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Searching for life in old “ocean of forest”

 

By Jennie Erin Smith

© The New York Times Co.

FLORENCIA, COLOMBIA » In June 1912, Leo Miller, a collector with the American Museum of Natural History, arrived in the Caquetá region of Colombia, where the eastern foothills of the Andes melt into the forested lowlands of the Amazon basin.

Miller was working for Frank Chapman, the celebrated curator of birds at the museum. Chapman suspected that Colombia’s wildly varied topography had given rise to an unusual density of species, and sent collectors like Miller to bring him birds from all corners of the country to study.

Miller set up camp on a farmstead called La Morelia, surrounded by what he described to his mentor as “a perfect ocean of forest stretching out ahead as far as the eye can see.” There, he and his Colombian assistants worked day and night, beleaguered by rain, malaria and insects. By the end of July, they had collected more than 800 birds for Chapman, who was thrilled.

On a morning in early August, a century and nine years after Miller loaded his specimens onto river rafts and commenced his return to New York, a group of researchers tramped through muddy fields to their base camp, a ranch in a rural outpost of the city of Florencia.

The team, led by Andrés Cuervo, an ornithologist at Universidad Nacional in Bogotá, has organized six expeditions across Colombia, collecting birds and data for comparison with Chapman’s; this was the fifth. The undertaking, called Alas, Cantos y Colores — Wings, Songs and Colors — is financed by the Colombian government, with the participation of research institutions in Colombia and the United States. Studies of species from the same place over long periods of time are rare in science, and this resurvey project stands to speak volumes about how tropical birds have responded to changes in land use and climate.

A lot has changed in this part of Caquetá since 1912. For one, the “ocean of forest” has been reduced, after decades of expanded cattle grazing, to mere islands in a sea of pasture. Before arriving, the researchers had pored through satellite images in the hope of finding a forest big enough to sustain the kind of bird life they sought. A patch adjacent to the farm was the best they could do.

This group comprised 10 Colombian biologists and one American. Half were women, most were in their 20s and 30s, and several lived and worked in the Caquetá region.

Importantly, the specimens they collected would not leave Colombia. Instead, they would be deposited in the public natural history collections of the Universidad Nacional. Ornithologists like Cuervo had spent much of their careers studying their own country’s birds in foreign museums. The young scientists on this trip, Cuervo hoped, would not have to.

Shades of green

The farm’s owners, the Alvira family, had sent their horses into the pasture and allowed the scientists to turn the stable into a lab. Plastic card tables held syringes, vials, glass slides, rulers, scalpels and a lot of forms and lists.

On the packed-earth floor sat a cooler with dry ice and a canister full of liquid nitrogen, which is needed to flash-freeze tissues for genetic studies. The supplies had arrived by tractor early that morning as the team made its hourlong hike from a nearby village. During the group’s previous expedition to a highland forest in southern Colombia, the nitrogen had tumbled off the back of a mule that slipped on the trail, but was saved before it could spill.

Outside in the forest, the team strung hundreds of feet of mist nets — loose, wispy netting that causes birds to become trapped in its pockets — as howler monkeys groaned from unseen perches. At two o’clock, Juliana Soto, a biologist with the Instituto Humboldt in Colombia, car- ried in the expedition’s first bird, labeled MOR-001 — MOR for Morelia — in a cotton bag hooked to a cord around her neck.

It was a male striolated manakin, with a little green puff of a body and a proud red crest. In Colombia, people tend to call this family of birds saltarines, or jumpers, for the way that males gather and hop from branch to branch to impress an audience of females.

In 1912, preparing birds for scientific study was a simpler process. Birds were shot in the field, with many never recovered. Soft tissues were discarded, and only skeletons and skins were conserved. Each body was dried, filled with cotton and tagged with information on who had collected the bird and the location and altitude of its capture.

The technical and ethical demands of modern science require that greater care be taken with each specimen. A few on this team were veteran ornithologists; others were students, volunteers and newly minted professionals still mastering the challenges of fieldwork. The more experienced members helped the rest.

Andrea Morales Rozo, who teaches biology at the Universidad de los Llanos in central Colombia, guided the team at the nets, from which she skillfully extricated birds unharmed. Morales Rozo has been studying the blackpoll warbler, a species that migrates between the Amazon and Canada; she was part of a group that recently compared museum specimens and fieldcaught birds and learned that the warbler’s northward range had shifted by nearly 400 miles in 45 years.

Cuervo, the expedition leader, offered calm, fatherly support to those at the processing table. It’s not always obvious how best to describe a bird’s colors, for example, and second opinions were often requested. Was a wing “verde café,” greenish brown? Or was it “verde olivazo,” olive green? Was a female bird’s brood patch, the bare skin that warms the eggs, still smooth or becoming wrinkly?

MOR-001 struggled in Soto’s hand as she passed it to her colleague, Jessica Díaz, a field biologist hired for the expeditions. The bird was photographed and logged. Díaz labored to extract a tiny amount of blood from its jugular vein with a syringe, expressing the drops into a vial of alcohol.

She then prepared herself to euthanize it with rapid cardiac compression, using fingers to apply firm pressure over the bird’s heart. With this technique, small birds pass out within seconds and die in about half a minute. Large birds are anesthetized.

Díaz held MOR-001 under the table so as not to have to watch; her colleagues did the same whenever their turn came to sacrifice a bird. “This is the notfun part,” she said, softly.

Each bird was wrapped tightly in plastic and placed on dry ice to await the next, more complex stages of dissection and preservation, which would occur at the university lab. By the time MOR001 was in the cooler, swathed like a miniature mummy, several more bags wriggled on a wire above the table, and the heat of the afternoon was breaking.

And no antbirds called

For long stretches of the next day, few birds came in. The researchers weren’t used to this; normally, they would be too busy to even eat. “Miller said in no location in Colombia did he do so well,” Soto lamented after one fruitless return from the nets.

A century earlier, Miller had brought back from this site a dozen varieties of antbirds, a family of insect-eating species that need the refuge of the darkness of thick tropical undergrowth.

Most people associate the Amazon region with showy macaws and toucans, but to an ornithologist, the diverse antbirds are among its main draws. In a large, uninterrupted tract of forest, “you get overwhelmed by antbirds, by many species calling at the same time,” Cuervo said.

But antbirds avoid sunlight. With the forest so exposed, and with so much light now reaching the forest floor, the team wondered whether they could capture any antbirds at all.

Before Cuervo and the rest of the group arrived, a small advance team had spent days conducting censuses of birds and bird song to better understand the composition of the local forest community. They heard no antbirds. They did hear the buzz of a chain saw.

Census data is an important component of these expeditions, complementing data gleaned from the specimens.

Last year, a group of Colombian ecologists successfully compared census data from one forest with Chapman’s specimens, and concluded that the composition of bird life had drastically changed over 100 years. In a forest that once favored specialized species, the all-purpose generalists now dominated.

“But if you’re asking what has changed within a species, you need the actual bird,” said Glenn Seeholzer, a research associate with the American Museum of Natural History who is part of the Colombia team. Species are not static; nor are bodies, behaviors or genes. Beaks grow or shrink over generations; feathers change in color or luster in response to different selective pressures. On a genetic level, the changes can be profound, revealing reduced or expanded diversity, an indicator of a population’s ability to adapt to changing environments.

Scientists are now able to extract some genetic material from old bird specimens by scraping the pads of the toes. By comparing data from birds collected on this trip with Chapman’s, “we will be able to see how the genetic variation has shifted,” Seeholzer said. “There are very few data sets for wild populations of birds that you could ask or answer these questions with.” Once this series of expeditions is complete, at the year’s end, the collections in both Bogotá and New York “will be much more valuable than the sum of their parts,” he said.

Several days at the Alvira farm, the team changed sites, striking a camp near a more promising patch of forest. Stands of rare palms and bamboo survived in this remnant, which bordered a wide, sandy river. The site was even closer to the old La Morelia estate, and on it they did better.

By the end of their time in Caquetá, they had collected some 400 birds representing more than 100 species. Ten were what they called focal species, which could be compared, morphologically and genetically, with birds in the Chapman collection.

It appeared — although the hard work to quantify this had yet to begin — that at least some of the bird life present in 1912 was still hanging on, even in vastly diminished habitats.

But many bird families were missing, among them the antbirds. The group left with just three, of a single species.



 

 

 

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