Hawaiian Birds and Hawaiian Honeycreepers
Smithsonian scientists have determined the evolutionary family tree for one of the most strikingly diverse and endangered bird families in the world – the Hawaiian Honeycreepers. The researchers determined the types of finches that the honeycreeper family originally evolved from and also linked the timing of that rapid evolution to the formation of the main Hawaiian Islands. Using genetic data from 28 bird species that seemed similar to the honeycreepers morphologically, genetically or that shared geographic proximity, it was determined that the various honeycreeper species evolved from Eurasian rosefinches.
There were once more than 55 species of these colorful songbirds, and they are so diverse that historically it wasn’t even entirely clear that they were all part of the same group. Honeycreepers probably represent the most impressive example of an adaptive radiation in vertebrates that has led to a number of beak shapes unique among birds. Some eat seeds, some eat fruit, some eat snails, some eat nectar. Some have the bills of parrots, others of warblers, while some are finch-like and others have straight, thin bills.
Hawaii’s unusual geology played a role in the rapid evolution of many honeycreeper species that followed. The volcanic islands have formed one by one over time, as the Pacific tectonic plate is dragged across a “hot spot” of magma, and each new island provided a new opportunity for colonization. Each island that forms represents a blank slate for evolution, so as one honeycreeper species moves from one island to a new island, those birds encounter new habitat and ecological niches that may force them to adapt and branch off into distinct species.
The researchers looked at the evolution of the Hawaiian honeycreepers after the formation of Kauai-Niihau, Oahu, Maui-Nui and Hawaii. The largest burst of evolution into new species, called a radiation, occurred between 4 million and 2.5 million years ago, after Kauai-Niihau and Oahu formed but before the remaining two large islands existed, and resulted in the evolution of six of 10 distinct groups of species characterized by different sizes, shapes and colors.
Endangered Hawaiian Waterbirds Conservation
The Hawaiian Common Moorhen, Hawaiian Coot, and Hawaiian Black-necked Stilt have been listed under the Endangered Species Act for over 40 years, but these three endemic and endangered Hawaiian waterbirds are showing increasing populations. The three birds all reside exclusively in Hawai’i in low elevation wetlands. Their populations have been impacted by wetland loss, invasive plants, and introduced predators such as rats, cats, dogs, mongoose, and bull frogs. A study identified larger population increases on islands where wetlands were being protected (Oah’u and Kaua’i) and little or no population increases on islands containing few wetlands and/or less protection (Hawai’i and Maui).
The Hawaiian Coot (‘Alae Ke‘oke‘o) continues to be found on many of the larger islands and with a population estimate of up to 5,000, it is the most abundant of the three birds but it also has the most variable populations, year to year. Hunting depleted populations in the early 20th Century. It is 15 inches with a white bill topped by a frontal shield which is usually white, but can vary from bluish white to yellow to dark blood red. They have white undertail feathers that are seen when swimming or during their courtship displays.
The Hawaiian Black-necked Stilt (Ae’o) is found on Hawai’i, Kaua’i, Maui, Moloka’i, O’ahu, and Ni’ihau, and more recently, on Lana’i. Some reports indicate the bird was common in some locations in the late 1800s but by 1900 had become scarcer. By 1940, only 200 were believed to exist. The most recent survey estimates a population of about 1,500 birds. It is a slender wading bird that grows up to 15 inches in length, with a black back and white forehead, and white below; the female has a tinge of brown on its back. It has very long pink legs and a long black bill.
The Hawaiian Common Moorhen (‘Alae ‘Ula) population is the smallest of the three, numbering as few as 30 in 1970. The total current population is estimated to be in the low 100s. The bird historically inhabited all of the larger islands, but now inhabits only O’ahu and Kaua’i. The 13-inch-long moorhen is dark gray with a black head and neck, and white feathers on its flanks and on its undertail feathers. It has a very distinctive red frontal shield above its yellow-tipped bill. Its legs and feet are greenish.
Management actions are being implemented at places like Hanawi Natural Area Reserve on Maui, and Hakalau Forest National Wildlife Refuge on the island of Hawai’i. Given the long-term trend in the Hawaiian Islands of losing wetland habitat from unprotected areas, protected refuges and conservation easements on private land continue to be critically important to recovering the islands’ endangered waterbirds.
Hawaiian Birds and Nihoa Millerbird Relocation
Nihoa Millerbirds are endemic to Nihoa Island, where the population has dwindled to between 500 and 700. Two dozen endangered Nihoa Millerbird have been moved from Nihoa Island in the Northwestern Hawaiian Islands to Laysan Island 650 miles north in the hope they will establish a new population and prevent the extinction of the species.
The Nihoa Millerbird (Acrocephalus familiaris kingi), which weighs less than an ounce, is a lively brown song bird that forages for insects among low shrubs and bunch-grasses. Introduced domestic rabbits denuded Laysan’s vegetation between 1903 and 1923, drastically altering habitat and driving some endemic species, including Laysan Millerbird, Laysan Honeycreeper, and Laysan Rail, to extinction.
A team of wildlife specialists arrived by boat, captured birds at Nihoa and selected one dozen males and one dozen females for transport to Laysan. The birds were loaded onto a research vessel for a three-day boat trip to Laysan Island, where researchers believe the birds face no imminent threats and are suited for the ecosystem. Each bird carries a unique combination of colored leg bands to allow identification in the field, and half the birds were fitted with temporary radio transmitters so that their locations can be determined during their first three weeks in their new home.
The birds were released to their new home, and quickly began feeding on flies and spiders. The males began singing loudly to demarcate their territory to other males. The females, meanwhile, were observed fluttering their wings, which is a sign they’re interested in a male bird’s territory and the male bird. Biologists will remain on Laysan for the next year to monitor the birds’ movements, behaviors, and hopefully their first nesting attempts. On Laysan, the Millerbird joins other endangered species, such as the Laysan Finch, Laysan Duck, Hawaiian Monk Seal, and several plant species, as well as millions of nesting seabirds.
Hawaiian Birds and Nihoa Millerbird Conservation
The Nihoa Millerbird was originally confined entirely to Nihoa Island in Hawaiian Archipelago. Nihoa Millerbird is resident only on this uninhabited island refuge. Before its extinction, the Laysan Millerbird was resident only on Laysan Island. Their extinction between 1916 and 1923, was caused by human introduction of rabbits which destroyed the Millerbird’s habitat. Before vegetation was destroyed by rabbits on Laysan Island, the now extinct Laysan Millerbird was one of the most abundant of the 5 endemic birds. The Laysan Millerbird, Laysan Honeycreeper, and Laysan Rail are now extinct. The other 2 endemic birds still present are the Laysan Duck (Anas laysanensis) and Laysan Finch (Telespiza cantans).
When Nihoa Millerbirds were first discovered in 1923, the population was estimated to be 100 birds. The population size of the Nihoa Millerbird (Acrocephalus familiaris kingi) has fluctuated between 30 and 700 birds in the last 30 years, and the 2009 population estimate was 640. Threats include small population size, weather (drought, storms, hurricanes), variations in insect food supply, limited available habitat and nesting territories on the small island, introduced plants, animals, and fire. All these threats are very serious as this is the only place in the world where these birds can be found.
The Nihoa millerbird was listed as an endangered species in 1967 under the Federal Endangered Species Act. Nihoa is part of the Hawaiian Islands National Wildlife Refuge created in 1909 and the Papahānaumokuākea Marine National Monument, and access is restricted due to the island’s fragile ecosystem. For many years biologists have been considering the translocation of sufficient millerbirds to create a second population on another Hawaiian island to reduce the risk of extinction. Laysan Island is the first choice for this translocation effort, with a goal of doubling the population of this endangered bird through the translocation and creation of a second population on Laysan Island.
Hawaiian Birds and Nihoa Millerbird Breeding
The Nihoa Millerbird is only found on the Hawaiian Island of Nihoa in Papahanaumokuakea Marine National Monument. As name implies, Nihoa Millerbirds feed on all stages of Miller Moths. The main foods eaten also include other moths and caterpillars, insects, larvae, flies, grasshoppers, and small beetles. Nihoa Millerbirds frequently eat the bug Nysius, abundant on small shrub ‘aweoweo, flea beetles, numerous on popolo plants, and insects on ‘ilima bushes and the bunchgrass Eragrostis.
The Nihoa Millerbird (Acrocephalus familiaris kingi) has a metallic and bubbling voice. Male frequently sings, especially during breeding season. Their song has been described as thin, metallic, and energetic. However, songs of single-island endemics are usually rather simple and short, which is the case with Nihoa Millerbird. During breeding season, Nihoa Millerbirds sing loudly and continuously from tops of larger bushes, which are primarily ‘ilima, ‘aweoweo, and popolo. The female has a soft courtship vocalization.
Male singing is most frequent before and during initial nest construction and may erect crown and chin-feathers during bouts of singing or courtship feeding. Nesting may occur anytime between January and May, and takes less than two weeks. Both sexes of Nihoa Millerbird build nest. The male spends more time gathering material and the female brings less nest material but spends longer putting it into nest. Their cup nest is composed of dead grass fine rootlets, twigs, dried grass stems and blades, and down feathers. An average clutch contains two eggs. Both sexes generally alternate incubation, and chicks are fed directly by both parents.
Hawaiian Birds and Nihoa Millerbird
The Nihoa Millerbird is endemic to the remote island of Nihoa in Papahanaumokuakea Marine National Monument. This tiny bird measuring approximately five inches in length that was discovered in 1923 on this small island of only 155 acres, of which less than 100 are vegetated, and the rest being rock or bare soil. Another subspecies once occurred on Laysan Island, where it went extinct in the early 20th century after the island was de-vegetated by introduced rabbits. The Laysan Millerbird, discovered first, was given its name because of its fondness for feeding on large miller moths. The Laysan and Nihoa Millerbirds are generally regarded as separate subspecies.
The Nihoa Millerbird (Acrocephalus familiaris kingi) is a small reed-warbler, dark olive and olive brown above with grayish margins on feathers. They are whitish below with some grayish olive wash on sides and buffy brown flanks. The sexes are similar, with the females being slightly smaller. On the ground, they hop rather than run, and prefer dense cover near the ground, especially ‘aweoweo and ‘ilima.
Nihoa Island is steep and rocky, with steep cliffs on three of the island’s four sides rising out of the sea to 900 feet. Access to the Nihoa Millerbird is limited not only by the remoteness of Nihoa Island and required access permits, but also by the difficulty of landing on this steep, rocky island, often surrounded by rough seas. Although this endangered species has been somewhat protected by limited and difficult access, these restrictions also have limited research on its natural history. Research is also curtailed by justifiable concerns about the negative impact of even minimal human activities on the seabird colonies, as well as its numerous endemic plants and invertebrates. Millerbird population estimates since the 1960s have ranged from 31 to 731. Photo by Jack Jeffrey.
