Harvest Management (AHM) process developed cooperatively by the U.S. Fish and Wildlife Service and states agencies. Adaptive Harvest Management is an objective, science-based, regulation-setting process. For over 20 years, duck seasons in each flyway have been based on the status of the mallard population most abundant within each flyway. Mallards have been used since they are the most common species with the most survey and banding data.
Adaptive Harvest Management strives to provide maximum harvest opportunity into the future by weighing current mallard population levels and harvest while projecting future mallard population changes. As the mallard population grows, there is more harvest opportunity; if mallards decline, harvest opportunity declines as well. While eastern mallards have declined over the past 20 years, the majority of the other 20+ duck species that call the Atlantic Flyway home, have had stable populations. Consequently, eastern mallards are no longer reasonable surrogates for setting overall duck seasons in the Atlantic Flyway.
Since 2011, the Atlantic Flyway has been developing a new harvest strategy for ducks referred to as “Multi-Stock Adaptive Harvest Management” that is being implemented this year. Multi-Stock Adaptive Harvest Management considers the collective population status of American green-winged teal, wood ducks, ring-necked ducks and common goldeneyes when rendering a decision for annual regulations. These four species comprise 60 percent of the Atlantic Flyway duck harvest, represent a wide-range of species’ life histories and have expansive breeding and wintering populations distributed across the Atlantic Flyway. Multi-Stock Adaptive Harvest Management modeling considers the allowable annual harvest based on productivity and the carrying capacity of the flyway habitat for each species. For setting duck hunting regulations in the Atlantic Flyway, the switch from eastern mallard Adaptive Harvest Management to Multi-Stock Adaptive Harvest Management is a fundamental science and policy change.
Mallards will not be part of Multi-Stock Adaptive Harvest Management but will have their own harvest strategy similar to the way canvasback or pintail seasons are set. Given the decline in eastern mallard abundance, beginning in 2019, all Atlantic Flyway states will see a bag limit reduction to two mallards with no more than one hen.
Why Are Eastern Mallards Declining?
The short answer is, we do not know. There are numerous theories. Wildlife populations are primarily driven by annual survival of adults and reproduction. A long-term mallard decline suggests that one or both parameters are lagging. It is troubling that mallard banding data suggests survival rates over the past 20 years have not changed appreciably from the early 1990s when the population was stable. Further, the annual number of young birds produced, as measured in harvest surveys, also has not changed. The fact that mallards are declining, while estimates of survival and young production seem reasonable, suggests there could be a bias in one or both of the data streams.
In wildlife science, population changes are rarely driven by one issue but frequently by multiple factors, some of which may act together. Some biologists speculate that the recommended decline of winter feeding by the public (e.g. in parks), a widespread practice prior to the 1990s, may have had a subtle effect on survival or production.
Another element is that eastern mallards have a significant component of “game-farm” mallard genetics, documented with new genetic techniques, perhaps leaving these birds less fit for survival in the wild. The actual mechanism on how this “reduced fitness theory” might function is lacking.
Historically, mallards were breeding ducks of the prairies and did not occur as breeding ducks in the east until they moved here during the 1960s. These populations were bolstered by the game farm mallard releases. In the wildlife literature, there are many examples of new species “invading” or being purposefully introduced into new geographic areas. Often these new species initially thrive and grow, then decline to a lower equilibrium population. Examples include cattle egrets coming to North America from Africa in the 1950s and the reintroduction of wild turkeys in the east. Could mallards be suffering this same fate?
Although mallards have declined, they remain one of the most abundant ducks in the Atlantic Flyway. Notwithstanding, Atlantic Flyway biologists are working with federal, academic and non-government partners conducting research to identify, and hopefully resolve, factors that are limiting “greenheads” in the east. Still, I can’t help but wonder—what will New Jersey’s annual waterfowl survey show us 25 years from now?