Research press release


Nature Communications

Zoology: Hummingbird courtship components combine in the blink of an eye



今回、Benedict HoganとMary Caswell Stoddardが、野生の雄のフトオハチドリによる48回の急降下の動画と音声を記録し、そこにマルチアングル映像技術を適用して、雌のフトオハチドリが急降下中の雄の喉の虹色の斑点をどのように認識するのかを調べた。その結果、雄の急降下中に雌が認識する音と色が著しく変化することが明らかになった。著者たちは、雌のフトオハチドリが、近づいてくる雄の音の周波数が6.5%増加し、離れていく雄の周波数が4%減少することをドップラー効果によって認識していると推定しており、この変化が急降下の速度と軌跡に直接関連していると結論付けている。また、急降下の幾何学的形状と高速性を合わせて考えると、雄の喉の斑点が雌に見えるのはほんの一瞬(約120ミリ秒)で、雌が認識する色は赤から黒に急速に変化する。


The courtship displays of male broad-tailed hummingbirds consist of highly synchronized bursts of rapid movement, noises and visual signals that occur within 300 milliseconds (the blink of a human eye). The findings are reported in Nature Communications.

Male broad-tailed hummingbirds perform courtship displays to females by climbing vertically to about 30 metres and making sequential U-shaped dives. During these dives, males produce dive-specific mechanical noises with their tails and visual signals from their gorgets (a patch of colour on the throat). However, the degree to which the different components are synchronized during the display is unknown.

Benedict Hogan and Mary Caswell Stoddard created video and audio recordings of 48 dives performed by male broad-tailed hummingbirds in the wild. The authors then applied a multi-angle imaging technique to determine how a female would perceive the male’s iridescent gorget during the dive. They found that during dives, the sound and colour perceived change dramatically. They estimated that the female perceives a 6.5% shift upwards and 4% shift downwards in the frequency of the male’s sound as they approach and depart respectively, owing to the Doppler effect. This change is directly related to the speed and trajectory of the dive, they conclude. In addition, the geometry of the dive - combined with the high speed - suggests that the male’s gorget is only briefly visible to the female (approximately 120 milliseconds), and the perceived colour changes rapidly from red to black.

The authors argue that their findings highlight the importance of accounting for motion and orientation when investigating animal displays.

doi: 10.1038/s41467-018-07562-7

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