HI ALL:
I thought someone might be interested in this???

Ian Paulsen
Bainbridge Island, WA, USA
ipaulsen at krl.org
A.K.A.: "Birdbooker"
"Rallidae all the way"

---------- Forwarded message ----------
Date: Sat, 9 Feb 2002 14:28:30 -0500
From: Jay Greenberg <conservationist at earthlink.net>
To: BIRDCHAT at listserv.arizona.edu
Subject: [BIRDCHAT] New Technique for Studying Migration

I thought birders might be interested in the following article which
was on ENS today. The entire article with photos can be viewed at
http://ens-news.com/ens/feb2002/2002L-02-08-06.html

I am also enclosing the abstract of the Science article.



--

Jay Greenberg <conservationist at earthlink.net>
Rochester, NY
------------------------------------------------------------------------

Feathered Clues Clear Up Migration Mystery

By Cat Lazaroff

WASHINGTON, DC, February 8, 2002 (ENS) - Using chemical clues extracted
from feathers, biologists have tracked down the wintering grounds of
tiny songbirds that migrate throughout the Western Hemisphere. The
findings will help conservationists identify and protect areas crucial
to the survival of migrating warblers, now threatened by deforestation
and other habitat changes. The study links the summer breeding grounds
of the black-throated blue warbler in eastern North America with its
wintering sites more than 1,000 miles away in the Caribbean, and helps
to identify where these migratory birds are most vulnerable.

Black-throated blue warblers belong to a group known as neotropical
migrant songbirds, many of which have shown dramatic decreases in
population in recent years. Researchers from Stanford University,
Dartmouth College and the Smithsonian Institution's National Museum of
Natural History analyzed minute chemical traces of carbon and hydrogen
in the feathers of black-throated blue warblers.

"Numerous migratory species that breed in the United States and Canada
are in decline," said C. Page Chamberlain, a Stanford professor of
geological and environmental sciences and coauthor of an article
appearing in today's issue of the journal "Science." "It is unclear,
however, whether these loses are due to problems in their breeding
grounds in the north or their wintering habitat in the Caribbean,"
Chamberlain added.

Central America, which plays winter host to as many as one-third of all
North American migrants, lost about 2.3 million acres of forest cover
per year between 1990 and 1995, according to the National Audubon
Society. Haiti and other Caribbean islands also have suffered widespread
deforestation, which conservationists suspect is partly responsible for
declining bird populations in Appalachia and other parts of North
America.

"To develop successful conservation strategies, you need to know where
the birds go in winter," Chamberlain explained. "Our study is the first
to link southern wintering and northern breeding populations of a
migrant bird."

Black-throated blue warblers and other migratory songbirds are
inherently difficult to track on a seasonal basis. "Biologists have
been banding warblers in the U.S. and Canada for 20 years, but only one
banded bird has ever been found in the Caribbean," said Dustin
Rubenstein, a Ph.D. student in ecology at Cornell University and lead
author of the study. Rubenstein analyzed feathers and developed the
statistical model used in the study while he was an undergraduate at
Dartmouth. Attempts at tracking warbler migrations with radio
transmitters or DNA sampling also have failed, Rubenstein added. "We
used the relatively new technique involving measurements of stable
isotopes to learn where specific groups of breeding birds spend their
winter," he said. "Ultimately, we hoped the results might help us
understand why some populations were declining."

In 1997, Chamberlain and collaborator Richard Holmes, a Dartmouth
biologist, helped pioneer a method of measuring carbon and hydrogen
isotopes that naturally accumulate in birds' feathers during long
migrations. The technique allows scientists in the lab identify breeding
sites of individual warblers.

Isotopes are atoms of the same element that contain different numbers of
neutrons. In nature, the most abundant carbon isotope is carbon 12,
whose nucleus is made up of six protons and six neutrons. A small
percentage of carbon atoms carry an extra neutron and therefore are
known as carbon 13. Hydrogen 1 (the most common hydrogen isotope) only
has one proton and no neutrons, but a rarer form, deuterium, contains
both a proton and neutron.

"The strength of isotope analysis is that you can use it to track whole
populations without injuring or killing individual animals," said Jacob
Waldbauer, a research associate in Stanford's Department of Geological
and Environmental Sciences, and a coauthor of the "Science" article.

When Chamberlain and his coworkers analyzed warbler feathers collected
at various U.S. and Canadian breeding grounds in 1997, they discovered
that the ratios of carbon 13 to carbon 12 and deuterium to hydrogen 1
gradually decreased as breeding sites moved north. For example, birds
nesting in Georgia had higher had higher amounts of carbon 13 and
deuterium in their feathers than those from Ontario, Canada, several
hundred miles to the north. Previous studies showed that isotope levels
in warbler feathers directly mirrored those found in the environment -
that is, the carbon 13 to carbon 12 ratio in plants and insects consumed
by warblers decreased in northern latitudes, as did the deuterium to
hydrogen 1 ratio in lakes and rivers.

"In most species of birds, feathers are renewed annually, and thus their
isotopic composition should reflect that of the foods and water consumed
at the time of feather growth," Chamberlain wrote.

For the current study, researchers collected feathers from almost 700
black-throated blue warblers. In North America, samples were obtained at
10 breeding sites - from Georgia in the south, to Michigan in the
northwest, to New Brunswick, Canada, in the northeast.

In the Caribbean, feathers were collected at 11 wintering locations on
four islands - Puerto Rico, Jamaica, Cuba and Hispanola, which is
divided between Haiti and the Dominican Republic. The results, wrote
the authors, were striking. Isotopic ratios in feathers collected in the
Caribbean decreased from Puerto Rico in the east to Cuba in the west,
indicating "that more birds from the northern portion of the breeding
range [Canada, Michigan, New York and New England] winter on the
westerly islands of Cuba and Jamaica, whereas more birds from the
southern portion of the breeding range [the Appalachian mountains from
Georgia to West Virginia] winter on the easterly islands of Hispanola
and Puerto Rico."

Understanding patterns of migration has important implications for
conservation of songbirds and other migratory species. "Breeding bird
survey data from the past 30 years indicate declines in black-throated
blue warbler abundance in the southern breeding areas - particularly the
southernmost extreme [Georgia and Virginia] - and little change, or even
increases, in abundance throughout much of the northern breeding range,"
the authors wrote. Furthermore, they wrote, the most extensive
deforestation in the Caribbean has occurred on the Haitian island of
Hispaniola, which may help explain the sharp population declines
observed in southern Appalachia. "Our results suggest a possible
connection between this and declines in the southern breeding population
of black-throated blue warblers," said Holmes. The study suggests that
bird conservationists in the U.S. may wish to focus their conservation
efforts a little further south.

"For the first time, we have evidence that it may be possible to restore
breeding populations in the north by preventing habitat loss in the
south, allowing us to develop an international conservation strategy for
dealing with songbirds," Chamberlain noted.

Isotope analysis is now being used on European warblers that winter in
Africa, Chamberlain noted, as well on salmon and other migratory
animals, and has even been used to trace the migration of cocaine from
Latin America to the United States.

------------------------------------------------------------------------

Linking Breeding and Wintering Ranges of a Migratory Songbird Using
Stable
Isotopes

D. R. Rubenstein,12* C. P. Chamberlain,2 R. T. Holmes,1 M. P. Ayres,1
J. R. Waldbauer,2 G. R. Graves,3 N. C. Tuross4

We used the natural abundance of stable isotopes (carbon and hydrogen)
in the feathers of a neotropical migrant songbird to
determine where birds from particular breeding areas spend the winter
and the extent to which breeding populations mix in winter
quarters. We show that most birds wintering on western Caribbean
islands come from the northern portion of the species' North
American breeding range, whereas those on more easterly islands are
primarily from southern breeding areas. Although segregated
by breeding latitude, birds within local wintering areas derive from a
wide range of breeding longitudes, indicating considerable
population mixing with respect to breeding longitude. These results
are useful for assessing the effects of wintering habitat loss on
breeding population abundances and for predicting whether the
demographic consequences will be concentrated or diffuse.

1 Department of Biological Sciences,
2 Department of Earth Sciences, Dartmouth College, Hanover, NH 03755,
USA.
3 Department of Systematic Biology,
4 National Museum of Natural History, Smithsonian Institution,
Washington, DC 20560, USA.
* Present address: Department of Neurobiology and Behavior, Cornell
University, Ithaca, NY 14853, USA.

To whom correspondence should be addressed. E-mail:
drr24 at cornell.edu

Present address: Department of Geological and Environmental
Sciences, Stanford University, Stanford, CA 94305, USA.

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