Washington: The idea of mating for life remains a romantic ideal but female birds act promiscuously because of certain long term benefits.
It`s all about having more grandkids. This is why female birds are promiscuous, says an Indiana University team.
In dark-eyed juncos, individuals sired by a male other than their mother`s bonded partner grew up to have higher reproductive success than did those whose mother stayed faithful, the journal Proceedings of the Royal Society B reports.
This study on a population of wild songbirds represents the first time that an individual`s paternity has been shown to affect its reproductive success as an adult, according to an Indiana statement.
"There are a lot of species that form monogamous social pairs but are decidedly promiscuous when it comes to mating and having offspring," says Indiana postdoctoral research associate Nicole Gerlach.
"What we`ve found is that, at least in juncos, these females are doing it for their kids, and for their kids` kids," Gerlach said of the work with Eleen Ketterson, Joel McGlothlin and Patricia Parker.
"In the long run, females are likely to have twice as many grandchildren if they mate with an extra-pair male than if they remain truly monogamous," added Gerlach.
Gerlach and colleagues conducted paternity tests on almost 2,200 nestlings that hatched between 1990 and 2007.
"Because we could look at these patterns over many years and many generations, we were able to find strong support for the idea that extra-pair mating by females does produce better offspring."