From: "Tim Avery" <tanager at timaverybirding.com>
To: <birdtalk at utahbirds.org>

Thought many might enjoy this interesting release today, it involves a
Utah birder/scientist:

Looks count: If male barn swallows don't stay spiffy, the females cheat
in a jiffy

ITHACA, N.Y.  Even after they have paired with a male, the female
North
American barn swallow still comparison-shops for sexual partners. And
forget personality; the females judge males by their looks - the reddish

color of the males breast and belly feathers.

If the male's red breast is not as dark as other males in the
population, the female is more likely to leave him and then secretly
copulate with another male, according to a Cornell University study
featured on the cover of the journal Science (Sept. 30, 2005).

The bad news for male swallows is the mating game is never over, said
lead author Rebecca Safran, who conducted the study while a Cornell
postdoctoral researcher in ecology and evolutionary biology, and in the
Cornell Laboratory of Ornithology.

"It is dynamic and continual. This is something that most humans can
relate to  think of how much time and money we spend on our looks and

status long after we have established stable relationships."

Barn swallow (Hirundo rustica erythrogaster) males have a wash of
reddish-chestnut color from their throats to their bellies, and this
color varies among birds from very pale red-brown to a dark rusty-red.
Like many songbirds, half of all male barn swallows typically care for
at least one young chick that was actually fathered by another bird.

The researchers used this widespread phenomenon of cheating to test the
factors that may keep a female barn swallow faithful to her mate.
Sometimes males even rear an entire nest of illegitimate young.

After all pairs had laid their first set of eggs, Safran removed the
eggs so that the females would mate again. Before the females chose
their mates for their second nest, Safran captured the males and
randomly assigned them to one of three treatments. She either painted
their throats, breast and belly feathers with a red marker to enhance
their feathers to match the darkest  and most attractive  males in
the
population, or left them alone or painted them with a clear marker to
ensure that results were not biased by the coloring process. Then she
let the pairs breed again.

She conducted comparative DNA tests on the offspring from the first and
second nests. In the research, all 30 females remained socially paired
with their original male mate, but they were sexually active with other
males. The males with enhanced color fathered a substantially larger
percentage of offspring in their second nests. Males whose color was
unchanged fathered the same number or fewer chicks than they had in
their first nests.

"The study shows that the females are paying close attention to these
signals and that they respond quickly to changes in their mate's
appearance," said Safran. The reddish breast and belly feathers indicate

a male's quality, such as his health, status or ability to raise young,
Safran speculates.

The actual cue that female barn swallows use to assess potential mates
differ according to regional tastes. For example, classic studies have
shown that in the very closely related European barn swallow (H. rustica

rustica), males with long tail feathers attract more mates.

Although many previous studies have investigated mating patterns in
birds and other animals, this is the first study of its kind to
meticulously rule out biases such as age, size and initial variation in
signals of male quality, like coloration and to demonstrate that
mate-selection decisions are continual and dynamic. The results of the
study have implications for the evolution and upkeep of showy ornamental

traits  such as a peacock's tail or a deer's antlers  that are
costly
for males to maintain but give them an edge over rival males.

"If females are assessing mates on a day-to-day basis, it explains why
males continue to maintain costly ornaments even when they might appear
to have served their purpose," said co-author Irby Lovette, an assistant

professor and director of the Cornell Lab of Ornithology's Evolutionary
Biology program.

"Our goal is now to understand how certain males keep a better plumage
than others," said Kevin McGraw, Cornell Ph.D. R03, one of the
co-authors who is now an assistant professor at Arizona State University

in Tempe. "Factors like ultraviolet radiation from the sun, soiling and
even feather degrading bacteria are known to affect the color of bird
feathers once they are grown, and perhaps the best males are those who
spend more time preening and protecting their plumage."

The paper's other co-author is Colby Neuman, Cornell B.S. '05. In early
September, Safran began a new position as a postdoctoral researcher at
Princeton University. Supporters of the study included: the National
Science Foundation, the American Association of University Women, the
American Ornithologists Union, and the Animal Behavior Society.Good
BirdingTimhttp://www.timaverybirding.com
http://www.birdingwyoming.org
Salt Lake City, Utah
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