Featured Research

from universities, journals, and other organizations

Isotopes From Feathers Reveal Bird Migration

Date:
November 6, 2003
Source:
Geological Society Of America
Summary:
Using naturally occurring patterns of stable-isotopes created by weather and plants, Jason Duxbury of the University of Alberta and his colleagues are tracking the migration routes of birds of prey. Their work on the summer origins of migrating and wintering Peregrine Falcons and Burrowing Owls has shed new light on what has previously been the secret, non-breeding half of the birds' lives.

Using naturally occurring patterns of stable-isotopes created by weather and plants, Jason Duxbury of the University of Alberta and his colleagues are tracking the migration routes of birds of prey. Their work on the summer origins of migrating and wintering Peregrine Falcons and Burrowing Owls has shed new light on what has previously been the secret, non-breeding half of the birds' lives.

By analyzing stable isotopes of hydrogen, carbon, and nitrogen in bird feathers, Duxbury has been able to trace Burrowing Owls wintering grounds in southern Texas and central Mexico, as well as migrating Peregrine Falcons caught on the gulf coast of Texas, back to their breeding grounds in Canada.

The principle behind the work is simple: birds are what they eat. And what birds eat while growing feathers on the breeding grounds contains isotopes of hydrogen, carbon, and nitrogen. These vary in predictable patterns across North America.

Duxbury will be presenting a paper on his work on Wednesday, November 5, at the annual meeting of the Geological Society of America in Seattle, WA. Scientists there are exploring the evolving interface between isotope geochemistry and ecology.

Hydrogen and its heavier version, the isotope deuterium, are both naturally found in molecules of rain water. But as the cycle of evaporation and precipitation repeats across North America and over mountainous regions, the heavier deuterium isotopes get left behind. That creates well-mapped hydrogen/deuterium trends across the continent, Duxbury explains.

"There is a well known gradient of depleting deuterium/hydrogen ratios from the Gulf of Mexico and the Atlantic Ocean across the eastern part of North America," said Duxbury. As you get near mountains there is also a noticeable elevation effect that reflects how changes in elevation also cause precipitation cycles.

The hydrogen isotope signature of animals is essentially the isotope signature found in the water and food they eat. Furthermore, the isotope signature found at the bottom of the food chains can be passed up to the top of food chains. The result is that isotopic signatures in the feathers of the top predators reflect the area where the food was consumed while the feathers were grown.

Carbon isotopes, also found in feathers, vary with latitude due to different growing conditions for plants across the continent. Even nitrogen isotopes can help track birds, though nitrogen isotopes variations are not found in predictable patterns. The application of nitrogen-rich fertilizers in agricultural areas can also alter nitrogen isotope ratios, Duxbury explains.

To collect the feathers for analysis, Duxbury and his colleagues rely on other researchers across North America. "Since 1995 I've had other researchers who were banding birds gather feathers all across North America," Duxbury said.

In order to get a local isotope baseline for a bird population the researchers first gather feathers from nestlings at their nest sites. Then they gather feathers from birds on migration or on their wintering grounds to trace them back to the isotope baseline based on the nestlings.

In the case of Burrowing Owls, the stable isotope technique has traced unbanded owls wintering in central Mexico back to Canadian breeding populations, said Duxbury. Subsequent analyses have also revealed that Burrowing Owls disperse more widely between breeding seasons than previously thought. That discovery, in turn, can be applied to population models used in the conservation of Burrowing Owls.

This relatively new technique will not replace banding, says Duxbury, since it cannot trace a bird to an exact location. However, the recovery of a banded bird is very rare event, and so it takes decades to accumulate data. Stable-isotope analysis is providing similar dispersal and migration data, but at a far greater rate. In essence, every bird that is captured for a feather sample is equivalent to a band recovery, Duxbury says.

"Essentially, it's not as good as getting a band return, which gives you A to B," says Duxbury. "You can't say exactly where a bird's origin was, but you can narrow it down to a region. For instance, with an isotope signature we can get it back to southern Alberta, whereas a band can get it to an exact nest location."

Satellite telemetry is by far the most accurate method of tracking birds. However, it comes with a hefty price. In addition, technology has not developed satellite transmitters small enough for Burrowing Owls, says Duxbury.


Story Source:

The above story is based on materials provided by Geological Society Of America. Note: Materials may be edited for content and length.


Cite This Page:

Geological Society Of America. "Isotopes From Feathers Reveal Bird Migration." ScienceDaily. ScienceDaily, 6 November 2003. <www.sciencedaily.com/releases/2003/11/031106051245.htm>.
Geological Society Of America. (2003, November 6). Isotopes From Feathers Reveal Bird Migration. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2003/11/031106051245.htm
Geological Society Of America. "Isotopes From Feathers Reveal Bird Migration." ScienceDaily. www.sciencedaily.com/releases/2003/11/031106051245.htm (accessed September 18, 2014).

Share This



More Plants & Animals News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Chimp Violence Study Renews Debate On Why They Kill

Chimp Violence Study Renews Debate On Why They Kill

Newsy (Sep. 17, 2014) The study weighs in on a debate over whether chimps are naturally violent or become that way due to human interference in the environment. Video provided by Newsy
Powered by NewsLook.com
Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins