人类发出的噪音——从交通的喧闹声到重机械的咆哮声——对于鸟类是有害的，是因为在高噪音地区发现的鸟类已经越来越少了，这已经不是什么秘密了。
然而有一些物种，特别是那些吟唱低调歌曲的大型鸟类，如西部唐纳雀，却特别容易受到人造噪音的折磨。
美国博尔德市科罗拉多大学的动物学家Clinton D. Francis和同事日前在《科学公共图书馆—综合》上报告了这一研究成果。
研究人员计算了位于美国新墨西哥州北部响尾蛇峡谷野生动植物保护区内的鸟类和鸟巢数量，这一地区毗邻着数以千计的天然气井，其中大多数都安装了不停咆哮的压缩机——想一想聆听15米开外的摩托车的感觉。
在对从黑颌蜂鸟到北美哀鸠的30余种鸟类进行调查后，研究人员发现，更大型的鸟类——例如北美哀鸠和西部唐纳雀——会远离这些噪音。
研究人员表示，这些大型鸟类可能是被迫离开这些吵闹的地区的，这是因为喧闹的机械淹没了它们低沉的叫声，从而使得鸟类很难听到彼此的叫声。
而体型较小的鸟类——例如褐斑翅雀鹀——则会唱出一些高调的歌曲，这些物种似乎没有受到影响，这或许是因为它们的叫声依然能够盖过机械的轰鸣。
研究人员指出，从物理学的角度来看，噪声是发声体做无规则振动时发出的声音。从环境保护的角度看，凡是妨碍到人们正常休息、学习和工作的声音，以及对人们要听的声音产生干扰的声音，都属于噪声。作为一种引起人烦躁、或因音量过强而危害人体健康的声音，噪声对动物的危害同样不容小觑。（生物谷 Bioon.com）
doi:10.1371/journal.pone.0027052
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Noise Pollution Filters Bird Communities Based on Vocal Frequency
Clinton D. Francis, Catherine P. Ortega, Alexander Cruz
Background Human-generated noise pollution now permeates natural habitats worldwide, presenting evolutionarily novel acoustic conditions unprecedented to most landscapes. These acoustics not only harm humans, but threaten wildlife, and especially birds, via changes to species densities, foraging behavior, reproductive success, and predator-prey interactions. Explanations for negative effects of noise on birds include disruption of acoustic communication through energetic masking, potentially forcing species that rely upon acoustic communication to abandon otherwise suitable areas. However, this hypothesis has not been adequately tested because confounding stimuli often co-vary with noise and are difficult to separate from noise exposure. Methodology/Principal Findings Using a natural experiment that controls for confounding stimuli, we evaluate whether species vocal features or urban-tolerance classifications explain their responses to noise measured through habitat use. Two data sets representing nesting and abundance responses reveal that noise filters bird communities nonrandomly. Signal duration and urban tolerance failed to explain species-specific responses, but birds with low-frequency signals that are more susceptible to masking from noise avoided noisy areas and birds with higher frequency vocalizations remained. Signal frequency was also negatively correlated with body mass, suggesting that larger birds may be more sensitive to noise due to the link between body size and vocal frequency. Conclusions/Significance Our findings suggest that acoustic masking by noise may be a strong selective force shaping the ecology of birds worldwide. Larger birds with lower frequency signals may be excluded from noisy areas, whereas smaller species persist via transmission of higher frequency signals. We discuss our findings as they relate to interspecific relationships among body size, vocal amplitude and frequency and suggest that they are immediately relevant to the global problem of increases in noise by providing critical insight as to which species traits influence tolerance of these novel acoustics.
