Canvasbacks are a species of diving duck found primarily in North America. They breed in the Prairie Pothole Region of the northern Great Plains and western Canada during the summer, and migrate south to winter along the Atlantic and Pacific coasts. Their preferred habitat is large, shallow lakes and marshes with abundant aquatic vegetation. Let’s take a closer look at where canvasbacks are most commonly found throughout their annual cycle.
Breeding Range
During the spring and summer breeding season, canvasbacks are most abundant in the Prairie Pothole Region (PPR) of the northern Great Plains. This area encompasses parts of Alberta, Saskatchewan, Manitoba, Montana, North Dakota, South Dakota, and Minnesota. The PPR contains millions of small wetlands, ponds, and lakes formed by glaciers during the last ice age. These wetlands provide ideal nesting and brood-rearing habitat for canvasbacks and other prairie-nesting waterfowl.
Some of the most important canvasback breeding areas in the PPR include:
- The aspen parklands of central Alberta and Saskatchewan
- Southern Manitoba around lakes such as Lake Manitoba and Delta Marsh
- North Dakota, especially the Missouri Coteau and prairie lands north and east of the Missouri River
- Northeastern Montana
- Northern and western Minnesota
During comprehensive surveys in the 1950s-1970s, over 75% of the continental canvasback population nested in PPR habitat. More recently, numbers have declined somewhat, but the PPR remains the center of abundance for breeding canvasbacks. Ideal canvasback breeding wetlands are fairly large and shallow, with abundant submerged aquatic plants for food. Some key nesting areas include the marshes around lakes such as Pakowki Lake in Alberta.
Wintering Range
After breeding, canvasbacks migrate south to wintering areas along the Atlantic and Pacific coasts. Major wintering areas include:
- Chesapeake Bay
- North Carolina coastal marshes
- Florida Gulf Coast
- Coastal Louisiana
- Central Valley of California
- San Francisco Bay
Chesapeake Bay in Maryland and Virginia used to be the center of abundance for wintering canvasbacks, supporting over 250,000 birds in the 1970s. Due to habitat loss, numbers there have declined to around 30,000 in recent surveys. The Central Valley of California now supports the largest wintering population, with about 540,000 canvasbacks recorded in the 2019 midwinter survey.
On the Pacific Coast, canvasbacks concentrate at large estuaries like San Francisco Bay and in the Sacramento-San Joaquin River Delta. In the Atlantic flyway, they frequent shallow bays, coastal marshes, and inland reservoirs and river impoundments with abundant submerged vegetation. Mild winters allow them to winter as far south as Mexico.
Migration Stopover Habitat
During spring and fall migration, canvasbacks rely on key wetland stopover sites to rest and feed. Important migration habitats include:
- Prairie lakes and wetlands in the U.S. Prairie Pothole Region
- The Great Salt Lake in Utah
- Riverine lakes of the Mississippi River Valley
- Coastal marshes of the U.S. Gulf Coast
The abundance of food in these migration stopover habitats allows canvasbacks to rebuild energy reserves and continue their long-distance journeys between breeding and wintering grounds. For example, epicenter of canvasback migration in North America occurs at massive wetland complexes like the Bear River Migratory Bird Refuge on the northeast arm of Great Salt Lake, where up to half a million canvasbacks have been recorded in fall.
Year-round Range
There are a few parts of North America where canvasbacks can be found year-round because conditions allow them to both breed and winter in the same region:
- Central Valley of California – Sacramento Valley and San Joaquin Valley
- Western Oregon – Willamette Valley
- Southwestern British Columbia
- Puget Sound in Washington
These regions have a mild climate, productive wetlands that provide breeding habitat, and large bays or estuaries that provide wintering grounds relatively close together. For example, canvasbacks can nest in marshes around Upper Klamath Lake in southern Oregon during summer, then migrate just a few hundred miles north to the Puget Sound estuaries in Washington for winter.
Population Status and Threats
It is estimated that there are about 500,000-700,000 canvasbacks in North America. Their numbers declined in the 1970s-1980s due to drought, wetland drainage, and contamination issues, but have rebounded somewhat with improved habitat conditions. Canvasbacks are classified as a species of Least Concern by the IUCN Red List.
Some ongoing threats to canvasback populations include:
- Wetland habitat loss and degradation, especially of breeding marshes
- Drought conditions reducing breeding ponds in the Prairie Pothole Region
- Contaminants like selenium accumulating in wintering and migration habitats
- Disturbance from human recreation
Careful monitoring and conservation action to protect key wetland habitats across North America is important for maintaining healthy canvasback populations into the future.
Conclusion
In summary, canvasbacks have a broad range across North America. The Prairie Pothole Region remains the centerpiece of abundance for breeding canvasbacks. Major wintering grounds are found along the Atlantic and Pacific coasts, especially Chesapeake Bay and California’s Central Valley historically. Critical migration habitats allow canvasbacks to move between breeding and wintering areas. Careful habitat conservation efforts are necessary to preserve wetland ecosystems for canvasbacks throughout their annual cycle.
