SPRING 2007/VOLUME 21, NUMBER 2
The Rainforest Home of the White-ruffed Manakin
In Costa Rica, an undergraduate seeks genetic clues to the consequences of deforestation
Tropical rainforests shouldn't be this cold, I thought as I pulled on a long-sleeved shirt in the darkness. The thick humidity was the only indication that a lush rainforest stood just beyond my fingertips, which I struggled to see in the darkness of my 3:30 a.m. wake-up time. Fighting grogginess, I flipped on my headlamp and joined my four companions for the steep ascent into the heart of the mountain forest. As we struggled up the muddy path laden with equipment, it felt like I slid one step back for every two steps I took forward. The swarms of insects I kept swallowing as I gasped for breath didn't help either.
I was part of an expedition to collect the first biological samples from the remote Guaymi Indigenous Reserve, one of the largest tracts of mid-elevation tropical forest in Costa Rica. Our team was led by Viviana Ruiz-Gutierrez, a Ph.D. student at the Cornell Lab of Ornithology and a native Costa Rican. Along with Viviana's three trusty Costa Rican field assistants, Jason, Michael, and Brayner, I rounded out our team of five. Our task was to capture and band understory forest birds in order to study how habitat fragmentation affects their populations.
I had come along for the summer 2006 field season to collect blood samples from the White-ruffed Manakin as part of my undergraduate honors thesis. I would later bring these DNA samples back to the Lab of Ornithology to analyze the bird's population genetic patterns using the advanced technology available in the Fuller Evolutionary Biology facility. This information would complement the many years of demographic data that Viviana and her advisor had been collecting on these birds.
Roughly the size of a chickadee, the adult male White-ruffed Manakin is glossy blue-black with a striking white bib on its throat; the females and juveniles are dull olive-green. While scouting the area the day before, I had heard many of the manakins' high, thin, rolling prreeet calls as foraging birds moved about in search of berries and insects.
When we finally reached our netting site deep within the forest, we divided our 20 nets between us and split off into the forest, deftly hanging the nets on bamboo poles we had set up the day before—all while hoping we didn't step on one of the supposedly numerous poisonous snakes that inhabited the area.
This spot within the Guaymi reserve was one of 10 forest banding sites that Viviana had set up throughout the mountain foothills of southwestern Costa Rica. All sites were between 3,000 and 4,000 feet in elevation, the source of the chill in the early morning air. Most of the other sites lay within small forest patches of less than half a square mile, but the 29-square-mile Guaymi reserve acted as a control site, a large and relatively undisturbed stretch of forest.
Deforestation is just one form of habitat loss and fragmentation—the leading causes of population declines and extinctions worldwide. In Costa Rica and much of Latin America, the conversion of forest land to cattle pastures, coffee plantations, banana farms, and other human use results in a mosaic of isolated forest patches surrounded by non-forest habitat. Many species of birds and other wildlife that depend on the sheltered interior of the forest may be unwilling or unable to cross the highly exposed stretches of pasture or agriculture that surround their forest homes. We are using demographic and genetic measures to assess the potentially disastrous effects that habitat fragmentation may be having on populations of forest birds.
All of this lab work and data analysis seemed very far away as we sat deep within the rapidly awakening forest, waiting to check the nets for the first time. The first few hours brought all sorts of birds—White-breasted Wood-Wren, Olive-striped Flycatcher, Golden-crowned Warbler, Chestnut-capped Brush-Finch, Bicolored Antbird, even a White-tipped Sicklebill—a stunning hummingbird with a strikingly curved bill. Viviana and Jason quickly banded and measured all of them.
When a White-ruffed Manakin came in, I carefully took a blood sample, then sent it on its way. We caught more manakins that morning than we had in any other single day. As I opened my hand and watched them fly away, I hoped that their small donation of DNA would help us understand and better conserve these tiny creatures and their beautiful forest homes.
Jacob Barnett is a Cornell undergraduate in the Lab's Fuller Evolutionary Biology Program.
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