Department of Behavioural Ecology, Adam Mickiewicz University in Poznań, Poznań, Poland.
PLoS One. 2019 Feb 7;14(2):e0211970. doi: 10.1371/journal.pone.0211970. eCollection 2019.
Birds are commonly used as bio-indicators of the quality of environments and the changes to them. Therefore, ecologists put a lot of effort into the monitoring of their population trends. One of the methods used for bird population monitoring is autonomous sound recording. Current studies provide inconsistent results when the number of detected species by autonomous sound recorders was compared with that delivered by an observer. In our study, observers counted birds using a point-count method at 64 random points in forest and farmland. At the same points, autonomous sound recorders recorded the soundscape four separate times (including counting by observer period) and the species present in the recordings were later identified by observers in the lab. We compared the number of species detected by simultaneous observations and recordings, as well as the number of species detected by recorders during four different surveys. Additionally, we calculated the Sorensen index to compare the species composition during different surveys at the same point. We found that observers detected more species than autonomous sound recorders. However, differences in the number of detected species were habitat dependent-observers detected more species than recorders in farmland, but not in the forest. When the time for recording was doubled, recorders were more effective than observers during a single survey. The average Sorensen index between the four repeated surveys performed by autonomous sound recorders ranged from 0.58 to 0.67, however we did not find significant differences in the number of species detected during different surveys conducted at the same point. Our study showed that 10-minutes sampling from the same point gives various species composition estimates but not species richness estimates between different surveys. Therefore, even when recorders detect less species than observers during the simultaneous surveys, increasing the survey duration of recorders may alter this difference. The use of autonomous sound recording for monitoring bird populations should be promoted, especially in forest habitats, as this technique is easier to standardise, eliminates many errors observed in the traditional point-count approach, enables conducting survey during adverse field conditions and delivers more reliable results for the majority of the species.
鸟类通常被用作环境质量及其变化的生物指标。因此，生态学家投入了大量精力来监测它们的种群趋势。鸟类种群监测的方法之一是自主录音。当前的研究表明，自主录音器检测到的物种数量与观察员提供的数量不一致。在我们的研究中，观察员使用点计数法在森林和农田的 64 个随机点上计数鸟类。在相同的点上，自主录音器在四个不同的时间段内（包括观察员计数时间段）记录了声景，然后观察员在实验室中识别了录音中的物种。我们比较了同时观察和记录检测到的物种数量，以及四个不同调查中录音器检测到的物种数量。此外，我们计算了 Sørensen 指数，以比较同一地点不同调查期间的物种组成。我们发现，观察员检测到的物种比自主录音器多。然而，检测到的物种数量的差异取决于栖息地——观察员在农田中检测到的物种比录音器多，但在森林中则不然。当录音时间加倍时，录音器在单次调查中的效果比观察员好。自主录音器进行的四次重复调查的平均 Sørensen 指数在 0.58 到 0.67 之间，但我们没有发现同一地点不同调查中检测到的物种数量存在显著差异。我们的研究表明，从同一地点进行 10 分钟的采样可以提供不同的物种组成估计值，但不能提供不同调查之间的物种丰富度估计值。因此，即使在同时调查中录音器检测到的物种比观察员少，增加录音器的调查时间也可能改变这种差异。应该推广使用自主录音器来监测鸟类种群，特别是在森林栖息地，因为这种技术更容易标准化，消除了传统点计数方法中观察到的许多错误，可以在恶劣的野外条件下进行调查，并为大多数物种提供更可靠的结果。
