Sound is an important way of communication among organisms. The monitoring and analy-sis of biological sound is an emerging method to describe and evaluate biodiversity. This method does not invade or damage the natural environment. By recording ecological information through sound, it can effectively reflect the relevant characteristics of biodiversity. The sound-based exploration of biodiversity change has broadened the interdisciplinary approach and has been increasingly applied to ecological research. Here, we expounded on the main theoretical foundations and research methods of using acoustic monitoring to assess biodiversity. We introduced related research fields from two aspects, namely the biodiversity of vocal animals and the temporal and spatial diversity of soundscape. We presented examples of the application of acoustic monitoring to assess the impact of land-use change, climate change and urbanization on biodiversity. Finally, we proposed the future direction of development, and hope that the potential of sound surveys could be further explored to provide an effective reference for biodiversity monitoring and assessment.

声音是生物之间交流的重要手段,对生物声音的监测与分析是描述和评估生物多样性的新兴方法。这种方法不侵入和破坏自然环境,通过声音记录生态信息,并有效反映生物多样性的相关特征,是一种重要的生态工具。从声音角度探讨生物多样性的变化拓宽了多学科交叉的新思路,因此近年来被越来越多地应用于生态学研究中。本文阐述了利用声音监测评估生物多样性的主要理论基础和研究方法,从发声动物的生物多样性、声景的时空多样性两个方面介绍了相关领域的研究进展,列举了声音监测在评估土地利用变化、气候变化和城市化对生物多样性影响的应用实例。最后,对未来研究方向进行了展望,希望能进一步挖掘声音调查的发展潜力,为生物多样性的监测评估提供有效的借鉴和参考。

Selective logging in tropical forests changes the local number of animal species (alpha diversity), but it also likely affects species turnover (beta diversity). Whilst such changes are documented in many ecosystems under different disturbances, they are poorly understood in selectively logged tropical forests. By using soundscape recordings across broad spatial scales, we measured soundscape saturation and dissimilarity of pairs of soundscapes, as a proxy of alpha and beta diversity, respectively, in selectively logged and protected tropical forest in Indonesian Borneo. Soundscapes of selectively logged forests were more homogeneous than the soundscapes of never logged forest, and that soundscape saturation of protected forest was higher during the day and lower at night in comparison with selective logging concessions. Synthesis and applications. Selectively logged forests act as an important reservoir of biodiversity. Optimizing such production forests for biodiversity conservation requires the consideration of the total continuous area that is assigned to selective logging, and spatial arrangement of annual cutting blocks, as these could affect beta diversity and its recovery.

There is global concern about tropical forest degradation, in part, because of the associated loss of biodiversity. Communities and indigenous people play a fundamental role in tropical forest management and are often efficient at preventing forest degradation. However, monitoring changes in biodiversity due to degradation, especially at a scale appropriate to local tropical forest management, is plagued by difficulties, including the need for expert training, inconsistencies across observers, and lack of baseline or reference data. We used a new biodiversity remote-sensing technology, the recording of soundscapes, to test whether the acoustic saturation of a tropical forest in Papua New Guinea decreases as land-use intensity by the communities that manage the forest increases. We sampled soundscapes continuously for 24 hours at 34 sites in different land-use zones of 3 communities. Land-use zones where forest cover was fully retained had significantly higher soundscape saturation during peak acoustic activity times (i.e., dawn and dusk chorus) compared with land-use types with fragmented forest cover. We conclude that, in Papua New Guinea, the relatively simple measure of soundscape saturation may provide a cheap, objective, reproducible, and effective tool for monitoring tropical forest deviation from an intact state, particularly if it is used to detect the presence of intact dawn and dusk choruses.© 2017 The Authors. Conservation Biology published by Wiley Periodicals, Inc. on behalf of Society for Conservation Biology.

Monitoring patterns in biodiversity and phenology have become increasingly important given accelerating levels of anthropogenic change. Long-term monitoring programs have reported earlier occurrence of spring activity, reflecting species response to climate change. Although tracking shifts in spring migration represents a valuable approach to monitoring community-level consequences of climate change, robust long-term observations are challenging and costly. Audio recordings and metrics of bioacoustic activity could provide an effective method for monitoring changes in songbird activity and broader biotic interactions. We used 3 years of spring and fall recordings at six sites in Glacier Bay National Park, Alaska, an area experiencing rapid warming and glacial retreat, to examine the utility of bioacoustics to detect changes in songbird phenology. We calculated the Acoustic Complexity Index (ACI), an algorithm representing an index of bird community complexity. Abrupt changes in ACI values from winter to spring corresponded to spring transition, suggesting that ACI may be an effective, albeit coarse metric to detect the arrival of migrating songbirds. The first peak in ACI shifted from April 16 to April 11 from 2012 to 2014. Changes in ACI were less abrupt in the fall due to weather events, suggesting spring recordings are better suited to indicate phenology. To ensure changes in ACI values were detecting real changes in songbird activity, we explored the relationship between ACI and song of three species: varied thrush (Ixoreus naevius), Pacific wren (Troglodytes pacificus), and ruby-crowned kinglet (Regulus calendula). ACI was positively related to counts of all species, but most markedly with song of the varied thrush, the most common species in our recordings and a known indicator of forest ecosystem health. We conclude that acoustic recordings paired with bioacoustic indices may be a useful method of monitoring shifts in songbird communities due to climate change and other sources of anthropogenic disturbance.

Light pollution is considered a threat for bio-diversity given the extent to which it can affect a vast number of behavioral and physiological processes in several species. This comes as no surprise as light is a fundamental, environmental cue through which organisms time their daily and seasonal activities, and alterations in the light environment have been found to affect profoundly the synchronization of the circadian clock, the endogenous mechanism that tracks and predicts variation in the external light/dark cycles. In this context, birds have been one of the most studied animal taxa, but our understanding of the effects of light pollution on the biological rhythms of avian species is mostly limited to behavioral responses. In order to understand which proximate mechanisms may be affected by artificial lights, we need an integrated perspective that focuses on light as a physiological signal, and especially on how photic information is perceived, decoded, and transmitted through the whole body. The aim of this review is to summarize the effects of light pollution on physiological and biochemical mechanisms that underlie changes in birds' behavior, highlighting the current gaps in our knowledge and proposing future research avenues.

Anthropogenic noise changes the acoustic environment in which avian signals have evolved, possibly decreasing active space or the area over which signals may be detected and discriminated by receivers. Linking signal transmission patterns to signal function and species' spatial ecology is important for understanding behavioural changes of receivers in noise. We tested whether varying levels of ambient noise affectstransmission of two structurally distinct sections of male house wren (Troglodytes aedon) song used for short- and long-distance communication. We placed our experiment in an ecological context by measuring signal degradation and attenuation in relation to species-typical spacing patterns to investigate whether song structure is maintained within (short-distance within-pair communication) and between territories (long-distance male-male and extra-pair communication) depending on noise levels. Songs experienced more masking and fell below thresholds for detection and discrimination at shorter distances under noisier conditions. Decay of signal-to-noise ratios and cross-correlation factors in noise were so pronounced that song components used for both short- and long-distance communication did not transmit beyond average territory boundaries. Noise masking could affect species ecology: if signals are not detected by intended receivers in noisier habitats, settlement, space use and social interactions may be fundamentally altered compared to those in quieter environments.

One mainstay of soundscape ecology is to understand acoustic pattern changes, in particular the relative balance between biophony (biotic sounds), geophony (abiotic sounds), and anthropophony (human-related sounds). However, little research has been pursued to automatically track these three components.Here, we introduce a 15-year program that aims at estimating soundscape dynamics in relation to possible land use and climate change. We address the relative prevalence patterns of these components during the first year of recording.Using four recorders, we monitored the soundscape of a large coniferous Alpine forest at the France-Switzerland border. We trained an artificial neural network (ANN) with mel frequency cepstral coefficients to systematically detect the occurrence of silence and sounds coming from birds, mammals, insects (biophony), rain (geophony), wind (geophony), and aircraft (anthropophony).The ANN satisfyingly classified each sound type. The soundscape was dominated by anthropophony (75% of all files), followed by geophony (57%), biophony (43%), and silence (14%). The classification revealed expected phenologies for biophony and geophony and a co-occurrence of biophony and anthropophony. Silence was rare and mostly limited to night time.It was possible to track the main soundscape components in order to empirically estimate their relative prevalence across seasons. This analysis reveals that anthropogenic noise is a major component of the soundscape of protected habitats, which can dramatically impact local animal behavior and ecology.The online version contains supplementary material available at 10.1007/s10980-021-01360-1.© The Author(s), under exclusive licence to Springer Nature B.V. 2022.

Urbanization poses a challenge to bird communication due to signal masking by ambient noise and reflective surfaces that lead to signal degradation. Bird species (especially oscines) have been shown to alter their singing behaviour to increase signal efficiency in highly urbanized environments. However, few studies on the effects of noise on song structure have included birds with low frequency vocal signals which may be especially vulnerable to noise pollution due to significant frequency overlap of their signals with traffic noise. We compared the perch coos of spotted doves (Streptopelia chinensis), a species with very low frequency vocalizations, in different background noise levels across urban and peri-urban areas in Hong Kong. We documented a 10% upward shift in the minimum frequency of coos of spotted doves across the noise gradient (a relatively small but significant shift), and a reduced maximum frequency in urban habitats with a higher density of built up area. Hong Kong doves had significantly higher minimum and maximum frequencies than doves from throughout their range (from mostly rural sites). Our results indicate that urban species with extremely low sound frequencies such as doves can alter their vocalizations in response to variable urban acoustic environments. Copyright © 2016 Elsevier B.V. All rights reserved.

Vocal responses to anthropogenic noise have been documented in several species of songbird. However, only a few studies have investigated whether these adjustments are made in "real time" or are longer-term responses to particular soundscapes. Furthermore, increased ambient noise often is accompanied by structural changes to the habitat, including the introduction of noisy roadways and the removal of native vegetation. To date, no studies have simultaneously investigated the impact of both acoustic and structural disturbance on the same species. The relevance of each of these variables must be quantified if we wish to refine our understanding of the ways in which human activities influence avian communication. In this study, we quantified both among-male and within-male adjustments of song in response to ambient noise, and also investigated whether anthropogenic modifications of the habitat explained variations in songs' parameters. Recordings of songs were collected from male, breeding eastern bluebirds (Sialia sialis) residing in a network of nestboxes distributed across a gradient of anthropogenic disturbance. Levels of ambient noise were associated both with the average song-parameters of each male and with the change in a male's song-parameters between the loudest and quietest periods at his nest box. Males' song parameters were also related to habitat structure, as assessed using geographic information systems techniques. Males in noisier sites produced both higher-pitched and louder songs than did birds in quieter areas. Likewise, individual males demonstrated immediate adjustments to disturbance by noise, increasing the amplitude of their song between periods of quiet and loud ambient noise. Both spectral and temporal aspects of a male's song were related to whether his habitat was more "natural" or "anthropogenic." Our results indicate that males' adjustments of song may represent simultaneous responses to multiple modifications of the habitat by humans. However, we also conclude that biotic noise remains an important influence on avian signals even in anthropogenic areas. We suggest that human habitats provide an ideal setting in which to perform experiments on communication strategies, with resulting data poised to reveal underlying evolutionary processes while also informing conservation and management. © The Author 2015. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

The urban landscape constitutes a key aspect of human - nature interactions, as more than 60% of the world's population resides in cities and their suburbs. This study focuses on the characteristics of the landscape that humans (and other organisms) perceive as sound and the role of a suburban soundscape in defining experience of place. Vegetation plays an important role in shaping soundscapes, both by creating sound and attenuating sound from natural and human sources. An invasive insect pest, the Emerald Ash Borer (Agrilus planipennis), is killing millions of ash trees (genus Fraxinus) throughout North America. As a result, many municipalities are systematically removing Fraxinus trees. The objective of this research was to determine if and how removal of a substantial amount of the urban forest in such a community causes changes in the local soundscape, particularly in the proportion of human-sourced sounds versus sounds associated with nature. We selected Arlington Heights, Illinois, as the study site, where a series of before-and-after sound recordings were gathered as ash trees were removed between 2013 and 2015. Comparison of recordings using the Raven sound analysis program revealed significant differences in some measures of sound attributes tested as tree canopy decreased. We detected more human-produced mechanical sounds (anthrophony) and fewer sounds associated with weather (geophony) in these sites. Changes in sounds associated with animals (biophony) varied seasonally. We conclude that monitoring changes in the proportions of anthrophony, biophony and geophony provides insight into fauna biodiversity and the human experience of a suburban ecosystem.

Natural sounds, and bird song in particular, play a key role in building and maintaining our connection with nature, but widespread declines in bird populations mean that the acoustic properties of natural soundscapes may be changing. Using data-driven reconstructions of soundscapes in lieu of historical recordings, here we quantify changes in soundscape characteristics at more than 200,000 sites across North America and Europe. We integrate citizen science bird monitoring data with recordings of individual species to reveal a pervasive loss of acoustic diversity and intensity of soundscapes across both continents over the past 25 years, driven by changes in species richness and abundance. These results suggest that one of the fundamental pathways through which humans engage with nature is in chronic decline, with potentially widespread implications for human health and well-being.© 2021. The Author(s).

More humans reside in urban areas than at any other time in history. Protected urban green spaces and transportation greenbelts support many species, but diversity in these areas is generally lower than in undeveloped landscapes. Habitat degradation and fragmentation contribute to lowered diversity and urban homogenization, but less is known about the role of anthropogenic noise. Songbirds are especially vulnerable to anthropogenic noise because they rely on acoustic signals for communication. Recent studies suggest that anthropogenic noise reduces the density and reproductive success of some bird species, but that species which vocalize at frequencies above those of anthropogenic noise are more likely to inhabit noisy areas. We hypothesize that anthropogenic noise is contributing to declines in urban diversity by reducing the abundance of select species in noisy areas, and that species with low-frequency songs are those most likely to be affected. To examine this relationship, we calculated the noise-associated change in overall species richness and in abundance for seven common songbird species. After accounting for variance due to vegetative differences, species richness and the abundance of three of seven species were reduced in noisier locations. Acoustic analysis revealed that minimum song frequency was highly predictive of a species' response to noise, with lower minimum song frequencies incurring greater noise-associated reduction in abundance. These results suggest that anthropogenic noise affects some species independently of vegetative conditions, exacerbating the exclusion of some songbird species in otherwise suitable habitat. Minimum song frequency may provide a useful metric to predict how particular species will be affected by noise. In sum, mitigation of noise may enhance habitat suitability for many songbird species, especially for species with songs that include low-frequency elements.© 2012 Blackwell Publishing Ltd.

Aim On islands, species richness is reduced and interspecific competition relaxed in relation to the mainland, allowing species to use broader ecological niches. These factors are known to affect diet and morphology, but can also affect communication and acoustic signalling in particular. However, no study has ever compared insular and continental soundscapes to determine to which extent islands present reduced acoustic richness (number of co-vocalizing species) and fewer constraints for vocalizing species. Location Sao Tome Island, Mount Cameroon, Madeira Island, Southern France. Taxon Birds. Methods We compared two pairs of insular and continental soundscapes: one in a temperate zone, the other in the tropics. We recorded sounds produced in similar types of primary forests and measured acoustic richness and ambient noise profiles. We then assessed acoustic niche organization by computing, for each community, species turnover, temporal and frequency overlaps, and acoustic avoidance. Results We found fewer species co-vocalizing on islands compared to mainland and in temperate compared to tropical region. Ambient noise was louder in the tropics and occupied a wider frequency range, especially on the mainland, thereby revealing a reduction in available acoustic space for tropical mainland birds. In this more crowded and noisy soundscape, species presented a higher acoustic turnover, overlapped less in time and in frequency with each other and acoustically avoided each other more when compared to the three other communities. Main conclusions Soundscapes differed and imposed fewer constraints on vocalizing species along the species diversity gradient from tropical mainland to temperate island. Acoustic niche partitioning increased with species richness and was associated with increased levels of acoustic interference. Results set a scene for an effect of relaxed competition on song evolution on islands, especially in the tropics.

Structural complexity is known to determine habitat quality for insectivorous bats, but how bats respond to habitat complexity in highly modified areas such as urban green spaces has been little explored. Furthermore, it is uncertain whether a recently developed measure of structural complexity is as effective as field-based surveys when applied to urban environments. We assessed whether image-derived structural complexity (MIG) was as/more effective than field-based descriptors in this environment and evaluated the response of insectivorous bats to structural complexity in urban green spaces. Bat activity and species richness were assessed with ultrasonic devices at 180 locations within green spaces in Vienna, Austria. Vegetation complexity was assessed using 17 field-based descriptors and by calculating the mean information gain (MIG) using digital images. Total bat activity and species richness decreased with increasing structural complexity of canopy cover, suggesting maneuverability and echolocation (sensorial) challenges for bat species using the canopy for flight and foraging. The negative response of functional groups to increased complexity was stronger for open-space foragers than for edge-space foragers., a species foraging in open space, showed a negative response to structural complexity, whereas, an edge-space forager, was positively influenced by the number of trees. Our results show that MIG is a useful, time- and cost-effective tool to measure habitat complexity that complemented field-based descriptors. Response of insectivorous bats to structural complexity was group- and species-specific, which highlights the need for manifold management strategies (e.g., increasing or reinstating the extent of ground vegetation cover) to fulfill different species' requirements and to conserve insectivorous bats in urban green spaces.

Ambient noise can cause birds to adjust their songs to avoid masking. Most studies investigate responses to a single noise source (e.g., low-frequency traffic noise, or high-frequency insect noise). Here, we investigated the effects of both anthropogenic and insect noise on vocalizations of four common bird species in Hong Kong. Common Tailorbirds () and Eurasian Tree Sparrows () both sang at a higher frequency in urban areas compared to peri-urban areas. Red-whiskered Bulbuls () in urban areas shifted the only first note of their song upwards. Swinhoe's White-eye () vocalization changes were correlated with noise level, but did not differ between the peri-urban and urban populations. Insect noise caused the Eurasian Tree Sparrow to reduce both maximum, peak frequency, and overall bandwidth of vocalizations. Insect noise also led to a reduction in maximum frequency in Red-whiskered bulbuls. The presence of both urban noise and insect noise affected the sound of the Common Tailorbirds and Eurasian Tree Sparrows; in urban areas, they no longer increased their minimum song frequency when insect sounds were also present. These results highlight the complexity of the soundscape in urban areas. The presence of both high- and low-frequency ambient noise may make it difficult for urban birds to avoid signal masking while still maintaining their fitness in noisy cities.© The Author(s) 2021. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology.

Gonadal steroids, most importantly testosterone (T), are considered to be a major factor in the expression of adult song behavior in temperate-zone songbirds. The action of T within specific brain regions involved in the regulation of song may occur either directly, or through its androgenic or estrogenic metabolites. In the present study, we tested steroid-dependence of great tit dawn song by blocking both known pathways of T action by simultaneous implantation of flutamide, an anti-androgen, and ATD, an aromatase inhibitor. By our knowledge, this is the first study investigating the effects of androgen inhibitors on dawn song in free-living birds. Male great tits were implanted during their mate's egg laying stage, being the time of maximal male song activity at dawn. Treatment with ATD and flutamide significantly increased plasma T levels, probably because feedback mechanisms on T secretion were inhibited. The treatment decreased the likelihood of showing dawn song, which is in line with the hypothesis that sex steroids are involved in the endocrine control of song behavior. In males that did show dawn song, we found no evidence for a treatment effect on song quality. Although the implants were present for the larger part of the breeding season, males were able to maintain control of a territory and mate and to complete their brood cycle as successful as control males.

The growing human population concentrated in urban areas lead to the increase of road traffic and artificial areas, consequently enhancing air pollution and urban heat island effects, among others. These environmental changes affect citizen's health, causing a high number of premature deaths, with considerable social and economic costs. Nature-based solutions are essential to ameliorate those impacts in urban areas. While the mere presence of urban green spaces is pointed as an overarching solution, the relative importance of specific vegetation structure, composition and management to improve the ecosystem services of air purification and climate regulation are overlooked. This avoids the establishment of optimized planning and management procedures for urban green spaces with high spatial resolution and detail. Our aim was to understand the relative contribution of vegetation structure, composition and management for the provision of ecosystem services of air purification and climate regulation in urban green spaces, in particular the case of urban parks. This work was done in a large urban park with different types of vegetation surrounded by urban areas. As indicators of microclimatic effects and of air pollution levels we selected different metrics: lichen diversity and pollutants accumulation in lichens. Among lichen diversity, functional traits related to nutrient and water requirements were used as surrogates of the capacity of vegetation to filter air pollution and to regulate climate, and provide air purification and climate regulation ecosystem services, respectively. This was also obtained with very high spatial resolution which allows detailed spatial planning for optimization of ecosystem services. We found that vegetation type characterized by a more complex structure (trees, shrubs and herbaceous layers) and by the absence of management (pruning, irrigation and fertilization) had a higher capacity to provide the ecosystems services of air purification and climate regulation. By contrast, lawns, which have a less complex structure and are highly managed, were associated to a lower capacity to provide these services. Tree plantations showed an intermediate effect between the other two types of vegetation. Thus, vegetation structure, composition and management are important to optimize green spaces capacity to purify air and regulate climate. Taking this into account green spaces can be managed at high spatial resolutions to optimize these ecosystem services in urban areas and contribute to improve human well-being.Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Soundscape ecology studies the patterns of sounds across a variety of spatial and temporal scales, which reflects coupled natural-human dynamics in a changing landscape. We reviewed peer-reviewed studies on soundscape ecology, and summarized the conceptual framework of soundscape ecology, the methodology used and acoustic indices developed in these studies. Current studies primarily focus on the following aspects: 1) acoustic composition of soundscape; 2) acoustic interactions between soundscape components; 3) temporal patterns and spatial variability in the soundscapes; 4) acoustic indices developed for biodiversity monitoring and their efficacy. For future studies on soundscape ecology and biodiversity conservation, we suggest: 1) establishing systematic acoustic monitoring network and data management platform; 2) developing new methods for data collection and analysis (e.g., recording matrix and machine learning algorithm); and 3) treating soundscape as an important resource in future research and conservation.

声景生态学以景观中的声音为研究对象，探讨其在不同时空维度上的分布和变化模式，从而揭示自然环境、野生动物和人类活动的相互作用关系。通过系统检索声景生态学研究的相关文献，本文回顾了该学科的研究框架、研究方法，总结了目前常用的声学指标，重点归纳了声景生态学的研究内容，包括声景组成和各组分间的相互作用，声景的时空格局，以及声景生态学在生物多样性监测中的应用。目前，声景监测中存在的问题主要包括监测的生态系统类型和物种类群有限、声学指标效力有待提高等。建议未来着重推进建立系统性的声景监测网络和数据管理平台；开发和完善音频数据采集、分析方法和评估指标；并重视声景数据的采集，将声景视作一种资源进行研究和保护。