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, assistant professor and director of the Cornell Lab of Ornithology's
Source:Cornell University News Service