Conservation and Management

Shooting And Trapping

Commonly hunted in the 1800s; 10–90 killed in single shots (Bent 1927). C. a. pacifica and C. a. hudsonia no longer hunted. Wintering Dunlin apparently still hunted in China (W. Tianhou pers. comm.). At The Solent, England, increases in numbers of Dunlin since the 1950s attributed to a decrease in hunting pressure (Tubbs and Tubbs 1992).

Pesticides And Other Contaminants/Toxics

Pesticide and other contaminant levels available for Dunlin, but interpretation of results difficult since no experimental work on the effects of these toxins on either breeding or migrating/wintering birds has been done.

Mean DDE concentrations from birds collected in Washington (1975–1985) from 2 different studies ranged from 0.02 to 0.85 parts per million (ppm wet weight; Schick et al. 1987, Custer and Myers 1990); higher mean concentrations found in California (1.2–7.0 ppm; Custer and Myers 1990) and Texas (3.15 ppm; White et al. 1980). Effects of these concentrations on Dunlin unknown, but falcons feeding on these birds could experience significant eggshell thinning (Custer and Myers 1990). In Washington, 1978–1981, DDE concentrations in Dunlin declined (Schick et al. 1987). Sources of contamination unclear.

Mean concentrations of selenium (dry weight, in liver) in birds from California and Washington ranged from 7.0 to 20.2 ppm at sites; these levels within the range of background levels for waterbirds (Custer and Myers 1990). In Europe, levels of selenium in migrating adult Dunlin (17–37 ppm) significantly higher than levels in birds on freshwater breeding grounds (6–8 ppm); no negative reproductive effects of selenium suspected (Goede et al. 1989).

Mean concentrations of mercury (dry weight, in liver) in Washington ranged from 4.2 to 4.4 ppm, in California from 5.5 to 18.9 ppm; concentrations high enough that sublethal effects could occur (Custer and Myers 1990).

Warnock and Schwarzbach (1995) documented strychnine poisoning of 36 Dunlin that ingested poisoned grain; mean (± SD) actual unabsorbed strychnine concentration per amount stomach content for 5 Dunlin: 110 (± 108) (µg/g).

Ingestion Of Plastics, Lead, Etc

Five of 54 Dunlin examined at the Fraser River Delta, British Columbia, had lead shot present in gizzard; consequence of ingestion unknown (Kaiser et al. 1986).

Collisions With Objects

In Europe, Dunlin occasionally collide with lighthouses, usually during storms or at night (NDW).

Degradation Of Habitat: Breeding And Wintering

Relatively little breeding habitat has been disturbed in North America; breeding areas are sparsely inhabited by humans, although some local habitat loss occurs around developments. Meehan (1986, pers. comm.) found that development in Prudhoe Bay, AK, resulted in reduction in Dunlin densities within local areas.

Loss of habitat most severe on wintering grounds. C. a. pacifica wintering habitat reduced by 30–91%; species given a habitat vulnerability score of 7 (range 3–18, 3 = lowest, 18 = highest; Page and Gill 1994).

Disturbance At Nest And Roost Sites

Trampling of nests by caribou (Rangifer tarandus) occasional source of nest loss in n. Alaska (D. Troy pers. comm.). Trampling by domestic animals destroyed 11% of nests at one breeding site in Sweden (Jönsson 1991). Winter roost flocks, especially in urban areas where roost sites are limited, are sensitive to disturbance (Warnock et al. 1995). In Europe, flush distance of migrating Dunlin from walking people: 71 m (range 57–86 m) to 163 m (range 100–300 m) (Smit and Vasser 1993).

Research Impacts

Captive birds may lose up to 14% of body mass within first 2 h of capture (Warnock 1994); decrease in pectoral muscle mass may occur after 4 h (Davidson 1984). Adult Dunlin have lower survival probability in first year of capture than in subsequent years when not captured (Warnock 1994). Color-dyed birds susceptible to greater predation by Parasitic Jaegers, Glaucous Gulls, and Glaucous-winged Gulls (Larus glaucenscens) if not held until oils preened into feathers (REG). Radio-marked birds suffer greatest predation within 4 d of capture (Warnock 1994). Trapping at nest the previous year not shown to affect likelihood of dispersal (Jackson 1994).

Measures Proposed And Taken

Western Hemisphere populations are protected by the North American Migratory Bird Treaty Act of 1918. One of 3 species of shorebirds listed by the Conservation of Arctic Flora and Fauna as “indicator” species for assessing health of holarctic ecosystems. Several major sites used by North American populations have been included in the Western Hemisphere Shorebird Reserve Network (San Francisco Bay, CA; Grays Harbor, WA; Copper River Delta, AK; Delaware Bay) (Gill et al. 1994, Morrison et al. 1994, B. Harrington pers. comm.).

Active management practices limited. Rehfisch (1994) found that manipulating water depth in human-made lagoons increased benthic invertebrate biomass (mainly Chironomidae) and that vegetation-free embankments enhanced predator detection by shorebirds.

Effectiveness Of Measures: The Species’ Response

There is concern by those most familiar with the species that populations have declined continentwide. Absence of rangewide population monitoring program (but see Morrison et al. 1994) prevents reliable assessment of population status and trend.