A team of researchers filmed tiny songbirds rhythmically tapping their feet while singing to their mate.
Published in the journal Scientific Reports, the new study detailed a process so quick the unassisted eye cannot catch it. But thanks to high speed cameras, scientists can now watch it happen.
"The tap dancing is very fast and is completely invisible to the naked human eye," study senior author Masayo Soma, of Hokkaido University in Japan, told Discovery News. "Even a normal digital video camera cannot capture their motion, as the tapping is quicker than one frame."
For their research, the scientists observed the blue-capped cordonbleu and the red-cheeked cordonbleu, both of whom belong to the Uraeginthus genus.
"It wasn't very easy to record the behaviors because these birds are very choosy, and they only perform courtship displays to the individuals they like," Soma told BBC News. "We were so excited! It was really interesting. I just kept thinking, 'this could be a good paper.'"
Individual steps take place in fractions of a second - 20 milliseconds to be more precise. They typically come in blasts of three or four steps while the bird sings and also clutches a piece of nesting material in its beak while craning its neck and focusing its gaze on its partner.
"We already know that several non-passerine birds perform similar elaborate, multimodal duets, and that many passerines duet in song. What's new here is that there's a passerine species - a songbird - that is duetting in both song and dance," Will Allen, a behavioral ecologist at the University of Hull, told BBC News. "This study is an important first step, but we don't know whether the receiver prefers mates that display these dancing movements, or even that the receiver is sensitive to them. There are some suggestions here that they might, but without an experimental-type design, we can't work that out."
