Revealed: the birds who play away from home

Female birds paired for life in apparently monogamous relationships seek out sex with other males in order to boost the genetic fitness of their offspring, scientists have discovered in a pioneering experiment involving warblers living on an island in the Seychelles.

Since the advent of DNA fingerprinting it has been possible to test the paternity of the offspring of seemingly monogamous species and, to the astonishment of scientists, many the offspring in such monogamous species appear to have been fathered by males other than the ones involved in rearing the brood.

The infidelity was inexplicable because only one male helps the female to raise the brood and the infidelity could result in him abandoning the nest.

This led scientists to suggest that perhaps the female was seeking better genes behind the back of her male partner in order to boost the genetic fitness of her offspring without the risk of losing the help of her male partner. Now scientists have found strong evidence in support of this hypothesis by studying in detail the lives and mating habits of 97 per cent of the warblers that live on the island of Cousin in the Seychelles, where the birds have been ringed and studied since 1997 by scientists led by David Richardson of the University of East Anglia.

The study, published in the journal Molecular Ecology, followed the fate of 160 birds hatched on the island between 1997 and 1999 over a period of 10 years. Although the birds appear to be monogamous in lifetime pairings, the females were found to have engaged in "extra-pair copulation".

The scientists found that the offspring of such female infidelity have a higher genetic diversity in crucial disease-detecting genes, known as the major histocompatibility complex (MHC), than would have been the case had they mated with their regular partner.

"We did not find any evidence for genetic benefits of extra-pair fertilisations per se, as on average extra-and within-pair offspring survived equally well. However, by not being faithful to a pair male with low MHC diversity, females are ensuring that their offspring do not end up with below-average levels of MHC diversity and therefore lower survival," Dr Richardson said.

Female warblers may be able to detect when their regular partner has a comparatively low genetic diversity, which leads them to stray to more highly diverse strangers.

Start your day with The Independent, sign up for daily news emails
PROMOTED VIDEO
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Sport
Ashley Barnes of Burnley scores their second goal
footballMan City vs Burnley match report
News
news
News
Sir James Dyson: 'Students must be inspired to take up the challenge of engineering'
i100
Life and Style
Apple showed no sign of losing its talent for product launches with the new, slightly larger iPhone 6 making headlines
techSecurity breaches and overhyped start-ups dominated a year in which very little changed (save the size of your phone)
Arts and Entertainment
Catherine (Sarah Lancashire) in Happy Valley ((C) Red Productions/Ben Blackall)
TV
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Sales Negotiator - OTE £24,000

£22000 - £24000 per annum: Recruitment Genius: An enthusiastic individual is r...

Recruitment Genius: Area Manager - West Midlands - OTE £35,000

£27000 - £30000 per annum: Recruitment Genius: An Area Manager is required to ...

Recruitment Genius: Area Manager - Yorkshire & Humber - OTE £35,000

£27000 - £30000 per annum: Recruitment Genius: An Area Manager is required to ...

Recruitment Genius: Embedded Linux Engineer - C / C++

£35000 - £45000 per annum: Recruitment Genius: A well funded smart home compan...

Day In a Page

A timely reminder of the bloody anniversary we all forgot

A timely reminder of the bloody anniversary we all forgot

Who remembers that this week we enter the 150th anniversary year of the end of the American Civil War, asks Robert Fisk
Homeless Veterans appeal: Former soldiers pay their respects to a friend who also served

Homeless Veterans appeal

Former soldiers pay their respects to a friend who also served
Downfall of Dustin 'Screech' Diamond, the 'Saved By The Bell' star charged with bar stabbing

Scarred by the bell

The downfall of the TV star charged with bar stabbing
Why 2014 was a year of technological let-downs

Why 2014 was a year of technological let-downs

Security breaches and overhyped start-ups dominated a year in which very little changed (save the size of your phone)
Cuba's golf revolution: But will the revolutionary nation take 'bourgeois' game to its heart?

Will revolutionary Cuba take 'bourgeois' golf to its heart?

Fidel Castro ridiculed the game – but now investment in leisure resort projects is welcome
The Locked Room Mysteries: As a new collection of the genre’s best is published, its editor Otto Penzler explains the rules of engagement

The Locked Room Mysteries

As a new collection of the genre’s best is published, its editor explains the rules of engagement
Amy Adams on playing painter Margaret Keane in Tim Burton's Big Eyes

How I made myself Keane

Amy Adams hadn’t wanted to take the role of artist Margaret Keane, because she’d had enough of playing victims. But then she had a daughter, and saw the painter in a new light
Ed Richards: Parting view of Ofcom chief. . . we hate jokes on the disabled

Parting view of Ofcom chief... we hate jokes on the disabled

Bad language once got TV viewers irate, inciting calls to broadcasting switchboards. But now there is a worse offender, says retiring head of the media watchdog, Ed Richards
A look back at fashion in 2014: Wear in review

Wear in review

A look back at fashion in 2014
Ian Herbert: My 10 hopes for sport in 2015. Might just one of them happen?

Ian Herbert: My 10 hopes for sport in 2015

Might just one of them happen?
War with Isis: The West needs more than a White Knight

The West needs more than a White Knight

Despite billions spent on weapons, the US has not been able to counter Isis's gruesome tactics, says Patrick Cockburn
Return to Helmand: Private Davey Graham recalls the day he was shot by the Taliban

'The day I was shot by the Taliban'

Private Davey Graham was shot five times during an ambush in 2007 - it was the first, controversial photograph to show the dangers our soldiers faced in Helmand province
Revealed: the best and worst airlines for delays

Revealed: the best and worst airlines for delays

Many flyers are failing to claim compensation to which they are entitled, a new survey has found
The stories that defined 2014: From the Scottish independence referendum to the Ice Bucket Challenge, our writers voice their opinions

The stories that defined 2014

From the Scottish independence referendum to the Ice Bucket Challenge, our writers voice their opinions
Stoke-on-Trent becomes first British city to be classified as 'disaster resilient' by the United Nations

Disaster looming? Now you know where to head...

Which British city has become the first to be awarded special 'resilience' status by the UN?