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A crew of scientists in two boats eagerly scans the skies just off a piece of land located in the middle reaches of Rio Negro, Brazil. Against a background of lavender and golden clouds at dusk, the crown of a macarecuia tree hangs in fist-sized pods. Like other trees nearby, macarecuia tolerates seasonal flooding of rivers. Known locally as Ilha do Comaru, the island is submerged each March, leaving only the tree crowns above the water.
A handful of Purple Martins flit about, cutting through the heavy air with their notched tails and angular wings. Flocks of birds then gather together to form bird clouds, and the ferocious movements of birds are like Brownian motion particles. Suddenly a swarm forms a synchronous vortex. With a call, the birds drop into the crepuscular horizon like a shower of black sleet, descending into the canopy just a few feet from the boat. More birds rain down, covering the trees and making loud calls. In just a few minutes the spectacle was over and the sky remained static but the stars appeared.
The tiny island of only 12 acres (slightly larger than Yankee Stadium) is home to a large population of glittering swallows. With a concentration of about 250,000 birds from February to April, Purple his Martin’s roost is one of the largest ever discovered. However, its importance is not only due to its size, but also the important role the roost plays in the long-distance migration of birds. Scientists speculate that Komal could be a stopover or launch pad for many of his 9.3 million Purple Martins migrating from South America to North America.
Mario Kornhaft, an ornithologist at the National Amazon Institute in Manaus, believes the island is key to understanding the species’ steady decline. “This is the biggest opportunity to see what the Purple Martins are doing in South America in the winter,” he says. North American breeding populations are thought to have declined by 25% since 1966. In some areas the decline was even steeper, and in others the birds disappeared completely. Little is known about the challenges that the Purple Martins face as they make their way south each fall. “If you can track their movements, figure out what they eat, analyze if they’re contaminated with pesticides or other contaminants, then you know how they’re doing here. you can,” he says.
With binoculars slung over his shoulder, Kornhaft watches the bird’s restless silhouette. He is one of his twelve American and Brazilian scientists who have gathered here to observe and carry out Comal’s most extensive work to date. By taking a closer look at the birds crammed into this tiny island, we hope to glean insights that will help secure the future of the entire species.
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The arrival of the Purple Martins each spring is eagerly anticipated across North America. The bird’s breeding range extends from Canada to Mexico and consists primarily of the United States east of the Rocky Mountains. With the exception of small populations inhabiting the West Coast, the southern Rocky Mountains, and the deserts of the Southwest, they nest almost exclusively in structures that humans have built to welcome them, from hollowed gourds to miniature condominiums. increase. Birds often return year after year to the same garden or even the same Martin House. If they show up a little late, “our phone rings off the hook with people who are worried their baby won’t come back,” says Per, a nonprofit advocacy and research firm. Joe Siegrist of the Pullmartin Conservation Society says: organization.
This close relationship did not always exist. Natural cavities such as tree hollows once provided ample nesting grounds for Purple his Martin colonies. It’s a home for them to breed,” Siegrist says. As a result, the Purple Martin also became a valuable research subject. Thousands of people form bands each year. And these days, their loyalty to wild bird habitat makes them ideal for carrying tracking devices, many of which must be retrieved for information.
Purple martens have been extensively studied in North America, but scientific knowledge tapers off as they fly south. Purple martins are aerial insectivores that hunt insects with their wings. As such, it is the fastest declining bird group. (Insect populations are also declining due to factors such as pesticide use.) But the risk for birds is exacerbated by marathon travel.
Purple Martins have been seen on Amazon for a long time, but conventional wisdom thought they were just passing through Amazon. Some of the first evidence to the contrary came in 2007 when Bridget his Stachberry, a biologist at York University in Toronto, discovered the first songbirds (20 purples, his martins and his 14 thrushes). Received when equipping a geolocator. By measuring light levels, the device can locate birds within about 200 miles. Stachberry discovered that the following spring he had recovered two geolocators from Martins, one wintering in the Amazon and he had already wintered one further south.
Seven years later, Kevin Fraser, a postdoc at Stutchbury, now an ornithologist at the University of Manitoba, equipped 105 Purple Martins with a more sophisticated tracker, a GPS device that could place the birds to within about 30 feet. All but one of his loggers he recovered overwintered in the Amazon, and five spent a lot of time near Manaus, crammed into areas not as big as suburban residential areas. clarified that Siegrist, who works closely with Fraser, says this proved almost certainly that the birds were congregating in their roosts. If scientists can find it, they may begin to understand what role wintering grounds play in the survival of Purple Martins.
Siegrist and Fraser decided it was time to look around for themselves. They visited Manaus with his two colleagues in November 2016 and two years after him. They checked the places Fraser’s birds had visited, but found nothing. After all, their timing was off. They were 3 months early. They eventually also discovered that the birds had migrated their roosts from Papagaio Island, which Fraser had identified. “When they thought they knew where they were, they switched right away,” he says Siegrist.
Finally, in early 2019, Cohn-Haft heard from a student about a gigantic flock of birds that a local had shown her just 20 miles from Manaus. A guide named José Francisco dos Santos de Moraes runs his honky-tonk theme park featuring trained freshwater dolphins. Eyeing a new attraction, he began taking visitors when the herd arrived at dusk. Cohn-Haft quickly realized that it was the den of the Purple Martins. And he soon found the den to be a treasure trove of scientific data.
Me
An evening at the Flutuante Restaurante do Paulão (Big Paul’s Floating Restaurant), a short distance from Comal. Scientists rent the entire place as a cafeteria, dormitory, and laboratory. Sitting around the table where they had previously lunched with feijoada, Brazil’s national dish of pork and beans, they recall the comfort of just gathering purple martins: “Row a boat, like an apple tree.” You can pick it up from, ”he says Siegrist.
Now the captives hang in cotton sacks, hanging from a taut line like socks hanging to dry. Scientists remove feathered objects one at a time and pass them from person to person in a slow ornithological bucket of his brigade.
Ramiro Dario Melinski, a Brazilian research assistant at the Kornhaft Institute, wipes the bird’s mouth and cloaca with a cotton swab. He seals the sample in a pinkie-sized test tube and drops it into a thermos of liquid nitrogen. Genetic studies of material collected from birds were led by Erika Hingst-Zaher, a researcher at her Instituto Butantan in Brazil, and her collaborator, C. Loren Buck, a biologist at Northern Arizona University. Helps identify the pathogens they carry. Diseases, possibly exacerbated by exposure to toxic substances, may explain the decline in bird numbers.
Melinsky gave the bird to Clarissa Santos. Clarissa Santos was then a research assistant and is now a graduate student studying ecotoxicology at the University of São Paulo. She secures the band to her leg and gives it to Korn Haft.
Cornhaft holds the animal in its palm and gently blows away its shiny breast feathers. He scrutinizes the weight of his pectoral muscles. He spreads his wings like a poker hand. This bird has recently molted and its flight feathers are fresh. “They are all brand new,” he says. Flight feathers become tattered after use. This is fine for short trips, but taking an intercontinental trip with a worn feather is like driving cross-country with a bald tire. He declares the bird fit to leave for North America.
This is the third year Cohn-Haft and Siegrist have studied Martin at Comaru. They catch about 100 birds each time, and most of them seem ready to head north. Radio tags attached to birds in past seasons show that they stay for up to two weeks. I’m pretty sure that many individuals could pass through, and it could be closer to 1.5 million.
The fact that such a large portion of the world’s purple martens depends on a single site raises conservation concerns. There are currently no plans to dam the Rio Negro, but future hydroelectric dams could wash away roosts, for example. “That close concentration leaves them vulnerable,” he says Siegrist.
The work at Comaru may also have more global implications. Mercury from natural and man-made sources, such as artisanal mining operations, can be transformed into highly toxic forms in hydroelectric reservoirs and farm ponds and then migrate up the food chain to Purple Martins. His Hingst-Zaher and Buck, who joined Comaru’s team, are investigating whether mercury contamination affects the endocrine system of birds, reducing fat accumulation and making them less suitable for migration. Buck found mercury in the plumage of the North American Purple Martin. Samples from wintering grounds help determine the severity of the problem there. Martins contaminated in Brazil may not reach North America for research, he says:
The scientists hope the discoveries they make will help shed light on what’s behind the decline of other songbirds, especially other aerial insectivores. is likened to a canary in a coal mine. The ill-fated Purple Martin had to rely on the kindness of strangers to survive. But the bird’s adaptability and the comal’s discovery could play a leading role in saving its feathered brethren.
It’s around midnight before the researchers process the last bird. Two graduate students, trapped inside cloth bags, hoist everything off the line and cautiously board an aluminum boat. Cornhaft urges them to hurry. The birds need to go back to their roosts and get a good night’s rest. After all, they have a long journey ahead of them.
This story was supported by the Pulitzer Center. Originally published in the Fall 2022 issue as “Home Away From Home”.Become a member to receive the printed magazine donate today.
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