Dunlin (Calidris alpina)

Photo by Dennis MaluegDunlin by Dennis Malueg


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 1,525,000 (Morrison et al. 2006).

Life History

Habitat Selection

The Dunlin breeds in moist-wet arctic and subarctic tundra and wet sedge marshes. In Wisconsin it is a fairly common to common migrant in a wide variety of wetland habitats, including mudflats at the edges of lakes and ponds, flooded agricultural fields, shallow marshes, and seasonal wetlands (Robbins 1991, Warnock and Gill 1996). Both managed and unmanaged wetlands are used; however, precipitation directly influences the suitability of unmanaged wetlands from year to year (Szalay et al. 2000). Habitat characteristics of stopover sites include shallow water interspersed with sparsely vegetated mudflat areas, undisturbed resting areas, and abundant invertebrate food resources (Colwell and Oring 1988, Davis and Smith 1998, Szalay et al. 2000). Migrant shorebirds are largely dependent on chironomid midge larvae and other invertebrates during migration, and the combination of shallow water and mudflats provides good conditions for these larvae and invertebrates to develop (Eldridge et al. 1992).

Habitat Availability

Although Dunlin 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 dredging and diking of rivers 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). Man-made impoundments, such as sewage ponds and stock ponds, often provide stable food resources as do wildlife refuges and other state protected lands. Important stopover areas in Wisconsin that consistently harbor concentrations of Dunlin and other migrant shorebirds include: Horicon Marsh, Mead Wildlife Area, Seagull Bar, Crex Meadows, and Long Island-Chequamegon Bay.

Population Concerns

Brown et al. (2001) estimated 1.5 million as the North American population of Dunlin and more than 3.9 million as the global population. Although population declines are suspected (USSCP 2004), trend data are generally inconclusive because no broad-scale projects exist that monitor population changes in North American shorebird species (Brown et al. 2001). Several factors complicate population trend monitoring for Dunlin, including their use of ephemeral wetland habitats, the difficulty in distinguishing species in large flocks, and a lack of information on turnover rates which confounds interpretation of migration surveys (Brown et al. 2001, Morrison et al. 2001). Factors limiting Dunlin and other shorebird populations are unknown (Brown et al. 2001), although ongoing broad-scale habitat alteration and land use changes on the wintering grounds likely are significant threats (Szalay et al. 2000, Warnock and Gill 1996).

Recommended Management

Managed wetland systems should be designed to perpetuate the natural fluctuations in water level that drive dynamic processes and provide high quality habitat for a wide diversity of wetland species, including Dunlin (Brown et al. 2001). Disking and flooding, control of invasive wetland plants and periodic, slow drawdowns can provide the mosaic of mudflats and shallow water preferred by 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. By diversifying the timing, depth, and duration of drawdowns or flooding within a wetland complex, managers can provide habitats for migrant shorebirds without decreasing their value to other avian groups with different needs (Szalay et al. 2000). In fact, because many waterfowl hens and broods consume some of the same invertebrate species, habitat management for shorebirds also can benefit waterfowl (Eldridge 1992).

To provide spring stopover habitat, Helmers (1992) recommended fall flooding approximately one month before the first heavy frost and continued maintenance of flooded conditions. During the spring migratory period (late March to late May), managed wetlands should be drawn down slowly (2-3 cm per week). During the fall migratory period (July to October), slow drawdowns should occur on flooded units and dry units should be shallowly flooded 2-3 weeks prior to this period. Units that remained dry during the summer may need to be shallowly disked prior to flooding to provide an adequate substrate for invertebrate prey (Eldridge 1992).

Minimizing factors that compromise invertebrate populations, such as habitat loss and degradation, also 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 (Knapp 2001). Conservation and management strategies for this species should be focused in the following Wisconsin ecological landscapes: Central Lake Michigan Coastal, Northern Lake Michigan Coastal, Southeast Glacial Plains, Southern Lake Michigan Coastal, and Superior Coastal Plain (WDNR 2005).

Research Needs

Although research needs for Greater Yellowlegs and most other shorebird species are significant, of primary importance is the identification of population limiting factors. 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, basic data on the energetics of Dunlin and their susceptibility to various toxins are lacking (Warnock and Gill 1996).

Information Sources


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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