Sanctuary in Paradise
On the slopes of Mauna Loa—one of the world’s most active volcanoes—Hawaiian honeycreepers make their home.
Thought to be descendents of a single species of finch that reached Hawaii millions of years ago, these rare songbirds are unique to the Pacific island chain. Since Polynesian and then European colonization of Hawaii, twenty-four of the forty-four known species have gone extinct, and nine of the remaining twenty are on the federal Endangered Species List. In fact, one third of all US listed birds are Hawaiian.
Honeycreepers not only survive in the fragmented forest caused by lava flows more than 150 years ago, some also seem to have found ways to thrive there.
David Flaspohler, a professor in the School of Forest Resources and Environmental Science, and Jessie Knowlton, a postdoctoral researcher in his lab, are trying to figure out why. What helps—or harms—these birds in the “kipukas,” a Hawaiian word for the forested patches created by lava flowing through densely treed land?
Funded by the National Science Foundation, the researchers are examining thirty-four kipukas ranging in size from one-quarter acre to 150 acres in a remote, protected area on the Big Island of Hawaii, where the human footprint has been minimal.
Kipukas are home to native vegetation, insects, rare birds like the honeycreepers, and rats introduced by man. This relatively simple forest ecosystem offers an ideal living laboratory, enabling scientists to study the interactions and adaptations of the creatures that call the forest fragments home.
“Most fragmentation studies look at species response to fragmentation over a few to maybe ten years,” Flaspohler says. “Here we can examine the ecological legacy of a century and a half of fragmentation.”
These forests are particularly important to the survival of native Hawaiian birds because they are above the 4,000-foot elevation threshold. Below that, introduced tropical mosquitoes carry introduced avian malaria, which has devastated native lowland bird populations.
A conservation biologist, Flaspohler studies how organisms interact with their environment, particularly ecosystems altered by human activity and species that are most sensitive to such changes.
“Honeycreepers are exquisitely suited to these dynamic native forests and the rich resources they provide, including nectar, insects, and seeds,” he says. “They survived millions of years of volcanism as a succession of islands rose and then eroded into the sea. In fact, these geologic forces were the engines that drove adaptive radiation, giving rise to the spectacular diversity of color and bill shape that make this group of birds one of the most famous in the world.”
Using delicate nylon mist nets designed especially for humane live capture and release of birds, Flaspohler and Knowlton gently capture the honeycreepers and band them. Each bird gets a uniquely colored combination of ankle bands so the scientists can identify them later. They have already banded more than 800 birds.
The impact of black rats on the honeycreepers’ survival is one of the scientists’ particular concerns. Not natives of Hawaii, the rats probably arrived on ships centuries ago. The tree-climbing rodents have become the most significant predator of birds and their eggs in the kipukas. Rats also eat insects, directly competing with birds for food.
Rats are being trapped and removed from half of the kipukas. The scientists will then compare the survival rate and abundance of the honeycreepers and the success of their nests in rat-infested kipukas and those that are virtually rat-free.
Flaspohler and Knowlton hope their research on the honeycreepers in the kipukas of Hawaii will teach us how to maintain biodiversity there and elsewhere in the face of increasing habitat fragmentation and climate change. Rising global temperatures are expected to allow malaria-carrying tropical mosquitoes to move upslope, threatening the birds in these forest refuges. “Hawaii can tell us how birds cope and evolve and persist, and these insights can inform our understanding of how birds cope with habitat change in other parts of the world,” he says. “This may help prevent more endangered species from becoming extinct.”
Their research is a collaborative effort with Stanford University, the University of Maryland, the US Forest Service Institute for Pacific Islands Forestry, and the Carnegie Institution.