USGS Conducts Assessment to Inform Black Duck Habitat Decisions

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Issue: The Chesapeake Bay is along the Atlantic Flyway and has over 1 million migratory birds winter each year. Black ducks are one of 30 species that depends on habitats along Chesapeake Bay for their annual migration. Managing the black duck population at time when land use and sea-level rise pose a recognized peril to this species and their habitats require a strategic approach.

The Chesapeake Bay Program recognized Black Duck could be used as an indicator species for migratory watershed included this outcome in the Chesapeake Watershed Agreement “By 2025, restore, enhance, and preserve wetland habitats that support a wintering population of 100,000 black ducks, a species representative of the health of tidal marshes across the watershed.”

USGS Study

The USGS conducted a study of factors affecting black duck populations. One of the products is a Web-based viewer on habitat vulnerability for Black Ducks and other migratory birds, based on projections of sea-level rise.

 

Key Findings

American Black Duck.  Photo by Jonathan Fiely.

American Black Duck

(Credit: Jonathan Fiely, USGS Patuxent Wildlife Research Center. Public domain.)

The USGS has released the Habitat Vulnerability Assessment for Wintering American Black Ducks.

The USGS estimated food availability among five main wetland cover types used by overwintering American Black Ducks: subtidal, fresh water, high marsh, low marsh, and mudflat. Bioenergetics models used to inform North American Waterfowl Management Plan (NAWMP) can be simplified into two major components: energetic demand and energetic supply. Energetic demand is the estimated total cost for a duck to obtain the food (i.e foraging costs, metabolic costs, etc). Energy supply (food availability) is estimated by multiplying the foraging value of each cover type (the amount of food produced in each cover type as measured by its energetic value) by the total area of each cover type. The difference between energetic supply and energetic demand can then be used to direct conservation planning and implementation, answering key questions of “what, where, and how much” habitat is needed to achieve a target carrying capacity.

 

Management Applications

The habitat vulnerability has been shared with the CBP Black Duck Action Team and Wetlands workgroup to inform their decisions for restoration and conservation of migratory bird habitat.

 

For more information

Alicia Berlin, Research Wildlife Biologist with Eastern Ecological Science Center
The Black Duck Study is part of the USGS Chesapeake theme addressing coastal habitats and waterbirds. More information can be found at the Chesapeake Bay Activities. The USGS has additional journal articles in preparation about the Black Duck study.

Posted October 5, 2021

 

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