Stilts and Avocets
Stilts and Avocets
Stilts and avocets are long–legged, long–beaked wading birds of the muddy shores of shallow lakes and lagoons, including both fresh and saline waters. There are fewer than 10 species of stilts and avocets, all of which are included in the family Recurvirostridae. These birds occur in the temperate and tropical zones of all of the continents except Antarctica. The bill of stilts is rather straight, while that of avocets curves upwards, and that of the ibisbill curves downwards.
The habitat of the ibisbill (Ibidorhyncha struthersii) is the shores of cold, glacial streams of the mountains of the Himalayas. The Andean avocet (Recurvirostra andina) utilizes similarly cold, but shallow–lake habitat in the Andes of South America.
Stilts and avocets feed on small invertebrates on the water surface or at the mud–water interface. The ibisbill feeds by probing among the cobble and pebbles of the cold streams that it inhabits.
Stilts and avocets commonly construct nests as mounds of vegetation, on the boggy edges of lakes or on islands. The chicks of these species are precocial, meaning that they can leave the nest within a short time of being born. Remarkably, stilt and avocet chicks feed themselves, and are not fed by their parents.
Some stilts and avocets breed in semi–arid climates, where the rainfall is unpredictable. Under such conditions, these birds nest opportunistically, whenever recent rains have been sufficient to develop wetlands containing enough water to support the breeding effort of these birds. Stilts and avocets tend to be gregarious, forming small breeding colonies numbering as many as tens of pairs. After breeding has been accomplished, birds from various colonies congregate in flocks that can number hundreds of birds.
Species of stilts and avocets
The American avocet (Recurvirostra americana) is a chestnut–headed bird with a white body and black wings. This species is relatively abundant, and breeds on the shores of shallow lakes and marshes in the western United States and adjacent parts of Canada. The black–necked stilt (Himantopus mexicanus) is more southwestern in its distribution in the United States. Both of these species are migratory, mostly spending the winter months in Central America.
The Hawaiian stilt or ae’o (Himantopus mexicanus knudseni) is a distinct subspecies of the black–necked
stilt that breeds in wetlands in the Hawaiian Islands. Fewer than 1,000 pairs of this bird remain. The sub–species is considered to be endangered, mostly by the loss of its wetland habitat through conversion to agricultural uses or for residential or tourism development.
The pied or black–winged stilt (Himantopus himantopus) is a very wide–ranging species, occurring in suitable habitat in Eurasia, Africa, Southeast Asia, and Australia. The black–winged stilt (Himantopus melanurus) of South America is closely related to the previous species. The banded stilt (Cladorhynchus leucocephalus) occurs in Australia.
The pied avocet (Recurvirostra avosetta) occurs in parts of Eurasia and Africa. Australia has a rednecked avocet (R. novaehollandiae), while the Andean avocet (R. andina) occurs in montane habitats of South America.
The ibisbill (Ibidorhyncha struthersii) occurs in the mountain zone of the Himalayan Mountains of south Asia.
Most ornithologists believe that the family Recurvirostridae is not a very natural grouping of birds. The several species of avocets are obviously closely related to each other, as are the various stilts.
However, the ibisbill does not seem to be closely related to the stilts and avocets, and may eventually be assigned to a separate family.
See also Endangered species; Migration.
Resources
BOOKS
del Hoyo, J., A. Elliott, and J. Sargatal. Handbook of the Birds of the World. Vol. 3,Hoatzin to Auks. Barcelona: Lynx Edicions, 1996.
Forshaw, Joseph. Encyclopedia of Birds. 2nd ed. New York: Academic Press, 1998.
PERIODICALS
Robinson, Julie A., et al. “American Avocet.” The Birds of North America 275 (1997).
Bill Freedman