Himantopus mexicanus
Black-necked Stilts, with their attractively patterned black and white plumages, are a striking sight as they move slowly and gracefully through shallow water on their extremely long, slender red legs, searching for aquatic invertebrates. During breeding season, these birds, highly protective of their nests and eggs, call incessantly in the presence of humans or other potential predators. Groups of these semi-colonial birds, sometimes accompanied by American Avocets (Recurvirostra americana), also dive at predators, and feign mortal injuries (Robinson et al. 1999).
Two favored breeding areas, salt water evaporation ponds and irrigation drain-water wetlands, both human-created habitats, have elevated levels of selenium which cause deformed embryos (Robinson et al. 1999). Fortunately for Texas birders, these problems are most prevalent in California.
A subspecies, the Hawaiian Stilt (H. m. knudseni) is classified as Endangered by the United States Fish and Wildlife Service. Under this protection the population which had fallen to about 200 in the 1940s, had recovered to about 1400 by the 1990s (Robinson et al. 1999).
DISTRIBUTION. During the 1987-1992 field work seasons of the TBBA project, observers found 108 confirmed, 99 probable and 57 possible breeding sites, mostly in the Coastal Prairies, Coastal Sand Plain, South Texas Brush Country and High Plains regions (see the region map in Lockwood and Freeman [2004]). The Trans-Pecos and Rolling Plains regions had fewer sites. In Oklahoma atlasers found 2 confirmed and 3 probable sites in the west and near the Red River ( Howery 2004).
North American Breeding Bird Survey (BBS) data indicate the highest relative abundances of stilts (>30 per route) occur around the Salton Sea in California and the Great Salt Lake in Utah. Relative abundances of 10-30 were found in the Klamath Basin of Oregon and California and along, the Texas and Louisiana coasts (Sauer et al. 2008). Breeding also occurs in appropriate habitats in the Intermountain West, the western Great Plains, Florida, Arkansas and around the Delaware and Chesapeake bays. Northern populations migrate in winter to mingle with resident populations in the southernmost United States, Middle America, the West Indies and South America (Howell and Webb 1995, Am. Ornithol. Union 1998, Robinson et al. 1999).
SEASONAL OCCURRENCE. Rare to uncommon migrant Black-necked Stilts arrive in Texas from mid-March to mid-May with breeding occurring mid-April to mid-August, based on egg collection dates from April 16 to June 28 and downy chicks present as late as August 1. Fall migration occurs from late July to mid-October. Stilts are rare to locally uncommon on the coast in winter (Oberholser 1974, Lockwood and Freeman 2004).
BREEDING HABITAT. Black-necked Stilts nest in Texas from near sea level to about 1200 m (4000 ft). Along the coast they breed near brackish or freshwater foraging areas and at wet prairies and ponds. Inland, in areas such as the High Plains, stilts utilize fish hatcheries, sewage ponds and artificial lakes. They are not as tied to salt water as American Avocets (Oberholser 1974). In Colorado most breeding evidence was collected at wetlands with emergent vegetation and lakes with open shores on the eastern plains of the state (Winternitz 1998). In Arizona almost 80% of evidence came from marshes with emergent vegetation, sewage ponds, livestock ponds and irrigated fields (Corman 2005).
On small islands, alkali flats or dikes, either sex excavates a scrape about 13 cm (5 in) in diameter, either in the open or with vegetation around it. When materials such as grass, pebbles or shells are nearby, the nest is lined. The usual clutch size is 5 (range 1-7) smooth, tawny olive to light drab eggs; speckled and mottled to varying degrees with shades of brown. These eggs are very similar to those of American Avocets but are smaller and more heavily marked. Harrison (1979 and Robinson et al. (1999) have nest and egg photos. Incubation (by both sexes) starts after the laying of the next to last egg and lasts about 26 (range 24-29) days (Harrison 1979, Robinson et al. 1999).
The precocial young leave the nest within a day after the last chick hatches and move to an area where they will stay until they are grown. Chicks are never fed by their parents and are only brooded occasionally after their first week of life. Young birds are capable of sustained flights at 27-31 days. One brood is normally raised per year (Robinson et al. 1999).
STATUS. Black-necked Stilts are common summer residents on the Coastal Prairies and locally common inland (Lockwood and Freeman 2004). The TBBA map and that in Oberholser (1974) show similar breeding distributions along the coast, but the TBBA map shows many more breeding sites in the High Plains and along the Red River. This increase in breeding sites is consistent with data from the BBS which suggests a +7.3% annual population increase for the period 1980-2007, notably larger than the statistically significant survey-wide trend of +2.3% (Sauer et al. 2008). These data are encouraging for the future of Black-necked Stilts as a breeding species in Texas.
Text by Robert C. Tweit (2008)
Literature cited.
American Ornithologists’ Union. 1998. Checklist of North American birds, 7th ed. Am, Ornithol. Union, Washington, DC.
Corman, T. E. 2005. Black-necked Stilt (Himantopus mexicanus). In Arizona breeding bird atlas. pp. 176-177 (T. E. Corman and C. Wise-Gervais, eds.), University of New Mexico Press, Albuquerque.
Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston, MA.
Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, New York.
Howery, M. 2004. Black-necked Stilt (Himantopus mexicanus). In Oklahoma breeding bird atlas, pp. 144-145 (D. L. Reinking, ed.). University of Oklahoma Press, Norman.
Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station.
Oberholser, H. C. 1974. The bird life of Texas. University of Texas Press, Austin.
Robinson, J. A., J. M. Reed, J. P. Skorupa and L. W. Oring. 1999. Black-necked Stilt (Himantopus mexicanus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from: http://bna.birds.cornell.edu/bna/species/449
Sauer, J. R., J. E. Hines, and J. Fallon. 2008. The North American breeding bird survey, results and analysis 1966-2007. Version 5.15.2008. USGS Patuxent Wildlife Research Center, Laurel MD < http://www.mbr-pwrc.usgs.gov/bbs>
Winternitz, B. L. 1998. Black-necked Stilt (Himantopus mexicanus). In Colorado breeding bird atlas, pp. 172-173 (H. E. Kingery, ed.), Colorado Bird Atlas Partnership, Denver.