Abstract
Many animal signals are complex, often combining multimodal components with dynamic motion. To understand the function and evolution of these displays, it is vital to appreciate their spatiotemporal organization. Male broad-tailed hummingbirds (Selasphorus platycercus) perform dramatic U-shaped courtship dives over females, appearing to combine rapid movement and dive-specific mechanical noises with visual signals from their iridescent gorgets. To understand how motion, sound and color interact in these spectacular displays, we obtained video and audio recordings of dives performed by wild hummingbirds. We then applied a multi-angle imaging technique to estimate how a female would perceive the male’s iridescent gorget throughout the dive. We show that the key physical, acoustic and visual aspects of the dive are remarkably synchronized—all occurring within 300 milliseconds. Our results highlight the critical importance of accounting for motion and orientation when investigating animal displays: speed and trajectory affect how multisensory signals are produced and perceived.
Highlights
Many animal signals are complex, often combining multimodal components with dynamic motion
Multimodal signals are common in courtship behaviors[11,17,18,19,20] and can have diverse functions[13,21] related to their informational, aesthetic, and sensory content[22]
Work on multimodal signals is proliferating[12,14], we still know relatively little about the temporal organization of complex displays—and the extent to which signal components are synchronized[2,11]
Summary
Many animal signals are complex, often combining multimodal components with dynamic motion. A new framework for analyzing complex signals—rooted in systems theory—has recently been proposed[12,14] This framework emphasizes the importance of understanding the relationship between structure and function in signal design, in the context of signals that are multimodal (involving more than one sensory modality) and dynamic (variable in time and space). Work on multimodal signals is proliferating[12,14], we still know relatively little about the temporal organization of complex displays—and the extent to which signal components are synchronized[2,11] It is becoming increasingly clear, that the timing and ordering of signal components can have large impacts on signal function and perception. Broad-tailed hummingbird courtship dives appear to be complex[12,14], including multiple components and multiple modalities (acoustic, visual). The degree to which different components of the male’s dive display are synchronized is unknown
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