Canvasback (Aythya valisineria)

Photo by Thomas SchultzCanvasback by Thomas Schultz

Status/Protection

Population Information

The Federal BBS information can be obtained at http://www.mbr-pwrc.usgs.gov/bbs/bbs.html by clicking on Trend Estimates and selecting the species in question. All estimates are for time period (1966-2005).

Life History

Habitat Selection

Although there are Wisconsin breeding records for Canvasbacks (Bellrose 1976, Robbins 1991, Mowbray 2002), the state does not sustain a regular breeding population. However, Wisconsin is an important location for Canvasback migration. During fall migration, Canvasbacks use large, open-water areas including impounded portions of slow-moving rivers, lakes, and open marshes (Kahl 1991, Mowbray 2002). Canvasbacks tend to use most of the same stopover sites during spring migration but are more widely dispersed (Mowbray 2002). Optimal habitats provide both refuge from disturbance and abundant food resources such as sago pondweed, stiff arrowhead, and winter buds and tubers of wild celery (Kahl 1991, Mowbray 2002). Snails and small clams have become increasingly important food items where dense beds of macrophytes are lacking (Kahl 1991). Scattered individuals and small flocks often remain to winter in open water areas of Wisconsin (Robbins 1991). Winter habitat use is influenced by weather conditions, changes in habitat conditions, and human disturbance (Mowbray 2002).

Habitat Availability

The most important Wisconsin sites for migrating Canvasbacks during the past century were the Upper Mississippi River (UMR) pools 7-9 and the shallow inland lakes of the southeastern and southcentral regions (Jahn and Hunt 1964, Bellrose 1976, Kahl 1991, Robbins 1991). In recent years, many of the inland lakes have suffered from fluctuating water levels, proliferation of carp and other invasive species, increased sedimentation, and eutrophication, resulting in a decline of food resources. Consequently, fall Canvasback concentrations have shifted away from these traditional areas and now primarily occur at the UMR pools. Canvasbacks also occur in smaller concentrations at the St. Croix Valley, Crex Meadows, George W. Mead, Grand River Marsh, and Horicon Marsh wildlife areas, and Green Bay (Fannes 1981, Wheeler et al. 1984, WDNR 1992). Spring migrants often use ephemeral ponds in croplands and flooded sedge meadows in addition to the same fall stopover areas (J. March, pers. comm.). Many of the historically important inland lakes offer potential for restoration. Lakes Poygan, Winneconne, Butte des Morts, Koshkonong, Puckaway and Beaver Dam are large open-water areas with large littoral areas capable of supporting the dense beds of wild celery and sago pondweed required by Canvasbacks (Kahl 1991).

Population Concerns

Waterfowl Breeding Population and Habitat 2006 survey data indicate that Canvasbacks increased 33% relative to 2005 and 23% relative to the long-term average (1955-2005) (USFWS 2006a). They are not a regular breeding species in Wisconsin, but are a fairly common to common migrant (Robbins 1991). Aerial waterfowl survey data from the UMR pools consistently show concentrations of >200,000 staging Canvasbacks, with an eleven-year peak average of 261,000 (USFWS 2006b). This represents a significant portion of the continental fall population of Canvasback and is an important area for Canvasback migrating east to Chesapeake Bay.

Excessive human disturbances, such as recreational boating, can reduce the suitability of staging areas to migrating waterfowl (Korschgen et al. 1985, Kahl 1991). In response to disturbances, the Upper Mississippi River National Wildlife and Fish Refuge recently established more than 17,000 hectares of Closed Areas, which provide waterfowl the opportunity to feed and rest without disturbance during migration and at wintering locations (Kenow et al. 2003, USFWS 2006c).

Recommended Management

Due to the potential threats of disease, toxic spills, and habitat degradation along the Upper Mississippi River, the long-term health of the eastern Canvasback population is dependent on restoring alternative staging habitats (Kahl 1991, Mowbray 2002). Invasive species control, particularly carp, is critical for maintaining the suitability of existing staging areas (WDNR 2005). Managers should minimize disturbances at important Canvasback staging areas by instituting no-wake or non-motorized zones, fishing and hunting restrictions, and public awareness campaigns during spring and fall migration (Mowbray 2002; see Kenow et al. 2003). A variety of hunting regulation strategies (reduced daily bag limits, shorter seasons, and closed seasons) have been used effectively over the years to reduce Canvasback harvest during low production years. Annual changes in hunting regulations relative to changes in breeding population will continue to be adjusted to achieve appropriate harvest rates.

Research Needs

An assessment of Canvasback staging habitat needs to be conducted in Wisconsin. Water quality, invasive fish populations, toxic contaminants, human disturbances, and other factors limiting Canvasback food availability at staging areas need further study (Kahl 1991). More research is needed into methods to restore submergent aquatic beds in large shallow-water lakes (WDNR 2005). Studies are needed to relate changes in nutrient availability to changes in migration patterns, feeding strategies, and survival (Mowbray 2002).

Information Sources

References

Contact Information

Kreitinger, K., Y. Steele and A. Paulios, editors. 2013.
The Wisconsin All-bird Conservation Plan, Version 2.0. Wisconsin Bird Conservation Initiative.
Wisconsin Department of Natural Resources. Madison, WI.

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