As a result, we discovered that their visual courtship display includes quite rapid step-dancing during bobbing (see results). Here, we analysed the audio-visual displays of the blue-capped cordon-bleu in detail using high-speed video-camera recordings ( Fig. Notably, the courtship bobbing produces rhythmical sounds ( Supplementary Video S1, Supplementary Fig. During these displays, they hold a piece of nesting material, then bob up and down and sing 15 ( Supplementary Video S1). The blue-capped cordon-bleu ( Uraeginthus cyanocephalus), a socially monogamous songbird, is one of the few species in which both sexes perform courtship displays. Furthermore, why a few songbird species use both song and dance displays as intersexual communication is a puzzling question 14. The evolution and mechanisms of dance duets have received far less attention than have vocal duets. In socially monogamous non-passerine birds, dance duets may serve similar functions as vocal duets do in songbirds 12: contributing to pair formation, pair bonding, or mate guarding 13. Elaborate mutual dance displays between sexes are known to be performed by socially monogamous non-passerine birds, which are non-vocal learners, such as grebes 11. Much research has focussed on male–female directed courtship displays performed by polygynous male birds, while the occurrence of both male–female and female–male directed courtship displays performed by socially monogamous birds has often been overlooked. Thus, by coordinating visual and acoustic displays without interference between display components, polygynous male birds can better convey sexual signals 6, 7, 10. Males of polygynous species (e.g., spiders 3, frogs 4, fishes 5 and birds 6, 7) use multimodal courtship displays to increase the efficacy of signalling 8, 9. The fact that both sexes of this socially monogamous songbird perform such a complex courtship display is a novel finding and suggests that the evolution of multimodal courtship display as an intersexual communication should be considered.Įlaborate courtship displays are assumed to have evolved under strong sexual selection pressure in males 1, 2. The multimodal (acoustic, visual, tactile) and multicomponent (vocal and non-vocal sounds) courtship display observed was a combination of several motor behaviours (singing, bobbing, stepping). Both male and female cordon-bleus intensified their dance performances when their mate was on the same perch. Dance performances did not differ between sexes but varied among individuals. By recording these displays with a high-speed video camera, we discovered that in addition to bobbing, their visual courtship display includes quite rapid step-dancing, which is assumed to produce vibrations and/or presumably non-vocal sounds. In the blue-capped cordon-bleu ( Uraeginthus cyanocephalus), a socially monogamous songbird, both sexes perform courtship displays that are characterised by singing and simultaneous visual displays. While it is well-known that socially monogamous songbird males sing to attract females, we report here the first example of a multimodal dance display that is not a uniquely male trait in these birds. According to classical sexual selection theory, complex multimodal courtship displays have evolved in males through female choice.
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