For the first time biologists report 'irrefutable evidence' that tiny blackpoll warblers complete a nonstop flight from about 1,410 to 1,721 miles (2,270 to 2,770 km) in just two to three days
For more than 50 years, scientists had tantalizing clues suggesting that a tiny, boreal forest songbird known as the blackpoll warbler departs each fall from New England and eastern Canada to migrate nonstop in a direct line over the Atlantic Ocean toward South America, but proof was hard to come by.
Now, for the first time an international team of biologists report "irrefutable evidence" that the birds complete a nonstop flight ranging from about 1,410 to 1,721 miles (2,270 to 2,770 km) in just two to three days, making landfall somewhere in Puerto Rico, Cuba and the islands known as the Greater Antilles, from there going on to northern Venezuela and Columbia. Details of their study, which used light-level, or solar, geolocators, appear in the current issue of Biology Letters.
First author Bill DeLuca, an environmental conservation research fellow at the University of Massachusetts Amherst, with colleagues at the University of Guelph, Ontario, the Vermont Center for Ecostudies and other institutions, says, "For small songbirds, we are only just now beginning to understand the migratory routes that connect temperate breeding grounds to tropical wintering areas.
We're really excited to report that this is one of the longest nonstop overwater flights ever recorded for a songbird, and finally confirms what has long been believed to be one of the most extraordinary migratory feats on the planet."
While other birds, such as albatrosses, sandpipers and gulls are known for trans-oceanic flights, the blackpoll warbler is a forest dweller that migrates boldly where few of its relatives dare to travel. Most migratory songbirds that winter in South America take a less risky, continental route south through Mexico and Central America, the authors note. A water landing would be fatal to a warbler.
In the recent past, DeLuca explains, geolocators have been too large and heavy for use in studying songbird migration and the tiny blackpoll warbler, at around half an ounce (12 grams) or about as much as 12 business cards, was too small to carry even the smallest of traditional tracking instruments. Scientists had only ground observations and radar as tools.
But with recent advances in geolocator technology, they have become lighter and smaller. For this work, the researchers harnessed miniaturized geolocators about the size of a dime and weighing only 0.5g to the birds' lower backs like a tiny backpack. By retrieving these when the warblers returned to Canada and Vermont the following spring, then analyzing the data, DeLuca and colleagues could trace their migration routes.
For this work the scientists fitted geolocator packs on 20 birds in Vermont and 20 more in Nova Scotia. They were able to recapture three birds from the Vermont group and two from the Nova Scotia group for analyses.
So-called light-level geolocators use solar geolocation, a method used for centuries by mariners and explorers. It is based on the fact that day length varies with latitude while time of solar noon varies with longitude. So all the instrument needs to do is record the date and length of daylight, from which daily locations can then be inferred once the geolocator is recaptured. "When we accessed the locators, we saw the blackpolls' journey was indeed directly over the Atlantic. The distances travelled ranged from 2,270 to 2,770 kilometers," DeLuca says.
To prepare for the flight, the birds build up their fat stores, explains Canadian team leader Ryan Norris of the University of Guelph. "They eat as much as possible, in some cases doubling their body mass in fat so they can fly without needing food or water. For blackpolls, they don't have the option of failing or coming up a bit short. It's a fly-or-die journey that requires so much energy."
He adds, "These birds come back every spring very close to the same place they used in the previous breeding season, so with any luck you can catch them again. Of course there is high mortality among migrating songbirds on such a long journey, we believe only about half return."
Chris Rimmer, an ornithologist at the Vermont Center for Ecostudies notes, "We've only sampled this tiny part of their breeding range. We don't know what birds from Alaska do, for example. This may be one of the most abundant warblers in North America, but little is known about its distribution or ecology on the wintering grounds in Venezuela and the Amazon. However, there is no longer any doubt that the blackpoll undertakes one of the most audacious migrations of any bird on earth."
DeLuca says, "It was pretty thrilling to get the return birds back, because their migratory feat in itself is on the brink of impossibility. We worried that stacking one more tiny card against their success might result in them being unable to complete the migration. Many migratory songbirds, blackpolls included, are experiencing alarming population declines for a variety of reasons, if we can learn more about where these birds spend their time, particularly during the nonbreeding season, we can begin to examine and address what might be causing the declines."
As for why the blackpoll undertakes such a perilous journey while other species follow a longer but safer coastal route, the authors say that because migration is the most perilous part of a songbird's year, it may make sense to get it over with as quickly as possible. However, this and other questions remain to be studied.
Other researchers on the team besides those from UMass Amherst, the University of Guelph and the Vermont Center for Ecostudies, were from the Smithsonian Conservation Biology Institute, Acadia University, Bird Studies Canada and the University of Exeter, U.K. Each contributed to funding the study.
Janet Lathrop | EurekAlert!
Fine organic particles in the atmosphere are more often solid glass beads than liquid oil droplets
21.04.2017 | Max-Planck-Institut für Chemie
Study overturns seminal research about the developing nervous system
21.04.2017 | University of California - Los Angeles Health Sciences
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy