Male sparrows with cheating partners bring less food for offspring, study finds
When a cheating spouse upsets the sparrow love nest, it is the children who suffer, scientists have discovered.
Male sparrows whose mates are unfaithful bring home less food for their offspring, a study has shown.
Sparrows form monogamous one-to-one partnerships, but as humans well know, some marriages are more successful than others.
Many female sparrows are unfaithful and have offspring with other males. However, their infidelity comes at a cost, according to the new research.
Cuckolded males make the family pay by providing less food for their chicks than those with trustworthy partners, the findings reveal.
They seem to respond to suspected cheating rather than a recognition that not all the chicks in the nest are theirs.
Lead scientist Dr Julia Schroeder, from the Department of Life Sciences at Imperial College London, said: "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.
"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.
"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."
The team studied 200 male and 194 female sparrows on the island of Lundy in the Bristol Channel over 12 years, recording the DNA profile of every bird and tracking the family history of their hatchlings.
In this way the researchers were able to determine which females were the most unfaithful.
"Lundy is a unique natural laboratory because it is almost a closed system - very few birds leave the island or arrive from the mainland," said Dr Schroeder. "In the entire 12 years only four birds immigrated to Lundy, possibly carried by boat."
The research is published in the journal The American Naturalist.
Experts believe female sparrows tend to cheat with "fit" males of better genetic quality in order to have stronger offspring.