Tropical crooners sing when they're winning.
Football fans aren't the only ones to celebrate a win with a rousing song. Tropical birds called boubous do the same, a study has found.
The monogamous birds sing a special 'victory duet' after they have seen potential intruders off their patch, report Ulmar Grafe of the University of Würzburg and Johannes Bitz of the German Primate Centre in Göttingen, Germany, who studied the birds.
The researchers played recordings of four bird-song duets, which are often sung by boubous during contests over territory, to 18 different bird couples in Africa's Comoé National Park on the Ivory Coast.
Sixteen of the pairs stood their ground. Eleven of these 'winners' broke into their victory song shortly after the recording was turned off. Losers never sang at all1.
"The duet is clearly a post-conflict display," says Grafe. Boubous are extremely territorial - they probably sing to deter others from invading their patch, he says.
Tropical boubous (Laniarius aethiopicus) are shy birds that hide away in the dense forests and undergrowth of West Africa. They sing a range of duets, with males and females taking turns on lead vocals.
The victory duet is longer and louder than other songs. Some notes can be heard across two territories - an area the size of about 25 football pitches - and some refrains are repeated more than 40 times. This may serve as a warning signal to defeated birds and to other potential intruders from further afield, says Grafe.
Other duets may serve different functions, Grafe adds. They may help to cement the relationship or synchronize breeding.
Boubous aren't the only birds that sing when they're winning, says Peter Slater of St Andrews University, UK, who studies song duets in birds. "Pairs of geese stand there and make a fantastic honking noise after they've seen off a rival," he says.
Grafe, T. U. & Bitz, J. H. An acoustic postconflict display in the duetting tropical boubou (Laniarius aethiopicus): a signal of victory?. BMC Ecology, 4,, (2004).