David J. Flaspohler, an avian ecologist and conservation biologist at Michigan Technological University, writes from Hawaii, where he is studying the influence of human activities on birds and the natural ecosystems that support them.
Thursday, May 17
After six months back at the Michigan Technological University in the Upper Peninsula of Michigan, I am once again hiking across the sun-baked landscape of undulating lava on the Big Island of Hawaii, approaching one of the forest islands known to native Hawaiians as a kipuka. I hear a familiar and predictable sequence of bird songs. First, there?s the up-and-down whistle and staccato ending of the apapane as they fly above me from ohia flower to ohia flower in search of nectar. Next, there?s the nasal whine and rapid ?sound effects? of the fruit-eating omao, which sounds like someone in the forest tuning an old-fashioned radio.
Now, as I near the kipuka, I hear the discordant, chattery whistles of an i?iwi, a sickle-billed bird the color of a ripe persimmon ? a frequent poster child for imperiled Hawaiian birds. Entering the cool shade of the kipuka from the lava field, I am once again surrounded by the chorus of these and other birds, including the Japanese white-eye, a nonnative species imported from Asia in 1929 to control insect pests.
This is a large kipuka, so it may be home to the Hawaii elepaio, an endemic flycatcher with an explosive, cheerful song. Its nearest ancestors also came from Asia millions of years ago, without human help. When I hear the simple bouncy song of another endemic bird, the Hawaii amakihi, sounding a little like a black-and-white warbler from back home in Michigan, the chorus is complete. Now, finally deep inside the kipuka, I close my eyes and let this soundscape ring around me.
I?ve been studying the birds of these kipuka (in Hawaiian, the singular and plural of kipuka are the same) for several years on a five-year collaborative research project supported by the National Science Foundation. I am here only briefly this spring, to meet with the project postdoc, Jessie Knowlton, and the other investigators: Tad Fukami of Stanford; Christian Giardina of the United States Forest Service Institute of Pacific Islands Forestry; and Dan Gruner of the University of Maryland. I?m also here to spend time catching and banding birds, finding and monitoring nests, and continuing efforts to understand how this unique system of naturally fragmented forest patches supports its community of native birds.
I do not take the chorus that welcomed me for granted. Most United States birds on the endangered species list live here in this one small state, and many have gone extinct during the last century. Three years ago in New Zealand, I heard what a world without songbirds sounds like. In a grim realization that predates Rachel Carson?s ?Silent Spring? by several centuries, that isolated set of islands in the southern Pacific Ocean lost many of its native birds to introduced mammal species, Homo sapiens among them. After millions of years of bird song, many New Zealand forests grew silent.
Yet this morning, almost halfway up the slopes of the volcano Mauna Loa, the sun rises pink and lavender over the Pacific below, and the dawn chorus, on cue from the sun, rings down from the canopy above. I hear the songs that have been sung across this island chain for five million years or more. This morning, once again, I feel privileged to be among those who have heard it.
Previously, I researched the effects of forest clear-cutting in the Great Lakes region on birds nesting in an adjacent intact forest. Since then, I have been fascinated by how human-created habitat fragmentation influences birds. If an alien species hovering over our planet in space were to identify a single signature of modern humans, our modus operandi, it would be fragmentation. Wherever humans go in numbers, they leave behind habitats bisected by roads, chopped up by residential development and isolated by an ever-expanding population.
When formerly contiguous patches of habitat are broken apart and separated by some other habitat, it is called fragmentation. The species that remain often face new challenges that result from this process. Compared to individuals in formerly intact habitats, those in fragments may experience reduced survival and reproductive success, obstacles to dispersal and movement, and interactions with new species favored by fragmentation.
Here on the slopes of Mauna Loa, the kipuka were once part of a vast apron of forest until volcanic eruptions in the mid-1800s. The eruptions sent fingers of lava down the volcano and left a network of dozens of forest patches, some as small 50 by 50 feet, others larger than a 40-acre parcel. In these forest fragments, or kipuka, we can study something very rare: the long-term effects of natural forest fragmentation on an imperiled bird community. We have even begun to conduct some manipulative experiments, removing rats from some kipuka and leaving them in others, to monitor how food webs and birds respond.
Through this research, we hope to understand how native species in this forest survive in the face of introduced species like rats and mongoose, introduced diseases like avian malaria and environmental challenges like climate change.
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