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
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