Two black ducks captured on the western shore of Chesapeake Bay migrated north through the Great Lakes region. One bird passed through Lake St. Clair, as did the majority of black ducks captured in Ohio. Many of these birds passed through Saginaw Bay and the St. Marys River of Michigan before crossing into Ontario. Interestingly, none of the black ducks captured in Ohio crossed into the Atlantic Flyway at any time during migration.
Only 13 black ducks in the DU study provided data during the fall migration. Of these, birds nesting in Ontario and Quebec began migrating south on October 25 and arrived on their wintering areas on December 4 (on average). In contrast, black ducks breeding in Labrador departed around October 5 and arrived on their wintering areas on approximately November 18.
HOMEWARD BOUND Two female black ducks captured in Ohio provided data during both years of the DU study. Remarkably, each bird settled on the same wetland on their breeding grounds that they had used the year before. This behavior is an example of philopatry—a tendency among waterfowl to return to the same breeding area—and emphasizes the need to consider connections between breeding, migration, and wintering habitats across vast ranges. Data from these two philopatric females also suggest that black ducks may spend more time on wintering areas and less time on spring stopovers than some regional management plans assume. Below: Black ducks follow several different migration corridors between breeding and wintering areas.
Thirty-two black ducks provided data during spring migration. Average departure dates varied by state, with birds captured in New York leaving on March 28, Ohio (April 14), Virginia (April 14), Delaware (April 21), and New Jersey (May 22). The average arrival date on the breeding grounds was about two weeks earlier in the Mississippi Flyway (April 30) than in the Atlantic Flyway (May 17). This isn't that surprising given that black ducks captured in the Mississippi Flyway migrated a shorter average distance (501 miles) than those in the Atlantic Flyway (843 miles).
The number of spring stopovers made by black ducks in the DU study also varied by flyway: birds in the Atlantic Flyway stopped nearly twice as many times on average as those in the Mississippi. Although the length of time the birds spent on each stopover was nearly the same in both flyways, there was a positive relationship between the total distance the birds migrated and the number of, and total time spent on, stopovers. Simply put, black ducks in the Atlantic Flyway migrate farther, stop more, and subsequently spend more time on stopovers during migration.
When black ducks were grouped by latitude (North—New York and Ohio; South—Delaware, New Jersey, and Virginia), similar relationships persisted. One interesting finding was that southern black ducks migrated faster (by six miles per hour on average) than their northern counterparts, but still arrived on breeding areas more than two weeks later.
DU researchers also measured each black duck's body mass, which can provide a good indication of overall health. Mass was lowest among birds captured in the south and increased with latitude. Reduced energy reserves, prolonged migration, and delayed reproduction may be causing disproportionate declines among black ducks in the southern portion of their range.
While the results of this study were derived from a small subset of black ducks, the data will be used to help set habitat conservation objectives for black ducks during the nonbreeding period. DU and its partners are committed to implementing the results of this study and other research to conserve populations of black ducks and other waterfowl in North America.
Kurt Anderson is a DU biologist based in Annapolis, Maryland. Dr. John Coluccy is director of conservation planning at DU's Great Lakes/Atlantic office in Ann Arbor, Michigan.
PARTNERS IN RESEARCH DU would like to thank the following partners for their generous support for the black duck satellite tracking study: the Black Duck Joint Venture, Camp Fire Conservation Fund Inc., Cape May National Wildlife Refuge (NWR), Chincoteague NWR, Raymond and Barbara Dalio, Delaware Division of Fish and Wildlife, Edwin B. Forsythe NWR, the Herbert H. and Grace A. Dow Foundation, Moses D. Nunnally Jr. Charitable Lead Trust, New Jersey Division of Fish and Wildlife, New York State Department of Environmental Conservation, Ohio Division of Wildlife, Ottawa NWR, Prime Hook NWR, Suffolk County Department of Parks, the Nature Conservancy, the University of Delaware, Upper Mississippi River and Great Lakes Region Joint Venture, Virginia Department of Game and Inland Fisheries, Waterfowl Research Foundation Inc., the Winous Point Marsh Conservancy, and a host of other Major Sponsors.
For more information about this study and DU's Black Duck Initiative, go to www.ducks.org/conservation/black-duck-study