Last November, the discovery published in Nature by Manfred Gahr, Nao Ota, and Masago Soma unveiled the speedy and unique “tap dancing” of cordon-bleu songbirds as a courtship display. In addition to uncovering this elaborate courtship display they found that, contrary to common belief that female birds have less sophisticated courtship displays than male birds, female cordon-bleu songbirds can perform tap dancing as complex as that of their male counterparts.
These birds’ unique way of attracting mates is performed at such a high speed that human eyes cannot see the astonishing phenomenon without advanced imaging tools. Soma, an associate professor at Hokkaido University, pointed out that even a normal digital video camera cannot capture their motion. By using a high-speed video camera with 300 frames per second, researchers were able to observe the tap dancing and determine that each step lasted about six frames, approximately 0.02 seconds. The tap dancing was at first assumed to produce vibrations and non-vocal sounds to attract other songbirds. As it turns out, although the tap dancing is invisible to unaided human eyes, the songbirds can see each other dancing because they have a much higher visual sensitivity. Sue Anne Zollinger, a researcher at the Max Planck Institute for Ornithology, referred to this heightened visual capacity in an interview with the Discovery Channel as a “higher flicker fusion threshold.”
Gahr and Soma observed this tap dancing behaviour in other closely related songbirds, such as the blue-capped cordon-bleu and the red-cheeked cordon-bleu, both of which are from the genus Uraeginthus. They inferred that three other species in the same genus – the blue-breasted cordon-bleu, the purple grenadier – and the common grenadier, may also tap dance in a similar fashion. Gahr noted in an interview with BBC, “maybe more birds are doing it, but it just has not been seen.”
Zollinger also explained in her interview that “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.” Gahr and Soma also noticed that while the songbirds were tap dancing and singing, they would also wave around a twig. Soma said it is predicted that “fine coordination or synchronization of dancing should relate to long-term pair bonding.” Soma also pointed out these socially monogamous birds are particularly selective when it comes to picking their mates; the songbirds only perform courtship displays to other birds they found attractive.
Additionally, this speedy footwork holds clues about the evolution of dancing in humans and other mammals. Dancing is a more intimate form of courtship for the potential mates, whereas singing is audible to any bird who can hear the sound, like an “advertisement,” as described by Soma. Zollinger has pointed out that the speed dancing not only serves as a visual component to the courtship display, it also suggests how physically fit the dancer is. “[Tap dancing is] quite complicated, to do all that without falling from the perch – it’s very acrobatic,” Gahr added.
Besides the unprecedented observation of tap dancing, the study documents the first known female songbirds whose courtship displays are as complex as their male counterparts’. Classical selection theory suggested that courtship displays evolved in males because females are believed to have the choice to select mates. However, in this study, dance performance varied amongst individual birds, but did not differ within sexes – both males and females escalated their dance when their mate was on the perch. This could suggest an angle for future studies in considering courtship as a two-way sexual communication, potentially focusing on how multimodal courtship display is evolved in both sexes to give us a more diverse and complex understanding of the bird kingdom.