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.

News
peopleFrankie Boyle responds to referendum result in characteristically offensive style
Arts and Entertainment
Friends is celebrating its 20th anniversary this year
tvSeries celebrates 20th anniversary
News
news
Life and Style
Jack Cooksey goes for the grand unveiling - moments before dropping his new iPhone 6 on the floor
iphone launch
PROMOTED VIDEO
News
ebooksAn unforgettable anthology of contemporary reportage
Arts and Entertainment
Liam Neeson said he wouldn't
tv

Liam Neeson's Downton dreams

Sport
Yaya Touré (left) and Bayern Munich’s Spanish defender Juan Bernat
football
Arts and Entertainment
A spell in the sun: Emma Stone and Colin Firth star in ‘Magic in the Moonlight’
filmReview: Magic In The Moonlight
Sport
A 'Sir Alex Feguson' tattoo
football

Arts and Entertainment
Ben Whishaw is replacing Colin Firth as the voice of Paddington Bear
tv

Thriller is set in the secret world of British espionage

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

Primary Supply Teacher - Loughborough

£90 - £120 per day: Randstad Education Leicester: Are you a Teacher looking fo...

Primary General Cover Teachers

Negotiable: Randstad Education Leicester: Are you a Newly Qualified Teacher lo...

Part Time Primary Teacher

£90 - £120 per day: Randstad Education Leicester: Part Time Primary TeacherOur...

Science Technician

£7 - £8 per hour: Randstad Education Cheshire: The Job:School Science Technici...

Day In a Page

Mystery of the Ground Zero wedding photo

A shot in the dark

Mystery of the wedding photo from Ground Zero
His life, the universe and everything

His life, the universe and everything

New biography sheds light on comic genius of Douglas Adams
Save us from small screen superheroes

Save us from small screen superheroes

Shows like Agents of S.H.I.E.L.D are little more than marketing tools
Reach for the skies

Reach for the skies

From pools to football pitches, rooftop living is looking up
These are the 12 best hotel spas in the UK

12 best hotel spas in the UK

Some hotels go all out on facilities; others stand out for the sheer quality of treatments
These Iranian-controlled Shia militias used to specialise in killing American soldiers. Now they are fighting Isis, backed up by US airstrikes

Widespread fear of Isis is producing strange bedfellows

Iranian-controlled Shia militias that used to kill American soldiers are now fighting Isis, helped by US airstrikes
Topshop goes part Athena poster, part last spring Prada

Topshop goes part Athena poster, part last spring Prada

Shoppers don't come to Topshop for the unique
How to make a Lego masterpiece

How to make a Lego masterpiece

Toy breaks out of the nursery and heads for the gallery
Meet the ‘Endies’ – city dwellers who are too poor to have fun

Meet the ‘Endies’ – city dwellers who are too poor to have fun

Urbanites are cursed with an acronym pointing to Employed but No Disposable Income or Savings
Paisley’s decision to make peace with IRA enemies might remind the Arabs of Sadat

Ian Paisley’s decision to make peace with his IRA enemies

His Save Ulster from Sodomy campaign would surely have been supported by many a Sunni imam
'She was a singer, a superstar, an addict, but to me, her mother, she is simply Amy'

'She was a singer, a superstar, an addict, but to me, her mother, she is simply Amy'

Exclusive extract from Janis Winehouse's poignant new memoir
Is this the role to win Cumberbatch an Oscar?

Is this the role to win Cumberbatch an Oscar?

The Imitation Game, film review
England and Roy Hodgson take a joint step towards redemption in Basel

England and Hodgson take a joint step towards redemption

Welbeck double puts England on the road to Euro 2016
Relatives fight over Vivian Maier’s rare photos

Relatives fight over Vivian Maier’s rare photos

Pictures removed from public view as courts decide ownership
‘Fashion has to be fun. It’s a big business, not a cure for cancer’

‘Fashion has to be fun. It’s a big business, not a cure for cancer’

Donatella Versace at New York Fashion Week