Lowry Hélène, Lill Alan, Wong Bob B M
School of Biological Sciences, Monash University, Clayton Campus, Victoria 3800, Australia.
Department of Ecology, Environment and Evolution, La Trobe University, Bundoora, Victoria 3083, Australia.
Animals (Basel). 2019 Mar 26;9(3):118. doi: 10.3390/ani9030118.
Urban environments are characteristically noisy and this can pose a challenge for animals that communicate acoustically. Although evidence suggests that some birds can make acoustic adjustments that preclude masking of their signals in high-disturbance environments such as cities, studies to date have tended to focus on acoustic signals important in mate attraction (e.g., songs). Far less attention has been given to the impact of urban noise on other kinds of calls. To redress this, we compared a range of different vocalizations (encompassing alarm calls, begging calls and parent response calls) among urban and rural individuals of a successful Australian 'urban adapter', the Noisy miner, . We found that urban miners had significantly higher minimum sound frequencies for calls with low base-frequencies (<2 kHz); however, calls with base-frequencies 'naturally' above the main frequency range of urban noise (>2 kHz) had the same minimum frequency in urban and rural birds. Dominant frequency and call duration did not differ between urban and rural individuals. Although urban Noisy miners exhibited differences from rural individuals in the minimum frequency of calls, this shift was not large enough to avoid masking from low-frequency, anthropogenic noise. Nevertheless, our findings suggest that the calls of Noisy miners may be naturally well suited to being heard in noisy urban environments by having (a) dominant frequencies higher than low-level, anthropogenic noise and (b) several important call-types with frequencies above the main frequency range associated with urban noise.
城市环境的特点是嘈杂，这对通过声音进行交流的动物来说可能是一个挑战。尽管有证据表明，一些鸟类能够进行声学调整，以避免其信号在诸如城市等高干扰环境中被掩盖，但迄今为止的研究往往集中在对配偶吸引至关重要的声学信号（例如歌声）上。城市噪音对其他类型叫声的影响则很少受到关注。为了纠正这一点，我们比较了一种成功的澳大利亚“城市适应者”——吵闹矿工鸟在城市和农村个体之间的一系列不同叫声（包括警报声、乞食声和亲鸟回应声）。我们发现，城市中的吵闹矿工鸟发出的低频（<2千赫）叫声的最低声音频率显著更高；然而，基频“自然”高于城市噪音主要频率范围（>2千赫）的叫声，在城市和农村鸟类中具有相同的最低频率。城市和农村个体之间的主频和叫声持续时间没有差异。尽管城市中的吵闹矿工鸟在叫声的最低频率上与农村个体存在差异，但这种变化幅度不足以避免被低频人为噪音掩盖。尽管如此，我们的研究结果表明，吵闹矿工鸟的叫声可能天生就很适合在嘈杂的城市环境中被听到，因为（a）主频高于低水平人为噪音，（b）几种重要的叫声类型的频率高于与城市噪音相关的主要频率范围。
