Wetland Birds of the Hawaiian Islands
Wetland Birds of the Hawaiian Islands
Wetland Birds of the Hawaiian Islands
Hawaiian Black-Necked Stilt (Ae‘o)
Hawaiian Coot (‘Alae Ke‘oke‘o)
Hawaiian Duck (Koloa Maoli)
Hawaiian Moorhen (‘Alae ‘Ula)
Black-Crowned Night-Heron (‘Auku‘u)
Threats to Wetland Bird Species of the Hawaiian Islands
Hawaiian Black-Necked Stilt (Himantopus mexicanus knudseni)
Hawaiian Name: Ae‘o
Status: Endangered Species. Found on Hawai‘i Island, Maui, Lāna‘i, Moloka‘i, O‘ahu, Kaua‘i and Ni‘ihau.
[Illustration: Hawaiian Black-Necked Stilt]
Perfectly suited to a wetland environment, the Hawaiian Black-necked stilt is a wading bird, easily identified by its long, skinny pink legs, black and white forehead, and white breast.
Black-necked stilts grow to about 16 inches (41 cm) tall. The birds’ long, jointed legs bend in the opposite direction of the human leg.
A thin, long-legged person.
Hawaiian stilts are known as ae‘o, which means “one standing tall,” or kukuluae‘o, which is also the Hawaiian term for wooden stilts that were used for amusement by Hawaiian children in ancient times.
The wooden stilts were most commonly made from the wood of ‘ohe (Reynoldsia sandwicensis), a tree also known by the Hawaiian term ‘ohe kukuluae‘o.
Hawaiian Black-necked stilts are wading birds that often gather in groups. They make a chirping sound similar to “kip kip” or “keek, keek” and use their long beaks to probe the shallow water mud flats for food, including worms, aquatic insects, crabs, fish and mollusks.
The stilt breeding and nesting season is from December to August (predominantly from March to August). The stilt builds a nest in a shallow depression in a small mound, often on the banks of lo‘i kalo (taro patches) or in low-lying vegetation areas near the water. The stilt lines its nest with rocks and twigs.
The female stilt usually lays four eggs. The eggs are well camouflaged, and the stilt aggressively defends the nest. The eggs incubate for 24 to 26 days.
The stilt chick is covered with a downy, tannish-brown coat speckled with black, and leaves the nest soon after hatching. The chicks hide under cover until ready to fly. Parents don’t feed the chick but instead help them find suitable food sources. Sometimes the parent will fake a broken wing, feigning injury in order to draw predators away from the nest and hatchlings.
Many hatchling chicks don’t make it through their first months. At least 44 stilt chicks were hatched on Kaua‘i’s Hanalei National Wildlife Refuge in 1994, but only one was observed to have fledged.
The precise causes for this low survival rate are unknown, but all of the following may play a role: diseases, parasites, poor food supply and/or food quality, and predation by bullfrogs, cats, dogs, pigs, owls, and possibly also cattle egrets and black-crowned night-heron. Large introduced bullfrogs (Rana catesbeiana) also have been seen preying on stilt chicks.
Historically, stilt populations have also suffered due to loss of wetland habitat as well as the proliferation of invasive, non-native plant species. Many stilts have died due to a soil bacteria that has caused botulism in the stilts’ food sources. This has caused sporadic but large die-offs of affected birds.
Black-necked stilts (ae‘o) in the Hawaiian Islands constitute a subspecies of the Black-necked stilts found in North and South America, which have less black on their neck and face, and a shorter bill and tail. The North American stilts are found as far south as Brazil and also in the Galapagos Islands.
Hawaiian Black-necked stilts are known to occasionally fly between Hawaiian Islands, particularly between Ni‘ihau and Kaua‘i. The birds are found mostly in lowland areas, but are also seen at an elevation of 2,300 feet (700 m) on the island of Hawai‘i at the Pu‘u Wa‘awa‘a reservoir.
Hawaiian Black-Necked Stilt Population
Stilts were once hunted as game birds in the Hawaiian Islands. The U.S. Fish and Wildlife Service listed the Hawaiian subspecies as endangered on October 13, 1970. In 1982, the population of stilts was estimated to be less than 1,000, and found mostly on Maui and O‘ahu.
Stilts are found on O‘ahu, Hawai‘i Island, Maui, Lāna‘i, Moloka‘i, Kaua‘i and Ni‘ihau. There are currently about 1,400 to 1,800 Black-necked stilts in the Hawaiian Islands, with the biggest populations of the birds on Maui, Kaua‘i and O‘ahu. The stilt is also found on the island of Hawai‘i’s Kona Coast, where the stilt population grew to more than 220 in 2001 from an estimated 105 in 1998.
The Lāna‘i stilt population was first documented in 1989, and seems to be gradually increasing. Moloka‘i’s stilt population has also grown steadily since 1989 (an estimated 20 stilts) with at least 148 stilts on Moloka‘i in 2001.
A key factor in the growing populations appears to be the creation of new habitat suitable for the stilts. On Lāna‘i a wastewater treatment plant created the habitat, while on Moloka‘i the birds benefited from the restoration of loko i‘a (fishponds).
[Photograph: Hawaiian Black-necked stilt]
Hawaiian Coot (Fulica alai)
Hawaiian Name: ‘Alae Ke‘oke‘o or ‘Alae Kea
Status: Endangered Species. Found on Hawai‘i Island, Maui, Lāna‘i, Moloka‘i, O‘ahu, Kaua‘i.
‘Alae ke‘oke‘o, the Hawaiian coot, was formerly considered a subspecies of the American coot (Fulica americana), which is found from Panama to Canada and occasionally seen in the Hawaiian Islands.
The Hawaiian coot, now classified as a unique species (Fulica alai), is generally darker, and has a larger frontal shield and a more slender bill than its North American relatives. The Hawaiian coot also displays different patterns of white on its head than the American coot.
While the Hawaiian moorhen (‘alae ‘ula) has a red bill (‘ula means “red”), the Hawaiian coot (‘alae ke‘oke or ‘alae kea) has a white bill (ke‘oke‘o and kea both mean “white”).
[Illustration: Hawaiian Coot]
The Hawaiian coot is about 14 to 15 inches (35 to 38 cm) long, and mostly dark gray to black on top, with white undertail feathers. The bill is ivory white, as is the bulbous frontal shield (or frontal knob), though rarely a bird will have a brown or red frontal shield.
Coots feed on insects, fish, and tadpoles as well as the leaves and seeds of aquatic plants. Coots don’t fly much but are able to sustain flight low to the water.
Coots may nest throughout the year, particularly between March and September, building a floating nest on wetland vegetation (e.g., in lo‘i kalo, or taro patches) using sedges, weeds, taro stems, grass, and other aquatic plants. The nest may rise and fall with water levels.
After building its nest, the coot lays usually from three to ten eggs (averaging four to six eggs). The creamy to tan-colored eggs are speckled with black and incubate for three to four weeks.
The coot chick is downy black with a reddish-orange neck, head, and bill and has a baldish appearance due to the absence of down on the crown and forehead. The chick’s reddish-orange bill has a black tip. Soon after hatching, the chicks are able to swim.
Historical records do not indicate there ever were a large number of coots, yet the bird was significant in Hawaiian mythology and some early accounts reported large populations on Kaua‘i. A 1982 count documented 700 coots, mostly on Kaua‘i, O‘ahu and Maui.
The Hawaiian coot is federally listed as an endangered species. There are currently an estimated 2,000 to 4,000 coots living throughout the main Hawaiian Islands, with likely few to none of the birds on Kaho‘olawe and Lāna‘i.
The largest coot populations are found on Kaua‘i, O‘ahu and Maui. Coots are currently listed as endangered on Hawai‘i Island, Maui, Lāna‘i, Moloka‘i, O‘ahu, and Kaua‘i. Coots are known to fly between the Hawaiian Islands.
[Photograph: Hawaiian Coot]
Hawaiian Duck (Anas wyvilliana)
Hawaiian Name: Koloa Maoli (“Native Duck”)
Status: Endangered Species. Found on Hawai‘i Island, O‘ahu, Kaua‘i; possibly extinct on Maui.
Male koloa are about 20 inches (51 cm) long while female koloa are about 17 inches (43 cm) long. Koloa are mottled golden brown in color, with a greenish head and olive-colored bill. Male koloa have a darker head than females, and some females have a bill with an orange tip.
The koloa’s secondary wing feathers (speculum) are greenish-blue to metallic purple in color, with white borders. The duck’s feet and legs are orange.
[Illustration: Hawaiian Duck]
Koloa eat insects, mollusks, and aquatic vegetation. Koloa breed and nest year round, particularly between December and May, beginning at about one year of age. The birds often nest near mountain streams and taro patches as well as near irrigation ditches, low elevation wetlands, and river mouth areas.
A well-hidden nest is built using feathers and down, and usually from two to ten white to tan-colored eggs are laid (the average clutch size is eight eggs). The koloa eggs incubate for about 28 days and then hatch. After about nine weeks the birds learn to fly.
Koloa are widely distributed on Kaua‘i, where more than 80% of all koloa are found. Once abundant on all of the main Hawaiian Islands except Lāna‘i and Kaho‘olawe, by 1915 koloa became rare on all of the Hawaiian Islands except Kaua‘i.
By 1947, an estimated 30 or fewer koloa were on O‘ahu and these birds were gone by 1960. In 1962 the World Wildlife Fund and the Federal Aid to Wildlife Restoration Act provided money for a bird restoration program. By 1979, more than 350 koloa had been released on O‘ahu and 300 more on the island of Hawai‘i.
The koloa’s population is now estimated at less than 2,500. More than 80% of all koloa are found on Kaua‘i. Some koloa have been relocated to O‘ahu and Hawai‘i Island.
The koloa was listed as a federally endangered species in 1967. The koloa is currently listed as endangered on Hawai‘i Island, O‘ahu, Kaua‘i, and listed as endangered and possibly extinct on Maui.
The koloa evolved from the common mallard (Anas platyrhynchos) into a unique Hawaiian species (not a subspecies). The common mallard is found in North America, Europe and Asia.
The endemic Hawaiian species closely resembles the female North American mallard. One threat to the koloa comes from interbreeding with domestic mallards, resulting in hybridization of the endemic Hawaiian species.
Two of the largest koloa populations in the Hawaiian Islands are found on the island of Kaua‘i, at the Hanalei Valley National Wildlife Refuge and the Alekoko (Menehune) Fishpond. These populations are also thought to be the least hybridized (and thus the most genetically pure). In addition to many other threats to this wetland species, koloa chicks may be eaten by dogs, cats, pigs, muskrats, rats, bass, and bullfrogs.
[Photograph: Koloa maoli]
Hawaiian Moorhen (Gallinula chloropus sandvicensis)
Also called: Hawaiian Gallinule or Mudhen
Hawaiian Name: ‘Alae ‘Ula (red forehead)
Status: Endangered Species. Found on O‘ahu and Kaua‘i; possibly extinct on Hawai‘i Island, Maui and Moloka‘i.
The moorhen is easily identified by its bright red frontal shield. Because the moorhen sometimes feeds out on the mud flats, it is also known as the mudhen.
Hawaiian legend tells of how the ‘alae ‘ula brought fire from the gods to the Hawaiian people. During the journey, the moorhen was scorched by the flames, giving the bird its red forehead, or frontal shield. The demigod Māui tried to catch the ‘alae ‘ula, “...in order to learn the secret of making fire...He caught them before they could hide and forced them to yield the secret of fire.”[i]
[Illustration: Hawaiian Moorhen]
The endemic Hawaiian moorhen (‘alae ‘ula) is a subspecies of North America’s common moorhen, also found in Eurasia. A non-migratory bird, the adult Hawaiian moorhen is about 13 inches (33 cm) long, with a black head and neck, and a slate-gray to bluish-black back, which may be somewhat iridescent. The flanks and undertail feathers are white.
The moorhen’s red bill has a yellow to light green tip. Aside from its red shield, the moorhen’s dark gray plumage looks very similar to the ‘alae ke‘oke‘o (Hawaiian coot, Fulica alai).
The moorhen’s feet are not webbed, and the bird’s yellowish-green legs and feet may show red near the top. Moorhen are adept at walking across floating wetland vegetation. An ancient Hawaiian proverb, “Hanopilo ka leo o ka ‘alae,” translates to “Hoarse is the voice of the mudhen,” and was said of someone “...who talks himself hoarse.”[ii]
Generally a shy and secretive bird, the moorhen likes to hide in dense cover, usually only coming out into the open in the morning and evening to feed. They inhabit wetlands, including freshwater marshes and lo‘i kalo (taro patches). Moorhen feed on aquatic plants (e.g., taro tops and young shoots), as well as animals, including mollusks and insects.
March through August is the main breeding period for moorhen, but they may breed year round. The moorhen’s courtship behaviors include bowing and arching as well as nibbling.
During breeding season the bird’s frontal shield may become enlarged and is also a deeper red color. When it comes time to nest, the moorhen will build a well-hidden nest, often on folded reeds, using plants and mud.
Moorhen lay from five to nine cream-colored eggs (which are spotted with grey, black and brown). The eggs incubate for about 22 days. The downy moorhen chick has a bright red bill and pale yellow to brown body, and is able to swim soon after hatching. Immature (juvenile) moorhen are olive-brown to grayish-brown in color.
The moorhen, also called the Hawaiian gallinule or mudhen, is thought to have been quite common throughout the Hawaiian Islands in the 1800s until the population declined rapidly in the early and mid-1900s.
The Hawaiian moorhen was federally listed as endangered in 1967 and remains an endangered species today. The moorhen is listed as endangered on O‘ahu and Kaua‘i, and endangered and possibly extinct on Maui, Hawai‘i Island, and Moloka‘i.
A 1982 count by the State Division of Forestry and Wildlife documented 194 moorhen on O‘ahu and Kaua‘i with perhaps a few scattered birds on Maui and Moloka‘i. In the 1970s and 1980s, aquaculture and taro cultivation created more suitable moorhen habitat, increasing the bird’s survival rate.
The moorhen’s secretive nature leads to uncertainty in current population estimates, which range from 150 to 900 birds left in the wild. Moorhen are found only on O‘ahu and Kaua‘i, with few to none on Maui and Moloka‘i and probably none on Hawai‘i Island.
Efforts to reintroduce moorhen on Hawai‘i Island and Maui have not been successful.
[Photograph: Hawaiian Moorhen]
Black-Crowned Night-Heron (Nycticorax nycticorax hoactli)
Hawaiian Name: ‘Auku‘u
Indigenous: American continent.
[Illustration: Black-Crowned Night-Heron]
The Black-crowned night-heron is about 25 inches (63 cm) long with a wingspan of almost 4 feet (1.2 m). The night-heron has yellow legs, and a black head, back and bill, but otherwise is mostly gray.
The birds are often seen standing motionless at the edges of lagoons, marshes, canefield ditches, lo‘i kalo (taro patches), ponds and exposed reef areas. The night-heron may be heard making a fairly loud “kwok” sound while flying.
When in breeding plumage, the male night-heron develops four or five long white head plumes, while the female may have just two or three. These white nuptial plumes grow out from the back (occipital) region of the bird’s head. Immature night-heron are streaked with white and brownish-rust colors that turn mostly gray as the bird matures.
An ancient Hawaiian proverb, “Kohā ka leo o ka ‘auku‘u,” translates to “The voice of the ‘auku‘u is heard to croak,” and referred to “...a snooping gossip. The ‘auku‘u bird lives in the upland and goes to the lowland for fish, often snatching them from people’s ponds.”[iii]
The Black-crowned night-heron feeds primarily on crustaceans and fish, but also eats mice, frogs, aquatic insects, and chicks of other bird species (e.g., Hawaiian Black-necked stilts, Brown noddies, Sooty terns).
The night-heron is a solitary wading bird. Looking for prey beneath the water, it is most active at dawn and dusk, and may feed during the night as well as during the day.
Black-crowned night-heron breeding occurs around May. Using large sticks and twigs, the night-heron constructs a nest in a tree and lays usually two to four bluish-green eggs. The Hawaiian Black-crowned night-heron is indistinguishable from the North American Black-crowned night-heron.
A Hawaiian chant to the ancient chief Kuali‘i mentions the ‘auku‘u, a bird that was once found on all the main Hawaiian Islands but today is much less common. Kuali‘i was a warrior chief known for his strength and bravery.
[Photograph: Black-Crowned Night-Heron]
Threats to Wetland Bird Species of the Hawaiian Islands
A primary threat to native wetland birds is the destruction of their habitat due to urbanization, diversion of water, and development.
Other threats to wetland birds include disease, parasites, deterioration of food quality and supply, and introduced species such as cats, dogs, pigs, rats, barn owls, mongoose, cattle egrets, and even bullfrogs (which may prey on small chicks).
Water contaminants, such as insecticides, heavy metals and petroleum products are also destructive to the survival of native wetland species. Introduced plants such as the mangrove and the water hyacinth also make habitat unsuitable for native birds.
The cattle egret, an introduced species, may prey on young native birds as well as compete for food resources. Introduced fish, such as tilapia, may also consume valuable food resources, affecting native bird populations.
For a more in-depth discussion of threats to native Hawaiian species, see Overview of Native and Polynesian-Introduced Species of the Hawaiian Islands, Chapter 5.
[i] p. 310, Pukui, Mary Kawena. ‘Ōlelo No‘eau: Hawaiian Proverbs & Poetical Sayings. Honolulu: Bishop Museum Press, 1983. Proverb 2830.
[ii] p. 57, Pukui, Mary Kawena. ‘Ōlelo No‘eau: Hawaiian Proverbs & Poetical Sayings. Honolulu: Bishop Museum Press, 1983. Proverb 472.
[iii] p. 194, Pukui, Mary Kawena. ‘Ōlelo No‘eau: Hawaiian Proverbs & Poetical Sayings. Honolulu: Bishop Museum Press, 1983. Proverb 1812.