Black-Necked Stilt

Five species of similar-looking stilts are recognized in the genus Himantopus. They have the second-longest legs in proportion to their bodies of any bird, exceeded only by flamingos. The Black-necked stilt is a study in contrasts. The male’s shiny black wings and back set off the white breast, and both are accentuated by the long, rose-pink legs. That black coloration on top extends from the back along the neck to the head, forming a cap which covers the entire head from the top to just below eye-level. The female’s coloration is similar, but a bit more brown than glossy black on top. Both have white rings around the eyes, red irises, a long neck, and a long, thin black bill that curves upwards ever so slightly. Stilts belong to the family Recurvirostridae which, in Latin, means "bent bill." Juveniles look similar to adults but they have a faint scalloped pattern on their backs and paler legs. Black-necked stilts have partially webbed feet, which allow them to swim, though they rarely do. They reach a height of 13 to 17 inches, with about a 27-inch wingspan. Fun fact: ever wonder why bird “knees” bend backwards? That’s because it’s not a knee; it’s a heel. A bird’s true knee joint is closer to the body, where the femur (thigh) meets the tibia and fibula (basically the drumstick). The long, lower portion of a stilt’s leg is called the tarsometatarsus, and it’s essentially a stretched-out, fused version of what in humans are the ankle and foot bones.

Black-necked stilts are almost always seen near shallow water, including both salt and fresh water, such as mudflats, salt pans, saltmarshes, flooded areas along rivers, shallow lagoons, mangrove swamps, and many human-modified habitats such as sewage ponds, evaporation pools, rice fields, and flooded fields. In some areas, stilts actually favor these habitats over available natural habitats. Generally a lowland bird, but in Central America, it has been found up to 8,200 feet above sea level. This common shorebird ranges from the coastal areas of California through much of the interior western United States and along the Gulf of Mexico as far east as Florida, then south through Central America to Argentina, the Caribbean to Ecuador, and the Galápagos Islands. The northernmost populations, particularly those from inland, are migratory; they winter in southern Mexico, Brazil, Peru, the West Indies, and southern parts of the Pacific and Atlantic coasts.

When they are not resting or preening, black-necked stilts spend much of the day hunting in shallow waters in search of food. Though they can swim and dive if necessary, they prefer to wade as they feed, probing with their long, thin bill for prey that is on or near the surface of water. They find most of their food visually, capturing insects, small crustaceans, and tiny fish with a quick peck. They also swing the bill side to side in the water to skim invertebrates from the surface or just below. To capture small fish, they sometimes chase them into the shallows, where the fish become trapped. They are opportunistic and prey on many creatures, including larval mosquitoes, soldier flies, brine flies, caddisflies, dragonflies, mayflies, crickets, grasshoppers, many kinds of beetles (including weevils), mollusks, water-boatmen, crayfish, shrimp, tadpoles, and very small frogs and fish. Floating seeds and vegetation form a tiny part of their diet. They move deliberately when foraging, walking slowly through wetlands in search of tiny aquatic prey, seldom swimming. For feeding areas, they prefer coastal estuaries, salt ponds, lakeshores, alkali flats, flooded fields, etc. For roosting and resting, this bird selects alkali flats (even flooded ones), lake shores, and islands surrounded by shallow water to deter at least some of their main predators – such as foxes, skunks, and coyotes – though it doesn’t help much with others like gulls and birds of prey.

Left to their own devices, stilts wade through shallow wetlands with a careful grace. But when disturbed, especially during breeding season, all semblance of grace disappears. Adult stilts are highly territorial during breeding season, and their incessant, yapping calls carry for some distance. Males often challenge one another early in the nesting season which can result in intense conflicts involving aerial combat in which males strike each other with bills and legs. They’ll even drive out young birds and attack chicks that are not their own. When not breeding, black-necked stilts are still fairly territorial but often will put up with each other enough to roost and forage in close proximity, if never in tight flocks. Most calls are sharp and high-pitched yaps – “keek,” “kek,” or similar – often given in series when alarmed. Most people hear it when they have approached too close to a nest or young hidden in the vegetation. Quieter versions of the call, heard between adults and young, serve as contact calls.

Breeding season occurs from late April through August in North America, with peak activity in June. Black-necked stilts are especially exuberant during the breeding season, both in territoriality and courtship. To seal the bond with her chosen mate, the female stretches out her neck and preens; the male mimics her. Then, both dip their bills in the water and preen, and this action becomes increasingly flurried, with much splashing just prior to copulation. Afterward, the pair crosses their bills and dance a few steps. Both female and male choose the nest site. They look for places with soft sand or other substrate that can be scraped away to form a depression, usually on open ground or in short vegetation, surrounded by water, such as on small islands, clumps of vegetation, or even occasionally, floating mats of algae. Both also contribute to nest construction. A completed nest may be a simple scrape in the soil or a mound of vegetation built up above water level and lined with pebbles, shells, and debris. Most lining is added to the nest during incubation and consists of whatever material is closest.

The black-necked stilt is classified as semicolonial: defending individual territories and mates, but joining with other nesting birds to drive out threats. They typically nest in loose colonies, sometimes mixed with avocets, least terns, and Wilson’s plovers. Spacing between nests ranges, but averages about 65 feet apart. Pairs defend an extensive perimeter around groups of nests, patrolling in cooperation with their neighbors. Agitated stilts yap incessantly, dive at predators, feign broken wings, and pretend to incubate in non-nest areas in order to lure predators away. A unique distraction the stilt uses is the ‘popcorn display.’ All the adult stilts in a colony alternately hop up and down while wildly flapping their wings and calling loudly at offending intruders. Sometimes, stilts will strike humans from behind with their legs if the humans approach the nest too closely. Despite a certain degree of cooperative defensive behavior, black-necked stilts are still territorial to each other, driving away others of their kind to maintain distance between their nests, and were it not for their joining in these antipredator displays, stilts would probably be considered territorial rather than semicolonial.

Clutch size is 2-5 brown-speckled eggs, which hatch in 24-29 days. There is only one successful brood a year. Both parents incubate the eggs. On very hot days, stilts may soak their belly feathers to carry water to the nests, sometimes making more than a hundred trips a day to keep their eggs cool. As with most other ground-nesting birds, the young are precocial (relatively well-developed), and downy chicks leave the nest only an hour or two after hatching and are able to run and swim as soon as their down is dry. And although both parents tend the chicks, they are capable of feeding themselves. They fly in 4-5 weeks. Downy young are light olive brown with lengthwise rows of black speckles on the back – essentially where adults are black – and dull white elsewhere, with some dark barring on the flanks. Both parents participate in chick-rearing, though males appear to accompany older chicks more often than females. The pair bond is maintained through nesting and chick rearing, but if a nest fails, stilts sometimes begin again with a different mate.

Black-necked stilts and American avocets belong to the same family (Recurvirostridae), and they are capable of hybridizing and producing young, though these hybrid offspring are rare. Birders who have documented this cross have given them the nickname “avo-stilts.” Stilts reach sexual maturity around one year. The oldest recorded black-necked stilt was at least 12 years, 5 months old. it was banded in Venezuela and recaptured in the Lesser Antilles.

In the nineteenth century, stilts were hunted throughout their range, but populations have been stable between 1966 and 2015 in continental North America, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 900,000 birds, with a Continental Concern Score of 8 out of 20, indicating it is a species of low conservation concern. There is some evidence of range expansion to the north, possibly attributable to climate change. Although stilt populations in the continental U.S. appear stable, a Hawaiian subspecies, the Ae'o, is considered federally endangered and is particularly threatened by introduced predators, including feral cats.

Because stilts are wetland birds, they are vulnerable to wetland destruction, degradation, and especially pollution – including pesticides, heavy metals, and other elements such as selenium. Stilts are sometimes monitored as indicators of contaminated irrigation water in the environment at large. Both stilts and avocets congregate on human-made evaporation ponds to catch the abundant brine flies. While use of evaporation ponds might seem to ensure that suitable habitat will be available for stilts in the future, these ponds also accumulate contaminants. Embryo deformities associated with selenium contamination in irrigation drain water were first identified at Kesterson National Wildlife Refuge and later at the many evaporation ponds of the Tulare Basin, CA. The harmful effects of selenium on hatching success have been documented, and the effects on chick growth and survivorship are under study. Additionally, since their nests are frequently rather close to the water edge, they are affected by rising water levels of ponds or tides. This is particularly a hazard in the case of these managed salt ponds where water levels may be altered rapidly in the salt pond flooding process. The cumulative effects of wetland contamination and shifts in habitat availability on stilt populations remain to be seen.

Where I learned about black-necked stilts, and you can too!

Audubon
www.audubon.org/field-guide/bird/black-necked-stilt

The Cornell Lab: All About Birds
www.allaboutbirds.org/guide/Black-necked_Stilt/overview

The Cornell Lab of Ornithology: Birds of the World
birdsoftheworld.org/bow/species/bknsti/cur/introduction

TPWD
tpwd.texas.gov/huntwild/wild/species/stilt/

American Bird Conservancy
abcbirds.org/bird/black-necked-stilt/

Project Noah
www.projectnoah.org/spottings/1651283809

Missouri Dept of Conservation
mdc.mo.gov/discover-nature/field-guide/black-necked-stilt

eBird
ebird.org/species/bknsti

Bird Advisors
www.birdadvisors.com/black-necked-stilt/

Animalia
animalia.bio/black-necked-stilt

Wikipedia
en.wikipedia.org/wiki/Black-necked_stilt