Tap dancers in the wild: field observations of multimodal courtship displays in socially monogamous songbirds

Abstract

Multimodal signaling systems are shaped not only by a signaler's physical abilities but also by external factors such as the position of signal receivers and the properties of the medium through which the signals are transmitted. To fully understand the evolution and function of multimodal communication, it is essential to investigate the behavior in the wild. Here, I present evidence that socially monogamous songbirds perform complex courtship displays that can produce multimodal and multicomponent signals in wild conditions. Cordon-bleus (Uraeginthus spp.) are socially monogamous songbirds from East Africa. Both sexes of cordon-bleus perform multimodal courtship displays by holding a piece of nest material, bobbing up and down, and singing. My previous laboratory study using high-speed video cameras revealed that courtship bobbing includes multiple rapid steps similar to human tap-dancing, which presumably contributes to producing non-vocal sounds and/or vibrations in addition to visual signals. As a result of field observation and behavioral analysis, I found that wild cordon-bleus perform tap-dance like displays just as captive cordon-bleus. I also observed that wild cordon-bleus produced non-vocal sounds and shook branches during courtship, which can contribute to multimodal signal production (i.e., visual, acoustic, and vibrational signals). My findings imply that the courtship displays of cordon-bleus are an ideal candidate for investigating the role and function of multimodal communication in animals, and demonstrate the importance of further quantitative studies in both laboratory and field.

Nesting strategy and the niche partitioning in two socially monogamous songbirds

“…Furthermore, understanding the nesting strategies of wild Estrildids may also give us a hint to elucidate the evolution of their courtship behavior, in which laboratory experiments have accumulated copious amounts of information. Some Estrildid finches including cordon-bleus are known to hold a piece of nest materials in the beak as a courtship component during song and dance (Ota et al 2015, Ota 2020, which is presumably derived from nest-building behavior (Soma 2018). It remains unclear how and why they choose the nest materials during courtship, especially from the viewpoint of ecological plausibility.…”

“…I conducted field observations in Mbeya and Iringa region, Tanzania, during the rainy season from March to May 2019, when cordon-bleus usually start pairing and breeding (Goodwin 1982). The recording of the nests was performed while conducting the field observation of courtship display in cordon-bleus (Ota 2020).…”

“…2). The primary purpose of the expedition was to observe the multimodal courtship display of wild cordon-bleus (Ota 2020), but I could also observe nest-building behavior and the nests during the study (Fig. 2, Movie S1).…”

“…2, Movie S1). When attempting to observe the courtship behavior of cordon-bleus, I usually focus on individuals holding a piece of nest materials on their beak since cordon-bleus perform courtship displays with holding them (Ota 2020). Cordon-bleus holding a piece of nest materials often carried them to their nests (Movie S1) rather than using them for courtship.…”

Non‐visual cues and indirect strategies that enable discrimination of asymmetric mates

“…In fishes, male mottled sculpin ( Cottus bairdi ) produces ‘knock’ sounds by banging their head, the frequency of which in other species indicates male size and serves as a cue for mate choice (Whang & Janssen, 2004 ). The songbird blue‐capped cordon‐bleu ( Uraeginthus cyanocephalus ) performs complex courtship displays that can produce multimodal and multicomponent signals, including a tap dance‐like display wherein they rapidly stamp their feet several times to produce vibrations through the bird's perch (Ota, 2020 ).…”