Wilson’s Phalarope (Phalaropus tricolor)

Wilson's Phalarope by Jack BartholmaiWilson's Phalarope distribution map

Status/Protection

Population Information

There are currently no broad-scale projects designed to identify population size or monitor changes within shorebird populations (Brown et al. 2001). The North American population estimate is 1.5 million (Morrison et al. 2006).

Life History

Habitat Selection

Although there are Wisconsin breeding records for the Wilson’s Phalarope (Robbins 1991, Harriman 2006), the state is not within its core nesting area. Throughout its range, it nests in a variety of habitat types and conditions, including upland and wetland areas containing both sparse and dense vegetation (Colwell and Jehl 1994). In Wisconsin it nests in uncropped fields, agricultural fields, sedge meadows, and other open lowland habitats (Harriman 2006). During migration it prefers open, shallow water habitats, particularly saline and alkaline lakes in the western portion of its range (Colwell and Jehl 1994).  

Habitat Availability

Although the Wilson’s Phalarope and other shorebirds are opportunistic and can capitalize on food resources wherever available during migration, the loss of wetlands, tiling and draining of agricultural fields, and conversion of grassland habitats has reduced foraging opportunities in Wisconsin. 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% (2.1 million hectares) of these wetland habitats remain (WDNR 2003) and conditions at these sites can be extremely variable and highly dependent on precipitation and hydrology patterns (Szalay et al. 2000). Furthermore, exotic species (e.g., purple loosestrife, zebra mussel, carp) and industrial effluents have the potential to reduce invertebrate food resources at these sites (WDNR 2005). The conversion of pastures and other short-grass habitats to row crops also reduces foraging habitat in the state. Of the 850,000 hectares of native prairie present prior to Euro-American settlement, less than 4,000 hectares remain today (WDNR 2005).

Population Concerns

The North American population estimate is 1.5 million with a declining trend suspected (USSCP 2004, Morrison et al. 2006). In general, population trend data are inconclusive because no broad-scale projects currently exist that monitor changes in North American shorebird populations (Brown et al. 2001). Several factors complicate population trend monitoring for the Wilson’s Phalarope, including its use of ephemeral wetland habitats and a lack of information on turnover rates at migratory stopover sites which confounds interpretation of survey data (Brown et al. 2001, Morrison et al. 2001). Limiting factors are unknown (Brown et al. 2001), although ongoing broad-scale habitat alteration and land use changes likely are significant threats (Szalay et al. 2000, Colwell and Jehl 1994).

Recommended Management

Preventing habitat destruction and minimizing factors that compromise the maintenance of invertebrate populations are important management considerations. The continuation of wetland management, protection, and restoration efforts such as the Wetlands Reserve Program, Partners for Fish and Wildlife, and North American Wetland Conservation Act will benefit this and other waterbird species. Wetland restoration efforts should create complexes of seasonal and semipermanent wetlands within areas that will increase overall wetland connectivity (Knapp 2001). Management actions (e.g., disking and flooding, control of invasive wetland plants, periodic, slow drawdown) that create mosaics of mudflats and shallow water areas will provide foraging habitat for Wilson’s Phalarope and other migrant shorebirds (Eldridge 1992). Managed wetland drawdowns should coincide with shorebird migration but should be staggered across units to extend habitat and food resource availability throughout the entire migratory period (Helmers 1992). Partnerships between state and federal agencies and private organizations dedicated to the restoration, conservation, and management of grassland ecosystems also will benefit the long-term management of Wilson’s Phalarope and other grassland-associated species. Conservation and management efforts for this species should be focused in the following Wisconsin ecological landscapes: Central Lake Michigan Coastal, Central Sand Plains, Northwest Sands, and Southeast Glacial Plains (WDNR 2005).

Research Needs

Although research needs for Wilson’s Phalaropes and most other shorebird species are significant, of primary importance is the identification of population limiting factors (Brown et al. 2001). This information is essential to better understand which factors need to be changed to increase shorebird populations. Improved survey methods and an institutional capacity for monitoring shorebirds also are urgently needed (Brown et al. 2001). A state assessment of the distribution, abundance, conditions, and ownership of wetlands and other important shorebird habitats also would further management efforts and guide future restoration projects (Szalay et al. 2000). More information on the dynamics of migration patterns is warranted, including how populations move among sites and why (Brown et al. 2001). In Wisconsin, comparative studies on the feeding ecologies of migrant shorebirds would help determine how coexisting species and their prey react to different wetland management regimes and habitat conditions. Color-banding individuals at stopover sites may help to determine length of stay, refueling capacity, impacts of disturbance, and important habitat features associated with these sites (Davis and Smith 1998, Szalay et al. 2000, Brown et al. 2001). Finally, studies that document Wilson’s Phalarope survivorship and lifetime reproductive success are warranted (Colwell and Jehl 1994).

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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