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.
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.
Hawaiian Bird Photographer Jack Jeffrey
Jack Jeffrey has been studying and photographing Hawaii’s endemic birds for over thirty years. As a long time resident of the Big Island, a wildlife biologist, and a photographer, Jack Jeffrey, is intimately familiar with Hawaii’s hidden valleys, remote rain forests and rare birds. He combines a naturalist’s curiosity with a photographer’s patience and technical skill to produce beautiful images. Photographing Hawaii’s native forest birds in the wild is no easy matter. For some species, with very small populations, seeing the bird is next to impossible, never mind trying photographing it.
Publications that have featured his work include: Audubon Magazine, Smithsonian, Life, Natural History, Birders World, National Wildlife, Pacific Discovery, Defenders of Wildlife, Science, National Park, the National Geographic Canon Endangered Species Series, as well as numerous books, and calendars.
“Many of Hawaii’s birds are on the brink of extinction. I’d hate to think that I’m only recording images of these magnificent creatures for posterity. I’d rather believe that through my photography, I am providing an emotional link between humanity and the birds. If I do what I love… my passion…I feel that I’m doing my best to ensure that Hawaii’s people, and visitors from around the world, will continue to have opportunities to enjoy these colorful forest treasures for many generations to come.”
Hawaiian Birds and ‘O’u Conservation
The ‘O’u is a Hawaiian Honeycreeper that has been federally listed as endangered since 1967. With the last published sighting on Kauai in 1989, it is now quite possibly extinct. Distribution has been shrinking since 1900s, disappearing from Oahu by 1899, Maui by 1901, Molokai by 1907, and Lanai by 1931. On Kauai and Hawaii, ‘O’u (Psittirostra psittacea) are thought to persist in a fraction of its former range. Their range has contracted from low-elevation habitat since the first specimens were collected near sea level in 1779. The most recent range estimate is high elevation forests on windward Hawaii and in the Alaka‘i Swamp on Kauai.
Hurricanes such as ‘Iwa (1982) and ‘Iniki (1992), which struck Kauai, can eliminate all fruit and foliage in certain areas, causing widespread starvation or movement to lower elevations, thus resulting in exposure to avian disease. Introduced avian diseases are widely considered one of foremost causes of forest bird extinction in Hawaiian Islands. Introduced mosquitoes transmit avian malaria that is limiting populations of low-elevation native birds.
Feral house cats and rats are known to depredate ‘O’u and other Hawaiian forest bird populations through nest predation. Birds that may have preyed on ‘O’u include a bird-eating owl (Grallistrix auceps), the Hawaiian Hawk (Buteo solitarius), Short-eared Owl (Asio flammeus sandwichensis) and the introduced Barn Owl (Tyto alba).
Hawaiian Birds and ‘O’u Breeding
The preferred habitat of the ‘O’u on Kauai is a wet, dense ‘ohi‘a and ‘olapa dominated forest with native understory and dense growth. Hurricanes severely damaged large areas of Alaka‘i Swamp in 1982 and 1992, blowing down large trees and opening up the canopy. ‘O’u move up and down in elevation to exploit various native and introduced foods. Native fruits include those of various lobelioids, ‘olapa, mamaki, kawa‘u, alani, ‘ohi‘a ha, and a preference for fruits from ‘ie‘ie vine. Their bill is adapted for foraging on ‘ie‘ie, with a longer upper mandible that curves over tip of lower mandible, so they can thrust their bill deeply into inflorescence and extract component parts. Introduced fruits include mountain apple, guava, banana, peach, orange, and paper mulberry. They also forage on kukui, ‘ohi‘a nectar, and caterpillars.
The song of the ‘O’u is a repetitious series of whistles and trills, preceded by 3 to 4 loud, clearly whistled notes. The syllables of song are clear whistles of varying length including upslurred, downslurred, and even-pitched whistles of various frequencies. Each syllable is usually repeated 2–5 times, and an occasional ascending, descending, or even-pitched trill is included.
Two types of calls: upslurred and downslurred. Upslurred call is more common. Downslurred call is a melancholic pure whistle of varying length. Upslurred call is a pure tonal whistle of variable length. The male sings occasionally throughout year, but singing peaks immediately before onset of breeding season. Vocal repertoire of most Hawaiian honeycreepers suggests that females produce whisper songs and other vocalizations. Most male Hawaiian honeycreepers defend a moving territory around female, and songs or calls play an important role in this defense.
