Urban junco flight initiation distances correlate with approach velocities of anthropogenic sounds

Urban-dwelling birds face novel visual cues and soundscapes. To thrive in these challenging environments, individuals must correctly identify and calibrate threats posed by humans and their activities. We showed that Dark-Eyed Juncos (Junco hyemalis) residing in an urban habitat responded differently to the sounds that approaching people and objects make. A person approached juncos simultaneously playing the sounds of object types that normally move at different relative velocities: faster (bicycles), intermediate (skateboards and scooters), or slower (people walking). Juncos responded at significantly greater distances and moved further in relation to what sound cues would normally imply about the velocity of approach. Absolute stimulus volume was not a significant predictor of response across object type. The responses occurred without the presence of visual cues, suggesting that an auditory cue alone and without visual confirmation can produce an appropriate response. Overall, this s...

栖息于城市环境的鸟类会面临全新的视觉线索与声景（soundscapes）。为在这类充满挑战的生境中存活繁衍，个体必须正确辨识并研判人类及其活动所构成的威胁。本研究显示，栖息于城市生境的暗眼灯草鹀（Dark-Eyed Junco, Junco hyemalis）对接近的人类与物体发出的声响会产生差异化反应。实验中，当人类接近草鹀时，研究人员同步播放通常以不同相对速度移动的物体的声响：高速（自行车）、中速（滑板与踏板车）以及低速（步行的人类）。相较于声响信号本应暗示的接近速度，草鹀的反应触发距离显著更远，且移动幅度也更大。在不同物体类型组中，刺激源的绝对音量均未对受试个体的反应产生显著预测效力。这类避险反应在无视觉线索辅助的情况下即可触发，表明仅靠听觉信号、无需视觉佐证即可催生恰当的应对行为。总体而言，本研究