Redhead (Aythya americana)

Photo by Jack BartholmaiRedhead by Jack BartholmaiRedhead distribution map

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

Redheads commonly use seasonal and semi-permanent wetlands containing dense stands of cattails, bulrushes, or sedges during the breeding season. Marshes that are most suitable for breeding are characterized by an approximate 50:50 ratio of well-interspersed cover and open water areas (Woodin and Michot 2002). Female Redheads may shift from using primarily small, semi-permanent wetlands during nesting to larger, semi-permanent and seasonal wetlands with more open water for brood rearing (Yerkes 2000). Thus, a mosaic of wetland types may be important. Redheads construct over water nests in relatively tall, dense emergent vegetation (Woodin and Michot 2000). At Horicon Marsh in southeastern Wisconsin – a primary nesting area in the state- nests are built predominantly in cattail stands and occasionally on muskrat houses during high water years (Swanberg 1982, WDNR 2004). Redheads often forage at shallower depths in prairie wetlands, which may provide a richer food source and require less energy expenditure (Torrence and Butler 2006). The diet of adult and juvenile Redheads at Horicon Marsh includes tubers, seeds (Scirpus spp. and Polygonum spp.), Cladocera and Chironomidae larvae, and adult and larval Hemipterans and Dipterans (Kenow and Rusch 1996).

During spring and fall migration, Redheads use large lakes, reservoirs, and shallow river pools such as Lake Onalaska along the Upper Mississippi River near La Crosse, Wisconsin. Small numbers of Redheads are observed wintering on inland lakes and reservoirs, staying as far north as permitted by the abundance of submerged aquatic plants and seeds (Robbins 1991, Woodin and Michot 2002). 

Habitat Availability

Horicon National Wildlife Refuge (NWR) in Dodge County provides habitat for the majority of nesting Redheads in Wisconsin (WDNR 1992, Volkert 2006).  Several state wildlife areas and at least 16 Waterfowl Production Areas also harbor breeding records (Jahn and Hunt 1964, Robbins 1991) and provide important stopover areas. Redheads are common migrants in the state (Robbins 1991) and frequently use inland lakes, including Rush, Winnebago, Poygan, Winneconne, Buttes des Morts, Koshkonong, Beaver Dam, and Puckaway (Jahn and Hunt 1964, Kahl 1991, WDNR 1992). Fox Lake and Lake Maria also were major fall concentration sites in the mid-twentieth century (J. March, pers. comm.). However, poor water quality at some of these sites may impact their suitability by reducing invertebrate biomass and inhibiting emergent/submergent plant growth (Kahl 1991, WDNR 1992, Kenow and Rusch 1996). Pools 7 and 8 along the Upper Mississippi River and Green Bay and associated marshes also are important feeding and resting areas for migrating Redheads (Fannes 1981, WDNR 1992). A limited number of wintering birds are found each year in Wisconsin, primarily in the southeastern counties (Robbins 1991).

Prior to Euro-American settlement, wetlands occupied an estimated four million hectares of the total fourteen million hectares of Wisconsin’s land area. Today, 53%, or 2.1 million hectares, of these wetland habitats remain (WDNR 1995). Agricultural drainage and urban development remain threats to wetland ecosystems and local populations of wetland-associated birds. Human activities that alter hydrology and introduce invasive plant species also threaten wetland habitats (WDNR 2003). Strict wetland use regulations and incentive programs designed to restore or enhance wetlands, such as Wetland Reserve Program, have helped to curb habitat loss and protect existing wetlands (WDNR 1995). Additionally, the Upper Mississippi River/Great Lakes Region Joint Venture has protected, enhanced, or restored more than 51,000 hectares of upland habitat in Wisconsin as well as 37,000 hectares of wetland habitat.

Population Concerns

Waterfowl Breeding Population and Habitat 2006 survey data indicate that Redheads increased 55% relative to 2005 and 47% relative to the long-term average (1955-2005) (USFWS 2006). Breeding Bird Survey (BBS) data corroborate this trend, suggesting a non-significant annual increase range-wide (Sauer et al. 2005). Redheads are rarely encountered on Wisconsin BBS routes, thus state population trends are not available. Redheads are a fairly common summer resident in eastern Wisconsin according to Robbins (1991); however, breeding was confirmed in less than 1% of the surveyed quads during the Wisconsin Breeding Bird Atlas. The majority of the Atlas confirmations came from Horicon Marsh and Lake Winnebago regions (Volkert 2006).

Although Horicon Marsh attracts a significant number of breeding Redheads, recruitment is poor because of nest predation (WDNR 1992). In Wisconsin, raccoons and mink are responsible for an annual nest predation loss of 18-33%. Female Redheads in Wisconsin have intermediate levels of intraspecific parasitism, but the hatching success of parasitized and non-parasitized nests typically does not differ (Woodin and Michot 2002). Carp and other invasive exotic wetland species are a threat to the health of the aquatic ecosystems that Redheads use for breeding and migration (WDNR 2005). Strict harvest regulations have reduced the annual hunting mortality (Woodin and Michot 2002). Excessive human disturbances, such as recreational boating, can reduce the suitability of staging areas for 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 2006).

Recommended Management

Because of the apparent low invertebrate biomass available at some wetlands, managing areas for moist-soil plant seeds high in metabolizable energy, such as Leersia oryzoides, may be crucial to supplementing nutrient reserves of breeding females. Invertebrate abundance also may be enhanced through periodic drawdowns of water levels. Water drawdowns also help to control the invasive species impacting wetland systems (WDNR 2005). Management efforts that protect existing wetlands and restore drained wetlands will benefit Redheads and other wetland-associated species. Managers should provide mosaics of seasonal and semi-permanent wetlands located in close proximity. The need for a variety of wetland habitats will require a landscape approach to wetland management (Yerkes 2000). Annual changes in hunting regulations relative to changes in the continental breeding population will continue to be adjusted to achieve appropriate harvest rates.

Research Needs

The long-term effects of wetland enhancement programs on breeding Redheads should be evaluated (Woodin and Michot 2002). More research is needed into methods to restore submergent aquatic beds in large shallow-water lakes (WDNR 2005). Redhead migration ecology and winter ecology need further study. More information is needed on population dynamics, particularly estimates of survival for all stages of the annual cycle. Without these data it is difficult to focus management actions (Woodin and Michot 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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