Oilbirds produce echolocation signals beyond their best hearing range and adjust signal design to natural light conditions

Oilbirds are active at night, foraging for fruits using keen olfaction and extremely light-sensitive eyes, and echolocate as they leave and return to their cavernous roosts. We recorded the echolocation behaviour of wild oilbirds using a multi-microphone array as they entered and exited their roosts under different natural light conditions. During echolocation, the birds produced click bursts (CBs) lasting less than 10 ms and consisting of a variable number (2–8) of clicks at 2–3 ms intervals. The CBs have a bandwidth of 7–23 kHz at −6 dB from signal peak frequency. We report on two unique characteristics of this avian echolocation system. First, oilbirds reduce both the energy and number of clicks in their CBs under conditions of clear, moonlit skies, compared with dark, moonless nights. Second, we document a frequency mismatch between the reported best frequency of oilbird hearing (approx. 2 kHz) and the bandwidth of their echolocation CBs. This unusual signal-to-sensory system mismatch probably reflects avian constraints on high-frequency hearing but may still allow oilbirds fine-scale, close-range detail resolution at the upper extreme (approx. 10 kHz) of their presumed hearing range. Alternatively, oilbirds, by an as-yet unknown mechanism, are able to hear frequencies higher than currently appreciated.

搜集汇总

背景与挑战

背景概述

该数据集记录了油鸱在不同自然光条件下（黑暗与月光）的回声定位行为，包括点击爆发（CBs）的持续时间、点击次数和频率带宽（7-23 kHz）。研究发现油鸱在月光下会减少信号能量和点击次数，且其回声定位信号频率范围远高于其最佳听力频率（约2 kHz），揭示了信号与听觉系统之间的不匹配现象。