High-speed cameras reveal that certain songbirds tap dance and sing so speedily that the fancy footwork is otherwise invisible to humans and other animals.

The discovery, published in the journal Scientific Reports, demonstrates how songbirds can flirt, woo, and otherwise communicate with each other completely under the radar of other animals' sensory perceptions.

"The tap dancing is very fast and is completely invisible to the naked human eye," Associate Professor Masayo Soma of Hokkaido University said.

"Even a normal digital video camera cannot capture their motion, as the tapping is quicker than one frame."

Dr Soma, Ms Nao Ota and Professor Manfred Gahr observed the behaviour in the songbirds known as the blue-capped cordon-bleu and the red-cheeked cordon-bleu (from the genus Uraeginthus). They suspect that the blue-breasted cordonbleu, the purple grenadier, the common grenadier and possibly other songbirds also dance and sing in a similar manner.

What's more, the researchers noted that the tap dancing birds would often rhythmically wave around a twig or other eye-catching object as they performed.

The scientists suspect the routines are intricate courtship displays designed to unite a male and female.

"We predict that fine coordination or synchronisation of dancing should relate to long-term pair bonding," Dr Soma said.

The routines even provide intriguing clues about the evolution of dancing in birds, as well as in humans and other animals.

As Dr Soma pointed out, loud singing can "be an advertisement" to anyone within earshot who can detect those particular sounds.

Dancing, on the other hand, is usually much more intimate. While humans may dance on a stage for large audiences, the behaviour is usually reserved in the animal kingdom for visual and even sensual communications meant for a potential mate.

Both male and female songbirds dance

A male red-cheeked cordon-bleu is performing courtship dance ( Nao Ota )

In addition to the novel finding about super speedy tap dancing birds, the study documents the first-known female songbirds that can perform complex courtship displays with the same skill as their male counterparts.

Both male and female cordon-bleu songbirds are extremely choosy, so the scientists suspect that could have contributed to their evolving such elaborate song and dance routines.

Dr Sue Anne Zollinger, a research scientist at the Max Planck Institute for Ornithology, said that although the songbird dancing is invisible to human eyes without special equipment, the birds have higher visual sensitivity, which she referred to as a "higher flicker fusion threshold".

So birds both see and hear the tap dancing moves.

"The complex high speed foot tapping not only adds a visual component to the courtship display, but also an acrobatic element that may demonstrate how physically fit the dancer is," Dr Zollinger said.

"In addition, the foot taps may also add to the acoustic part of the display, like a one-man band that sings while simultaneously playing the drums."

She was very interested to learn of the female dancing and singing skill, since that finding adds to the growing body of evidence that female birds might be more vocal and visually demonstrative than once believed.

In some other bird species, however, it appears that females lost such abilities over evolutionary time.

Dr Zollinger wonders if feeling vibrations created by the foot tapping is an important element of the dancing, given that the birds tend to bust a move in unison when they are next to each other on a perch.

This story was originally published on Discovery.com