Birds of Keālia Pond
Hawaiian Stilt / Himantopus mexicanus knudseni / Ae‘o (one standing tall)
The population of ae‘o is estimated at 1200-1500 individuals throughout the islands. The species was listed as endangered in 1970 as wetlands were being altered. More than half the population (maximum 1074 birds) has been recorded at Keālia Pond when water level is shallow. Although ae‘o can be observed in ephemeral pockets of water throughout the islands, their habitat for foraging and successfully nesting is limited to protected areas where predators (mongooses, feral cats, rats, and feral dogs) are controlled.
Ae‘o prefer shallow water no more than seven inches in depth. Nesting sites are on exposed mudflats and low islands with adjacent water (fresh, brackish, or salt water) and vegetation. Nests are either made from a pile of sticks or just a shallow nest depression on the ground.
Feeding habitats are shallow bodies of water providing them with a wide variety of aquatic invertebrates and small fish. Ae‘o use picking and bill sweeping to obtain prey items in the soil and water column.
The onset of ae‘o breeding season is when water level in the ponds recede and mudflats are exposed, usually in late March-early April at Keālia Pond NWR. Nests consist of vegetation material with a depression in the middle or just a depression in the soil. Four brown speckled eggs are laid and incubated approximately 24 days. Ae‘o chicks are precocious – once hatched they are mobile and feeding on their own, but under the watchful eyes of their parents. Chicks resemble their eggs with brown and off-white speckles until they obtain feathers similar to the adults. Breeding season, including chick fledging, is completed by mid August.
Movement of ae‘o between wetlands on Maui and other islands are known from sightings of color-banded birds. Ae‘o are vocal even during the nonbreeding season. They actively defend their nests and chicks with calls and dive-bombing to detract the predator or disturbances. Upon threat of predators or humans, adults vocalize to warn chicks who in turn will crouch down and remain motionless, using their camouflaged down to blend with the ground.
The ae‘o are the most vulnerable to nonnative mammalian and avian predators (cattle egrets) and are easily disturbed by human activities. During breeding season at Keālia Pond (April to July) areas of the Kanuimanu Ponds may be inaccessible to the public to allow birds to successfully incubate and raise their chicks.