By John M. Coluccy, Ph.D.
The mallard is far and away North America's most abundant duck, and this highly adaptable species is found year-round throughout almost the entire continental United States. Historical accounts suggest that breeding mallards were once rare in eastern North America, although they were common seasonal visitors along the Atlantic coast during migration and winter. Today, nearly 1 million mallards breed in the northeastern United States and eastern Canada, but surveys indicate that this population has been declining in recent years.
How did mallards gain a foothold in the East? During the 20th century, millions of captive-reared mallards were released in eastern states to supplement wild populations. Coupled with changes in habitat conditions caused by farming and urbanization, breeding mallards became well established from the mid-Atlantic states north to New England and across much of eastern Canada. Recent advances in genetic techniques have confirmed that eastern mallards are more closely related to Old World mallards (the source of captive-reared stock) than are their counterparts in other flyways.
The Status of Mallard Populations Overall, continental mallard populations have been doing well. In 2017, breeding mallards in the traditional survey area (including the Prairie Pothole Region, Western Boreal Forest, and other breeding areas) numbered 10.5 million birds (a level 34 percent above the long-term average), and have been trending upward over the long term. Mallards are counted separately in the eastern survey area (encompassing eastern Canada and parts of Maine) and in the northeastern United States from Virginia to New Hampshire. Over the past 20 years, this population—which numbered just under 900,000 birds in 2017—has been gradually declining at a rate of about 1 percent per year. While breeding mallard numbers have been largely stable in eastern Canada, they have decreased by about 38 percent in the northeastern United States. Data from the independent Breeding Bird Survey also suggest that breeding mallards have been declining in this region.
If mallards are doing so well continentally, why should we be concerned about the status of the eastern population? To answer this question, we must examine how source populations contribute to the mallard harvest in different areas. This is accomplished by calculating harvest derivation using data from mallards banded on specific breeding areas, band recovery data from mallards harvested in different states, and breeding population data. In the northeastern United States, an estimated 79 percent of the mallards harvested by hunters are produced in that region. In Pennsylvania, 75 percent of harvested mallards are raised in the state, while in New York, 69 percent of harvested mallards are homegrown. As you move south in the Atlantic Flyway, the proportion of locally raised mallards in the harvest decreases. For example, in the mid-Atlantic region only 39 percent of harvested mallards are produced locally, although 72 percent are derived from the eastern mallard population.
Why Are Eastern Mallards Declining?
Waterfowl managers are not sure what has caused the decline of the eastern mallard population. There are many theories, including the loss and degradation of breeding and nonbreeding habitat, lower survival and fitness caused by winter food shortages, and the adverse effects of hybridization between wild birds and released game-farm mallards. But none of these hypotheses have been formally tested.
The size of the annual mallard breeding population is largely influenced by two factors: adult survival and production of young. The long-term decline in eastern mallards suggests that there is a problem with either survival or production, or perhaps both. However, survival estimates from banding data have changed little since the 1990s, when the population was stable. Over the same period, estimates of mallard production obtained by the U.S. Fish and Wildlife Service (USFWS) Parts Collection Survey have not decreased either. This suggests that there might be an issue with the accuracy of one or both of these data sources.
Proposed Changes to Hunting Regulations
Since 2000, the status of the eastern mallard population has been used to set hunting seasons and bag limits for ducks in the Atlantic Flyway. Given that mallards make up only 20 percent or less of the total duck harvest in the flyway, this is no longer considered an optimal strategy. As a result, the Atlantic Flyway Council and USFWS have developed a new approach to harvest management based on the status of four other common species (wood ducks, American green-winged teal, ring-necked ducks, and common goldeneyes). Moving forward, hunting regulations for eastern mallards will be developed like other species that are currently below their population objectives, such as northern pintails and scaup. Based on our current understanding of eastern mallard population dynamics, recent harvest rates for these birds may no longer be sustainable. Consequently, waterfowl managers have recommended a reduction in the mallard bag limit from four birds to two (in the Atlantic Flyway only), beginning in the 2019–2020 waterfowl season. Hen restrictions within the two-bird mallard limit are still being considered. Managers are hopeful that a bag-limit reduction will stabilize the eastern mallard population while a new harvest strategy is developed using the best available science.
Final decisions regarding the change in the mallard bag limit and a new multispecies harvest management approach will be made this fall. The Atlantic Flyway Council will make a final recommendation to the Service Regulations Committee following their September meeting. The USFWS will then make a recommendation to the assistant secretary of the U.S. Department of the Interior, who makes the final decision on the regulations. (See "How the Seasons Are Set" on page 48 of the printed magazine for more information about this process.)
Assisting the Recovery of Eastern Mallards
A crucial first step toward the recovery of the eastern mallard population is evaluating potential bias in banding and Parts Collection Survey data to help pinpoint the cause or causes of the decline. Specific research can then be conducted to evaluate what's potentially impacting survival or production. If research shows that habitat loss is significantly influencing the decline of eastern mallards, DU will work with our state and federal partners to develop conservation strategies to help stabilize and increase the population.
Dr. John Coluccy is director of conservation planning in DU's Great Lakes/Atlantic Region.