Songbirds can not only sing, but they can tap dance as well. A group of experts managed to film small songbirds that were rhythmically tapping their feet while crooning to a potential mate.

Species of the blue-capped cordon-bleu, Uraeginthus cyanocephalus, perform such rapid-fire footwork that the unassisted eye cannot see the movements, scientists said.

In a study featured in the journal Scientific Reports, researchers from Germany and Japan looked into the classic sexual selection theory where they say displays of complex multimodal courtship have evolved within species of blue-capped cordon-bleus.

Typically, male birds woo a female bird, and the female gets to choose her mate. With cordon-bleus, the female bird can also show displays of courtship by singing and tap dancing. These tap-dancing movements do not differ by gender, but per individual bird.

The team used a high-speed video camera to record the visual displays of these cordon-bleus. The researchers studied about 16 blue-capped cordon-bleus, with eight male birds and eight female birds. These birds were randomly paired for multiple two-hour sessions that amounted to more than 200 hours of footage.

With the shots, researchers said that these birds bob up and down and perform their signature dance moves to attract their mate.

When their mate is on the same perch, the cordon-bleu's dancing becomes more rigorous, producing a vibration which scientists say adds a tactile element to the courtship. Their intense dancing produces some kind of non-vocal sound. Scientists said these non-vocal sounds might be a strategy to woo their mate by targeting multiple senses.

"It's a really rare phenomenon that songbirds produce non-vocal sounds," explained Masayo Soma of Hokkaido University in Japan, lead researcher of the study.

Soma said that some species create non-vocal sounds using their wings but these do not commonly use their feet. Birds that do not sing usually perform dances that produce sounds from their tail feathers or wings.

Researchers also found that cordon-bleus execute about six steps at a time which decreases while they are singing. Soma said this happens because the birds try to avoid interference between singing and the non-vocal sounds. It could also be that it is physically exhausting to sing and dance elaborate moves, she said.

Soma said it was not easy to capture the movements of the birds because they were very choosy and only performed displays to the birds that they liked. She and Nao Ota, her student, tried different strategies and eventually got enough footage.

Meanwhile, Soma said they have yet to study what quality in a bird's dancing attracts a mate.

"One possibility is that cordon-bleus are looking for best tap-dance performers, but according to our observation, there was no tendency that [a] particular male or female with more number of steps was popular among the other sex," said Soma, adding that it was a bit puzzling.

Soma said there might be other factors that contribute to mate choice which they will examine in future studies.

Watch the footage here:

Photo: Heather Paul | Flickr