The
Black-necked Stilt (
Himantopus mexicanus) is a locally abundant shorebird of
AmericanThe Americas, or America, are lands in the Western hemisphere or New World, comprising the continents of North America and South America with their associated islands and regions. America may be ambiguous in English, as it is more commonly used to refer to the United States of America...
wetlands and coastlines. It is found from the coastal areas of
CaliforniaCalifornia is the most populous state in the United States, and the third largest by area. California is the second most populous sub-national entity in the Americas, behind only São Paulo, Brazil...
through much of the interior western United States and along the
Gulf of MexicoThe Gulf of Mexico is the ninth largest body of water in the world. Considered a smaller part of the Atlantic Ocean, it is an ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United...
as far east as
FloridaFlorida is a state located in the southeastern region of the United States, bordering Alabama to the northwest and Georgia to the north. It was the 27th state admitted to the United States...
, then south through
Central AmericaManagua
Guatemala City
San Salvador
San Pedro Sula
Panama City
San José, Costa Rica
Santa Ana, El Salvador
León
San Miguel|-|}...
and the
CaribbeanThe Caribbean is a region consisting of the Caribbean Sea, its islands , and the surrounding coasts...
to NW
BrazilBrazil , officially the Federative Republic of Brazil , is a country in South America. It is the fifth largest country by geographical area, occupying nearly half of South America, the fifth most populous country, and the fourth most populous democracy in the world. Bounded by the Atlantic Ocean...
SW
PeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean.Peruvian territory was home to the Norte Chico...
, E
EcuadorEcuador , officially the Republic of Ecuador , literally, "Republic of the equator") is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America that...
and the
Galápagos IslandsThe Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, 972 km west of continental Ecuador...
. The northernmost populations, particularly those from inland, are
migratoryBird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. These however are usually irregular or in only one direction and are termed variously as nomadism, invasions,...
, wintering from the extreme south of the USA to southern
MexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, rarely as far south as
Costa RicaCosta Rica, officially the Republic of Costa Rica is a country in Central America, bordered by Nicaragua to the north, Panama to the east and south, the Pacific Ocean to the west and south and the Caribbean Sea to the east.Costa Rica, which translates literally as "Rich Coast", constitutionally...
; on the
Baja CaliforniaBaja California is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North Territory of Baja California. It has an area of , or 3.57% of the land mass of Mexico and comprises the northern half of the Baja California peninsula, north...
peninsula it is only found regularly in winter.
Taxonomy
It is often treated as a
subspeciesSubspecies in biological classification, is 1) a taxonomic rank subordinate to species, or 2) a taxonomic unit, a taxon in that rank...
of the Common or
Black-winged StiltThe Black-winged Stilt is a widely distributed very long-legged wader in the avocet and stilt family . Opinions differ as to whether the birds treated under the scientific name H. himantopus ought to be treated as a single species and if not, how many species to recognize...
, using the trinomial name
Himantopus himantopus mexicanus. However, the
AOUThe American Ornithologists' Union is an ornithological organization in the USA. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birders...
has always considered it a
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
in its own right, and the scientific name
Himantopus mexicanus is often seen. Matters are more complicated though; sometimes all five distinct lineages of the Common Stilt are treated as different species. But the White-necked Stilt from southern
South AmericaSouth America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...
(
H. h. melanurus when only one species is recognized), parapatric and intergrading to some extent with its northern relative where their ranges meet, would warrant inclusion with the Black-necked stilt when this is separated specifically, becoming
Himantopus mexicanus melanurus. Similarly, the Hawaiian Stilt,
H. h. knudseni, is likely to belong to the American species when this is considered separate; while some treat it as another distinct species, the AOU,
BirdLife InternationalBirdLife International is the international conservation organization working to protect the world’s birds and their habitats...
and the IUCN do not. Thus, in their scheme the Black-necked Stilt is properly named
Himantopus mexicanus mexicanus.
Description
Adults have long pink legs and a long thin black bill. They are white below and have black wings and backs. The tail is white with some grey banding. A continuous area of black extends from the back along the hindneck to the head. There, it forms a cap covering the entire head from the top to just below eye-level, with the exception of the areas surrounding the bill and a small white spot above the eye. Males have a greenish gloss to the back and wings, particularly in the breeding season. This is less pronounced or absent in females, which have a brown tinge to these areas instead. Otherwise, the sexes look alike.
Downy young are light olive brown with lengthwise rows of black speckles (larger on the back) on the upperparts – essentially where adults are black – and dull white elsewhere, with some dark barring on the flanks.
Where their ranges meet in centrral
BrazilBrazil , officially the Federative Republic of Brazil , is a country in South America. It is the fifth largest country by geographical area, occupying nearly half of South America, the fifth most populous country, and the fourth most populous democracy in the world. Bounded by the Atlantic Ocean...
, the Black-necked and White-backed stilts intergrade. Such individuals often have some white or grey on top of the head and a white or grey collar separating the black of the hindneck from that of the upper back.
The Black-necked Stilt is distinguished from non-breeding vagrants of the
Old WorldThe Old World consists of those parts of Earth known to Europeans, Asians, and Africans in the 15th century.-Regions:The Old World includes Europe, Asia, and Africa , plus surrounding islands...
Black-winged Stilt by the white spot above the eye. Vagrants of the northern American form in turn is hard to tell apart from the resident Hawaiian Stilt, in which only the eye-spot is markedly smaller. But though many stilt populations are long-distance migrants and during their movements can be found hundreds of miles offshore, actual trans-oceanic vagrants are nonetheless a rare occurrence.
Distribution and habitat
The Black-necked Stilt is found in estuarine,
lacustrineLacustrine means "of a lake" or "relating to a lake".Specifically, it may refer to:*Lacustrine plain*Lacustrine delta-See also:*Limnic, of or relating to freshwater*Palustrine, of or relating to a marsh*Riverine, of or relating to a river...
, salt pond and emergent
wetlandA wetland is an area of land whose soil is saturated with moisture either permanently or seasonally. Such areas may also be covered partially or completely by shallow pools of water. Wetlands include swamps, marshes, and bogs, among others. The water found in wetlands can be saltwater, freshwater,...
habitatThe term habitat has a number of meanings:* Habitat , a place where a species lives and grows** Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s; it is generally a lowland bird but in
Central AmericaManagua
Guatemala City
San Salvador
San Pedro Sula
Panama City
San José, Costa Rica
Santa Ana, El Salvador
León
San Miguel|-|}...
has been found up to 8,200 ft (2,500 m)
ASLThe term above mean sea level refers to the elevation or altitude of any object, relative to the average sea level datum. AMSL is used extensively in radio by engineers to determine the coverage area a station will be able to reach...
and commonly seen in
llanosLos llanos is a vast tropical grassland plain situated at the east of the Andes in northwestern South America . Its main river is the Orinoco, which forms part of the border between Colombia and Venezuela and is the major river system of Venezuela.The climate change of the Llanos is extreme...
habitat in northern
South AmericaSouth America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...
. It is also found in seasonally flooded wetlands. Use of
salt evaporation pondSalt evaporation ponds are shallow man-made ponds designed to produce salts from sea water or other brines. The seawater or brine is fed into large ponds and water is drawn out through natural evaporation which allows the salt to be subsequently harvested. The ponds also provide a productive...
s has increased significantly since 1960 in the USA, and they may now be the primary wintering habitat; these salt ponds are especially prevalent in southern
San Francisco BaySan Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
. At the
Salton SeaThe Salton Sea is a saline, endorheic rift lake located directly on the San Andreas Fault. The lake occupies the lowest elevations of the Salton Sink in the Colorado Desert of Riverside and Imperial Counties in Southern California. Like Death Valley, it is located below sea level, with the current...
, the Black-necked Stilt is resident year-round.
This bird is locally abundant in the
San Joaquin ValleyThe San Joaquin Valley refers to the area of the Central Valley of California that lies south of the Sacramento-San Joaquin Delta in Stockton...
, where it commonly winters. It is common to locally abundant in appropriate habitat in southern
CaliforniaCalifornia is the most populous state in the United States, and the third largest by area. California is the second most populous sub-national entity in the Americas, behind only São Paulo, Brazil...
from April to September.
It also breeds along lake shores in northeastern California and southeastern
OregonOregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
as well as along the
Colorado RiverThe Colorado River , or the Red River, is a river in the southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains...
. In North America outside California, the Black-necked Stilt rarely breeds inland, but it is known as a breeding bird in riparian locales in
ArizonaThe State of Arizona is a state located in the southwestern region of the United States. The capital and largest city is Phoenix. The second largest city is Tucson, followed in size by the four Phoenix metropolitan area cities of Mesa, Glendale, Chandler, and Scottsdale.Arizona was the 48th and...
and elsewhere in the southern USA. In Arizona, Black-necked Stilts may been seen along artificially-created lakes and drainage basins in the
PhoenixPhoenix is the capital and largest city of the U.S. state of Arizona, as well as the fifth most populous city in the United States...
metropolitan area, in remnant riparian habitat.
In the
San Francisco Bay AreaThe San Francisco Bay Area, commonly known as the Bay Area, or the Yay Area, is a metropolitan region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses large cities such as San Francisco, Oakland, and San Jose, along with smaller urban and...
, specific locations where one would expect to see this bird are
Richardson BayRichardson Bay is a shallow, ecologically rich arm of San Francisco Bay, managed under a Joint Powers Agency of four Northern California cities. The Richardson Bay Sanctuary was acquired in the early 1960s by the National Audubon Society. The bay was named for William A...
(especially, according to mudflat bird sightings, the mouth of Pickleweed Creek), mudflats of Belmont Slough, mudflats of
Seal SloughSeal Slough is a narrow winding tidal channel through a tidal marsh in San Mateo and Foster City, California. This slough has been the object of a wetland restoration project in recent years to enhance habitat value. Dredging has been carried out in Seal Slough since at least 1954...
in
San MateoSan Mateo is a city in San Mateo County, California, United States, in the San Francisco Bay Area. It is one of the larger suburbs on the San Francisco Peninsula, located between Burlingame to the north, Foster City to the east, and Belmont to the south...
, salt ponds in
HaywardHayward is a city located in the East Bay in Alameda County. The sixth largest city in the San Francisco Bay Area, it is one of the larger suburbs of Oakland. As of the 2000 census, the city population was 140,030. The estimated population in 2007 is 155,312. The former suburbs of Mt...
,
CaliforniaCalifornia is the most populous state in the United States, and the third largest by area. California is the second most populous sub-national entity in the Americas, behind only São Paulo, Brazil...
, exposed
bay mudBay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacial cycles...
s on the
BurlingameBurlingame is a city in San Mateo County, California. It is located on the San Francisco Peninsula and has a significant shoreline on San Francisco Bay. The city is named after diplomat Anson Burlingame. It is renowned for many surviving examples of Victorian architecture and its high residential...
estuarineAn estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries are thus subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of...
shore, and Heron's Head Park at
India BasinIndia Basin is the easternmost neighborhood of San Francisco, California.The parameters of India Basin are roughly the neighborhood surrounding Cargo Way, Third Street, Evans and Innes Avenues to the Hunters Point Naval Shipyard, from the top of the hill to the water.The history of India Basin is a...
.
For the populations that summer in the Sierra Nevada of northeast California and southeastern Oregon as well as the plateau lakes of those areas, breeding occurs after those flocks
migrateBird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. These however are usually irregular or in only one direction and are termed variously as nomadism, invasions,...
to lowland and coastal areas each August or September. For flocks that summer in the northern Central Valley of California, a migration occurs to the
San Joaquin ValleyThe San Joaquin Valley refers to the area of the Central Valley of California that lies south of the Sacramento-San Joaquin Delta in Stockton...
to consolidate with flocks that were already summering there. In coastal areas flocks both summer and winter in these estuarine settings.
Fall migration of the northernly birds takes place from July to September, and they return to the breeding grounds between March and May Usually, the entire population breeding at any one site arrives and leaves again within one month or less, migrating in flocks of about 15 individuals. There is some seasonal movement of the tropical populations, but this is not long-range and poorly understood.
The parasitic
cyclocoelineThe Cyclocoelinae are a subfamily of parasitic flatworms of the order Echinostomida. Their definite hosts are waterfowl and other birds such as waders, where the worms are mainly found in the airways.-Genera:...
flatwormThe flatworms, known in scientific literature as Platyhelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
Neoallopyge americanensis was described from the air sacs of a Black-necked Stilt from
TexasTexas is the second-largest U.S. state in both area and population, and the largest state in the contiguous United States.The name had wide usage among native Americans, meaning "friends" or "allies"...
. Its
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
is presently
monotypicIn biology, a monotypic taxon is a taxonomic group with only one type. The usage differs slightly between botany and zoology:In botany, a monotypic taxon is a taxon that has only one species: Ginkgo is a monotypic genus, while Ginkgoaceae is a monotypic family...
and seems to be closely related to the similar genus
Allopyge, found in
Old WorldThe Old World consists of those parts of Earth known to Europeans, Asians, and Africans in the 15th century.-Regions:The Old World includes Europe, Asia, and Africa , plus surrounding islands...
craneCranes are large, long-legged and long-necked birds of the order Gruiformes, and family Gruidae. There are fifteen species. Unlike the similar-looking but unrelated herons, cranes fly with necks outstretched, not pulled back...
s.
Food and feeding
The Black-necked Stilt forages by probing and gleaning primarily in mudflats and lakeshores, but also in very shallow waters near shores; it seeks out a range of aquatic invertebrates – mainly
crustaceanCrustaceans are a very large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles...
s and other
arthropodAn arthropod is an invertebrate that has an exoskeleton , a segmented body, and jointed attachments called appendages. Arthropods are animals belonging to the Phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s, and mollusks – and small
fishA fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins...
,
tadpoleA tadpole, polliwog , or pollywiggle is the wholly aquatic larval stage in the life cycle of an amphibian, particularly of a frog or toad.- Appellation :The name "tadpole" is from Middle English taddepol, made up of the elements tadde, "toad", and...
s and very rarely plant seeds. Its mainstay food varies according to availability; inland birds usually feed mainly on aquatic
insectInsects are arthropods, having a hard exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae. They are the most diverse group of animals on the planet and include more than a million species that are already described. Insects represent more than half of all...
s and their
larvaA larva is a young form of animal with indirect development, going through or undergoing metamorphosis ....
e, while coastal populations mostly eat other aquatic invertebrates. For feeding areas they prefer coastal estuaries, salt ponds, lakeshores, alkali flats and even flooded fields. For roosting and resting needs, this bird selects alkali flats (even flooded ones), lake shores, and islands surrounded by shallow water.
Breeding
This stilt chooses mudflats, desiccated
lacustrineLacustrine means "of a lake" or "relating to a lake".Specifically, it may refer to:*Lacustrine plain*Lacustrine delta-See also:*Limnic, of or relating to freshwater*Palustrine, of or relating to a marsh*Riverine, of or relating to a river...
verges, and
leveeA levee, levée, dike , embankment, floodbank or stopbank is a natural or artificial slope or wall to regulate water levels...
s for nest locations, as long as the soil is friable. Reproduction occurs from late April through August in
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, with peak activity in June, while tropical populations usually breed after the rainy season. The nests are typically sited within one kilometer of a feeding location, and the pairs defend an extensive perimeter around groups of nests, patrolling in cooperation with their neighbors. Spacing between nests is approximately 65 ft (c.20 m), but sometimes nests are within 7 ft (2 m) of each other and some nests in the
rookeryA rookery is a colony of breeding animals. The term Rookery has also been used as a name for dense slum housing in nineteenth-century cities, and especially London....
are as far as 130 ft (40 m) from the nearest neighbor. The Black-necked Stilt is actually classified as
semicolonialColonization, , occurs whenever any one or more species populate an area. The term, which is derived from the Latin colere, "to inhabit, cultivate, frequent, practice, tend, guard, respect," originally related to humans...
since the nests are rarely found alone and colonies usually number dozens, rarely hundreds of pairs. The nests are frequently established rather close to the water edge, so that their integrity is affected by rising water levels of ponds or tides. This is particularly a hazard in the case of managed salt ponds where water levels may be altered rapidly in the salt pond
floodA flood is an overflow or accumulation of an expanse of water that submerges land. In the sense of "flowing water", the word may also be applied to the inflow of the tide....
ing process.
The
clutchA clutch of eggs refers to all the eggs produced by birds or reptiles often at a single time, particularly those laid in a nest.-Size:Clutch size will differ greatly between species, sometimes even within the same genus. It may also differ within the same species due to many factors including...
size generally is 3-5 eggs with an average of four. For 22–26 days both sexes take turns
incubatingIncubation is the process by which birds hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of sitting on eggs to incubate...
the eggs. The young are so
precocialIn Biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born helpless. Extremely precocial species may be called "superprecocial."...
that they are seen swimming within two hours after hatching and are also capable of rapid land
velocityIn physics, velocity is the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. In the SI system, it is measured in meters per second: or ms-1. The scalar absolute value of velocity is speed...
at that early time. In spite of this early development the young normally return to the nest for resting for one or two more days. They fledge after about one month but remain dependent on their parents for some more weeks. Birds begin to breed at 1–2 years of age.
Status
Particularly the North American populations of the Black-necked Stilt have somewhat declined in the 20th century, mainly due to conversion of habitat for human use and
pollutionPollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms . Pollution can take the form of chemical substances, or energy, such as noise, heat, or light...
affecting both the birds directly as well as their food stocks. But altogether, the population is healthy and occurs over a large range. This stilt is therefore classified as a Species of
Least ConcernLeast Concern is an IUCN category assigned to extant species or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, nor Near Threatened, nor Conservation Dependent...
by the IUCN. The Hawaiian Stilt, separated with the Black-necked Stilt in a distinct species by some (including the IUCN), is very rare however and numbers less than 2,000 individuals.
PredationIn ecology, predation describes a biological interaction where a predator feeds on its prey, . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of the prey...
by the Small Indian Mongoose (
Herpestes javanicus auropunctatus), introduced to hunt rats, is suspected to have contributed to its decline.
Further reading
(1986):
Shorebirds: an identification guide to the waders of the world. Houghton Mifflin, Boston.
ISBN 0-395-60237-8 (1989):
A guide to the birds of Costa Rica. Comistock, Ithaca.
ISBN 0-8014-9600-4
External links