For female sparrows, infidelity comes with a cost -- the cheating female's partner will provide less food for their nest of young, says a study.Sparrows form pair bonds that are normally monogamous, but many females are unfaithful to their partner and have offspring with other males. But male sparrows can judge if a spouse is prone to infidelity, the study found.The research showed that males cannot actually identify whether all the chicks in their nest are theirs or not, and instead base their feeding decisions on who their female partner is."If chicks were switched into a nest where the female was faithful, then the father at that nest kept up his hard work providing for the chicks, suggesting they have no mechanism, such as smell, to determine which chicks are theirs," said lead researcher Julia Schroeder from Imperial College London."
Instead, the males may use cues from the female's behaviour during her fertile period -- for example how long she spends away from the nest," Schroeder explained.The study, published in the journal The American Naturalist, followed the entire sparrow population of the island of Lundy in the Bristol Channel in Britain for 12 years.The study followed 200 males and 194 females as they formed 313 unique monogamous pairs and hatched 863 broods on Lundy. Some sparrow 'divorces' occurred -- but most changes of life partner were due to death.The team DNA genotyped every sparrow, allowing them to build up precise family trees, and find out which females were most unfaithful and who their cheating males were. "Males changed their behaviour based on their partner. When they switched from a faithful partner to one prone to infidelity, they provided less food for their brood," Schroeder said.The researchers believe that females might also change their behaviour when paired with a less lazy male, cheating less with a more attentive father.