Greater Yellowlegs (Tringa melanoleuca)

Photo by Eric PrestonGreater Yellowlegs by Eric Preston

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 100,000 (Morrison et al. 2006).

Life History

Habitat Selection

The Greater Yellowlegs breeds in wet meadows, muskegs, bogs, and similar openings within coniferous forests of the boreal forest zone. In Wisconsin it is a fairly common migrant in a wide variety of wetland habitats, including mudflats at the edges of lakes and ponds, shallow marshes, river banks, swamps, and rainwater pools (Robbins et al. 1991, Elphick and Tibbits 1998). 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). Many 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. Agricultural fields that are shallowly flooded during migration also can provide excellent resources for shorebirds and many waterfowl species (Eldridge et al. 1992).

Habitat Availability

Although the Greater Yellowlegs 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 Greater Yellowlegs and other migrant shorebirds include: Horicon Marsh, Mead Wildlife Area, Seagull Bar, Crex Meadows, and Long Island-Chequamegon Bay.

Population Concerns

Greater Yellowlegs populations experienced precipitous declines during the market hunting era but have recovered after regulatory protection was established in 1918 by the Migratory Bird Treaty Act (Elphick and Tibbits 1998). Today, the global population estimate for this species is 100,000 (Morrison et al. 2006). In general, there is a dearth of information on migrant shorebirds in North America, and no broad-scale projects currently exist that identify population sizes or monitor population changes for North American shorebird species (Brown et al. 2001). Several factors complicate population trend monitoring for Greater Yellowlegs, including their use of ephemeral wetland habitats, low densities dispersed over many sites, and the difficulty in distinguishing Greater and Lesser Yellowlegs (Brown et al. 2001, Morrison et al. 2001). Factors limiting populations of Greater Yellowlegs and other shorebirds are unknown (Elphick and Tibbits 1998, Brown et al. 2001), although ongoing broad-scale habitat alteration and land use changes likely are significant threats (Szalay et al. 2000).

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 the Greater Yellowlegs (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).

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, long-term studies of known Greater Yellowlegs individuals would advance our knowledge in all aspects of their breeding biology, including reproductive success, dispersal strategies, and territory size (Elphick and Tibbits 1998).

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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