How Do Native Hawaiian Birds Survive in a Fragmented Forest?

August 18, 2011
Jennifer Donovan

When humans cohabit with Mother Nature, they tend to leave footprints behind. They fragment the natural forest landscape into patches of trees and other vegetation separated by the diverse products of their labors—agriculture, residential development, industry. Even well-intentioned efforts at forest management can wind up fragmenting otherwise contiguous forests.  Because many wildlife species evolved in large blocks of contiguous forest, they can be harmed when human activities break up landscapes into a patchwork of smaller isolated pieces of habitat.

Sometimes Mother Nature causes fragmentation herself. When volcanoes erupt on forested hillsides, for example, lava flows divide the forest into patches of trees separated by lava rock. On the Big Island of Hawaii, lava flows have created more than 300 isolated forest fragments.  Native Hawaiians call these patches of forest kipukas.

David Flaspohler, a professor in the School of Forest Resources and Environmental Science at Michigan Technological University, went to Hawaii this year to help find out how the birds that live in the kipukas manage to survive.  He is part of a multi-disciplinary team of scientists from Stanford University, the University of Maryland, the Carnegie Institution for Science, the US Forest Service Institute for Pacific Islands Forestry and Michigan Tech. They were funded by the National Science Foundation (NSF) to study the effects of Hawaii’s kipukas on the creatures that inhabit them.  The five-year $1.2 million study will continue through 2015.

Formed by lava flows through the forests on the slopes of Mauna Loa in the 1850s, the kipukas range from ¼ acre to 150 acres in a remote, protected area where mankind’s footprint is minimal. Kipukas are home to native vegetation, insects, rare birds and rats introduced by man.  This relatively simple forest ecosystem presents an ideal living laboratory that allows 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 explains.  “Here we can examine the ecological legacy of a century and a half of fragmentation; that is extraordinary.”

A conservation biologist, Flaspohler’s research focuses on how organisms interact with their environment, particularly ecosystems altered by human activity and species that are most sensitive to such changes. The effect of forest fragmentation on the imperiled songbirds that live in the kipukas is one of Flaspohler’s particular interests.  

In a paper published last year in the journal Biological Conservation, Flaspohler and co-authors observed that the smaller kipukas were dominated by native birds, while the larger contiguous forests contained a higher proportion of non-native bird species.  “This is precisely the opposite pattern one finds in most temperate mainland forests, where exotic birds are favored by fragmentation,” he says.

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