STILTS AND AVOCETS FACTS
Stilts and avocets range from 14 to 20 inches (35 to 51 centimeters) in height and from 5.8 to 16.2 ounces (166 to 461 grams) in weight. All species have striking bill shapes. In avocets, the bills curve upward, particularly in females. The ibisbill has a bill that curves downward. In stilts, the bills are generally straight or slightly curved. Stilts and avocets have the longest legs (in proportion to body size) of any shorebirds. These may be red, blue, or gray in color. Most stilts and avocets are black and white in color, sometimes with reddish-brown areas.
Stilts and avocets are found worldwide, on all continents except Antarctica. The largest number of species occupy areas near Australia.
STILTS AND AVOCETS HABITAT
Most stilts and avocets occupy large wetland areas. The ibisbill, however, prefers rocky habitats along slow-moving streams. Avocets, as well as the banded stilt, generally live in saltwater wetlands. Other stilt species use both saltwater and freshwater wetlands. The Andean stilt occurs only close to high altitude saline lakes. Many stilt and avocet species also use man-made areas as habitat, including dams, irrigation sites, and sewer ponds.
STILTS AND AVOCETS DIET
Stilts and avocets eat aquatic invertebrates such as crustaceans, insect larvae, worms, and mollusks. They also eat small fish and, sometimes, plant material. Stilts and avocets generally obtain food by pecking at items. In addition, some avocets swing their bills through water or soft mud and filter out small food items. Some stilts and avocets also stick their entire heads underwater to look for food. The ibisbill uses its bill to rake through pebbles in the rocky stream habitats it prefers. It then snatches whatever small aquatic animals it disturbs. Finally, some stilts and avocets have been known to snap at flying insects.
BEHAVIOR AND REPRODUCTION
A few species of stilts and avocets, such as black-winged stilts, pied avocets, and American avocets, migrate from breeding grounds to wintering grounds over the course of the year. Ibisbills migrate altitudinally, moving from higher to lower elevations and back. In addition, most species move short distances to find suitable wetland areas.
Most species of stilts and avocets form large flocks while feeding. Flocks can include several thousand individuals. In most cases, feeding occurs during the daytime. However, some stilts also feed at night. Stilts and avocets generally roost, or spend the night, standing in water. They may also rest during the day, either sitting on the ground or standing on one foot with the head tucked under the wing. Unlike other members of the group, ibisbills are usually found alone, in pairs, or in much smaller groups that rarely exceed seven or eight individuals.
Except for the ibisbill, stilt and avocet species also nest in large colonies, groups, which may include multiple shorebird species. Breeding colonies tend to be very noisy. Stilts and avocets use a variety of calls to communicate with mates or offspring, or to signal danger.
Most stilts and avocets are monogamous (muh-NAH-guhmus), with a single male breeding with a single female at one time. Birds may change mates over the course of a breeding season, however. To attract females, males perform a display that involves dipping their heads, shaking, and then preening, or smoothing their feathers. After mating, the male and female cross bills and walk together, the male holding one wing over the back of the female. Generally, the female lays three or four eggs at a time. Both the male and the female participate in incubating, or sitting on the eggs, and feeding and protecting the chicks once they hatch. Adults dive-bomb potential predators and may also fake a broken wing in order to distract intruders and draw them away from the nest.
STILTS, AVOCETS, AND PEOPLE
There are no significant interactions between most species of stilts and avocets and people. However, humans have appreciated these birds for a long time and are generally enthusiastic about conservation measures to help protect populations.
The black stilt, which is restricted to New Zealand, is considered Critically Endangered, facing an extremely high risk of extinction. It has suffered primarily from habitat destruction and non-native predators introduced by humans, which eat large numbers of black stilt eggs. There are currently fewer than 100 black stilts in existence. The Hawaiian subspecies of the black-winged stilt is also considered Endangered, facing a very high risk of extinction. There are approximately 1,800 individuals left in the wild. Populations have declined due to habitat destruction and predators introduced by humans.