Science Press Release

["Tim Avery" <tanager at timaverybirding dot com>]

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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