The black-necked stilt (Himantopus mexicanus) is a locally abundant shorebird of western North America. It is a long-legged, black and white wader in the avocet and stilt family Recurvirostridae. Stilts and avocets together make up the suborder Charadrii. It is found in a variety of wetland habitats, both coastal and inland. It feeds by probing in shallow water or on soft mud. The black-necked stilt is a migratory species, breeding in North America and wintering from the southern United States south through Central America and the Caribbean to northern South America.
What is a black-necked stilt?
The black-necked stilt is a graceful, long-legged shorebird named for its distinctive black neck and head. Adults have black backs, white underparts, and long pink legs. Their black bills are slightly upturned. Males and females look alike, and juveniles resemble adults in nonbreeding plumage.
Black-necked stilts are found in marshes, mudflats, shorelines, and agricultural wetlands across western and southern North America. They get their food by wading in shallow water and probing or pecking for insects, crustaceans, fish and plant material.
These shorebirds are agile fliers with narrow, pointed wings. They are known for their aerial courtship displays. When disturbed, black-necked stilts may take flight with their long legs trailing behind.
What is their range?
The breeding range of the black-necked stilt extends from southern British Columbia through the western United States to northwestern Mexico. It is also found locally across the southern tier of states from California to the Carolinas.
Small populations breed in the Caribbean in Cuba, Jamaica, Hispaniola, and Puerto Rico. In South America, breeding populations are found in coastal regions from Colombia and Venezuela south to Chile and central Argentina.
During the nonbreeding season, black-necked stilts withdraw from the northern parts of their range. They winter from Baja California, southern Arizona, and the Gulf Coast south through Mexico and Central America to northern South America.
Migration Patterns
North American migration
The migration patterns of black-necked stilts in North America can be summarized as follows:
- Northern populations are migratory, moving south for the winter.
- Birds breeding in Canada and the northern U.S. migrate to the southern U.S. and Mexico.
- Stilts that nest in California, the Southwest, and Gulf Coast are generally year-round residents.
- Migration peaks from August to September and again in April.
- Young birds tend to migrate earlier in the fall than adults.
Migration distance depends on the breeding location. Stilts that nest farther north travel longer distances of up to a few thousand miles between breeding and wintering areas. Birds in the south may migrate only short distances or not at all.
Banding studies show that black-necked stilts exhibit site fidelity, returning to the same breeding and wintering sites year after year. Their migratory routes and stopover sites are also consistent between years.
South American migration
In South America, black-necked stilts breed in southern coastal regions during the austral spring and summer from September to February. After breeding, they migrate northward to wintering areas.
Birds breeding in southern Chile and Argentina migrate north along the Pacific coast to winter in northern Chile and southwestern Peru.
On the Atlantic side, stilts winter in northern Brazil and the Guianas after breeding farther south in Argentina, Uruguay, and southern Brazil. Movement patterns between breeding and wintering grounds are not well studied.
Wintering Range and Habitats
The winter range of the black-necked stilt extends along the Pacific coast from southern California to Peru and on the Atlantic side from the southeastern U.S. to northern South America.
Winter habitats
Typical wintering habitats include:
- Coastal salt flats, lagoons, estuaries
- Freshwater lakes, ponds, wetlands
- Flooded agricultural fields
- Irrigation canals and ditches
- Salt evaporation ponds
Wintering black-necked stilts are strongly associated with shallow aquatic habitats, both tidal and non-tidal. They forage in very shallow water or soft mud substrates.
Coastal populations winter in estuaries, salt marshes, tidal flats, and beaches. Inland stilts are found around lakes, rivers, streams, wastewater ponds, and flooded agricultural land.
Geographic distribution
On the Pacific Coast, black-necked stilts winter from San Francisco Bay south through coastal California and along the Baja Peninsula. Other significant wintering areas are the Gulf of California, west coast of Mexico, and coastal wetlands of Guatemala, El Salvador, and south to Peru.
In the interior, they winter around wetlands, reservoirs and agricultural areas from southern Arizona and New Mexico south into Mexico.
Along the Gulf Coast and Atlantic seaboard, wintering areas extend from coastal Texas to Florida and the Caribbean. Inland stilts occur south throughout the Mississippi Valley.
Farther south, major concentrations are found around Lake Maracaibo and Gulf of Venezuela, the Guianas, northeastern Brazil, Amazon basin wetlands, and the Pantanal.
Threats and Conservation
The black-necked stilt has a large range and populations appear stable. However it does face a number of threats on its breeding and wintering grounds.
Habitat loss
Draining of wetlands for development and agriculture has caused habitat loss throughout the stilt’s range. For example, more than 90% of California’s Central Valley wetlands have been converted to farms and cities.
Coastal habitat is threatened by changes such as sea level rise, erosion, tidal flats conversion for development, and reduced flows into estuaries.
Disturbance
Black-necked stilts are sensitive to human disturbance and will abandon nests if frequently flushed by recreationists, vehicles, or pets. Disturbance may be a problem near urban wetlands.
Water management
Water diversion and channelization have altered wetland ecosystems and salinity levels in key wintering sites like San Francisco Bay. Dams and river management impact inland wetlands.
Irrigation runoff can degrade water quality. Some stilts are poisoned feeding around agricultural wastewater ponds contaminated with pesticides and selenium.
Oil pollution
Black-necked stilts are vulnerable to oil spills in coastal habitat, especially in refinery and shipping zones like San Francisco Bay and the Gulf of Mexico. The 2010 Deepwater Horizon spill oiled Gulf Coast wetlands used by migrating stilts.
Conservation Measures
A variety of conservation actions help protect black-necked stilt populations:
- Habitat preservation through wetland restoration and protection of key breeding and wintering sites
- Altering water management to benefit wetlands
- Restricting human access near nesting colonies
- Maintaining upland buffers around wetlands
- Reducing contamination from agricultural runoff
International agreements like the Western Hemisphere Shorebird Reserve Network identify and protect critical shorebird habitats. State and local partnerships also aim to conserve wetlands for nesting and migrating stilts.
More research is needed on migration routes, connectivity between sites, and habitat needs during the annual cycle to inform full life cycle conservation.
Conclusion
The black-necked stilt is a migratory shorebird that breeds across western North America and winters along the Pacific and Atlantic coasts from the southern U.S. to South America.
Northern populations migrate thousands of miles between breeding and wintering wetlands. Southern stilts may only make short local movements.
Coastal and inland wetlands provide important wintering habitat. Conservation of these sites, which face threats from development, disturbance, and altered hydrology, is vital for maintaining stilt populations.