The Endless Mating Game of Barn Swallows
The Endless Mating Game of Barn Swallows
Female barn swallows continue their “love hunt” even after pairing up. They’re not looking for a reliable food provider or a faithful mate; instead, they seek out the most attractive males, according to a study by researchers at Cornell University, New York.
“The bad news for male barn swallows is that the mating game never truly ends,” said Rebecca Safran, the study’s lead researcher. “It’s similar to what most humans do – constantly considering how much time and effort to invest in appearance and social status, even after a stable relationship has been established,” she added.
For barn swallows (Hirundo rustica erythrogaster), attractiveness is signified by a deep red chest and belly. If a male’s chest isn’t as dark as others, the female is likely to secretly mate with another male. Some unlucky males even end up raising an entire brood that isn’t their own.
In their experiment, Safran and her team allowed 30 pairs of barn swallows to mate naturally and lay eggs. They then removed the eggs, prompting the birds to mate again, and tested the eggs to identify their parents. Before the second round of mate selection, Safran photographed the males and marked their necks, chests, and bellies with red paint to enhance their appearance, while others were left with clear markings to rule out any influence from smell or other factors.
The researchers then allowed the pairs to breed again and conducted DNA tests on the chicks. The results showed that all the female barn swallows maintained their primary partnership with their original mates but secretly mated with other males. Males with enhanced red markings fathered more chicks compared to the first mating round. Those with unchanged coloring fathered the same or fewer chicks compared to the previous brood.
Ornithologists believe that feather coloration reflects the overall health of the male birds and the quality of their offspring. For females, it serves as a key indicator for selecting the best mate.
