This video is called Butcher bird duet – again.
From Wired Science in the USA:
Finch Duets About More Than Getting the Girl
* By Brandon Keim
* August 9, 2010
Plenty of birds sing duets when they’ve only just met and are still trying to impress each other. But once they’ve mated, the singing stops. Or so scientists thought.
Zebra finches, at least, know how to keep the magic alive. Only after becoming a couple, in the intimacy of their nest, do they start singing to each other. That hasn’t been seen in other birds. Then again, maybe we’re just not looking.
“We had no idea that we would discover these private duets,” said Clementine Vignal, a sensory ecologist at France’s Université Jean Monnet. “Until now, only three to four percent of birds have been reported to duet. But we think that a lot of species may have been overlooked. These private duets may be common in monogamous speices.”
Curious about how zebra finches communicated in nature rather than a lab, Vignal’s team put microphones inside nest boxes made for wild birds. Duets were not on their mind; zebra finches don’t even duet during courtship, and only males sing songs. But they soon heard the birds exchanging synchronized clicks and trills (mp3), performed when one left or returned to the nest, or was nearby while the partner remained.
In laboratories, where male zebra finch songs make them a common model for studies on neural mechanisms of learning and mechanism, the birds are kept in small spaces with no predators and plenty of food. That may reduce the need for private duets, which Vignal’s team thinks are partly explained by a need to stay close and keep alert. But scientists may also have been blinded by an assumption that duets were purely a mechanism for advertising virility and reproductive health to would-be mates.
“Most of these studies have focused on display behaviors that characterize pair formation or mate choice — all these processes that interest people working on the evolutionary aspect of sexual selection. We forgot to think about what was going on after pair formation,” said Vignal. “If we record inside the nests of other really common species, like tits or blackbirds, I wouldn’t be surprised if we find these duets.”
Were the singers human, researchers might also explain the duets in terms of affection. Since they’re birds, the researchers describe the songs in terms of maintaining pair bonds, predator avoidance and conferred reproductive advantages. Vignal plans further studies of the duets, but thinks there’s more than reproductive imperatives in the tiny birds’ hearts and brains.
“They have emotions. They’re certainly different from the ones we accept, but they do have them,” said Vignal, who references studies on increasing levels of stress hormones in separated pairs. “We can imagine that this duet expresses some kind of emotion.”
Scientists have been able to predict the correct sequence of notes and “syllables” in the Bengalese finch’s melodious, but erratic songs: here.