Keeping track of Molokai’s rainforest birds.
[Appeared in the June 2, 2010 issue of The Molokai Dispatch]
By Catherine Cluett
Billowing mist drifts through moss-hung branches, and the air – cold and fresh – slips past your face like ghost fingers. It’s 7 a.m. and the rainforest oozes with life – from the imperceptible movement of a myriad bugs to the morning chatter of birds echoing through the forest canopy. It’s those birds that have brought experts from around the state to the Molokai Forest Preserve for a study that could determine future management tactics for Hawaii’s forests that are home to native species.
Sam Aruch cocks his head, listening to each bird call. His trained ears decipher and identify every whistle in the cacophony of chatter as he scribbles in a mist-moistened field notebook. He records what species he hears, as well as location and weather conditions.
Around the state, bird experts team up with local volunteers to study bird populations in conservation areas. Aruch works in resource management and was contracted by the Department of Land and Natural Resources Division of Forestry and Wildlife (DOFAW) to organize this year’s bird surveys.
The surveys, conducted in rotation around the state every fives years, serve as an assessment of current management of native bird habitats. They are also an important tool to help guide future management decisions, according to David Leonard, a wildlife biologist for DOFAW in charge of endangered forest bird programs.
Sipping the Nectar
Aruch keeps his ears tuned for two native species he expects to find on Molokai – the `apapane and the `amakihi. The `apapane has red plumage and sips nectar from `ohia lehua blossoms. Its calls and song patterns are varied, yet Aruch knows each one like his own voice.
The yellowish green feathers of the `amakihi make spotting this bird difficult, but its powerful voice reveals its presence in the forest.
A third native species, the endangered `i`iwi, or scarlet Hawaiian honeycreeper, persists only in small numbers. Richard Camp, project coordinator of the Hawaii Forest Bird Interagency Database Project, said he expects this year’s survey results to continue to show a decline in Molokai’s `i`iwi population.
Stopping at GPS-marked stations set 135 meters apart, Aruch pauses, pencil poised, to listen and look for eight minutes. Most identification is done by sound, but every once in a while, Aruch lifts his binoculars to catch a fleeting glimpse of feathers. Along the way, he replaces the flags and tags marking survey stations with fresh blue and pink flagging to last another five years.
Two more endemic species have not been seen since the 1960s and are presumed to be extinct, according to Camp: the olomao, or endemic thrush, and the kakawahie, or Molokai creeper. But Leonard said before the survey that even though these species seem to be gone forever, every new survey brings hope that they might be seen again.
While native birds are the focus of the study, much of what Aruch records are introduced species that have become more common than their native neighbors. The Red-billed Leiothrix – which Aruch describes as looking like a clown because of its red beak – is a shy bird but its warbling song brightens the dimly lit forest.
Two Japanese species – the Japanese Bush Warbler and the Japanese White-eye – are also common in the area. Aruch eloquently explains White-eye’s call as a “confused wandering chit-chat.”
Some stations are silent, with only crickets chirping faintly and the wind soughing through fern-covered branches. The pauses give time to appreciate the small, silent wonders of the forest – lacy, diminutive fern wahine noho mauna, or woman of the mountain, clinging to tree trunks; paper-thin ferns only one cell thick glowing in transparent emerald tones among brown-green moss; and dew-covered spider webs hung like ornaments among the foliage. Hawaiian lily plants abound, thriving in the absence of feral pigs for which they’re a delicacy.
“It’s nice to have to walk through the forest slowly,” explains Aruch. “I like coming back to the same areas and seeing how they change.”
Fighting the Plague
Disease resistance is key to native bird survival, and at relatively low elevations like the Molokai Forest Reserve, mosquitoes are rampant. Mosquitoes are the main culprit in the spread of avian malaria and other diseases that plague native bird species. Sighting birds at lower elevations is evidence of that species developing disease resistance, explains Camp. That means a potential increase in population.
While results of the 2010 Molokai bird survey will not be analyzed until the end of June, Camp said that initial sightings of both `apapane and `amakihi at lower elevations could point to a continued increase in population that he has noted over the past 10 years. `I`iwi are very susceptible to disease, but even so, their presence persists.
Aruch said that in addition to disease, habitat loss and introduced predators like cats and mongoose pose threats to the native bird population in Hawaii. The Nature Conservancy has taken steps to protect this habitat in the Kamakou Preserve by controlling goat and predatory populations, as well as working to eliminate feral pigs from the area that damage native vegetation and dig holes that fill with water for breeding mosquitoes.
Making It Happen
The bird surveys are the result of inter-agency cooperation, according to Aruch. He pairs up an expert in the field with someone who knows the island and it becomes a learning experience for all involved. The effort is spear-headed by DOFAW, while the United States Geological Survey (USGS) takes the raw data and processes it, and local agencies like The Nature Conservancy provide staff and terrain expertise.
It’s all part of the Hawaii Forest Bird Interagency Database Project, which collects information from many surveys completed over the past 25 years, standardizes the data, and compiles it to produce current population size estimates and trends, habitat models, and distribution maps for bird species in Hawaii. The database now contains records of over 400 studies that documented more than 800,000 birds.
The survey is completed using a variable circular plot method, a form of sampling that estimates the abundance of birds in a given area based on probability. Every time Aruch identified a bird by sight or sound, he would estimate its distance from where he stood. From that data, population density can be projected for a given area.
The area covered in about three days during the Molokai study is 10 square kilometers or about 2500 acres, according to Camp. The first Molokai survey was completed in 1979 and the last was done in 2004.
“Doing these surveys is always a challenge,” said Leonard. Working with the weather is the biggest hurdle in getting it done, he added.
Too much wind or rain can inhibit the ability to hear bird song. Transects also have to be completed in the morning hours, when birds are more vocal. In addition, proper completion of the surveys relies on close coordination between many agencies, as well as volunteers to make it happen.
Despite the challenges, a dedicated crew completed this year’s Molokai forest bird survey without a hitch. The data will contribute to a pool of information to model trends of native and non-native species around the state. And if all goes well, the `apanape will continue to sip `ohia nectar in the mist-shrouded upper reaches of the island for years to come.