Lianas Abundance is Positively Related with the Avian Acoustic Community in Tropical Dry Forests

Hilje, Branko; Stack, Shauna; Sánchez‐Azofeifa, Arturo

doi:10.3390/f8090311

Cited by 16 publications

(3 citation statements)

References 44 publications

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“…It measures the disparity between the quietest and loudest 1 kHz frequency bins. Again, the BI has been found to be a good predictor of diversity in some studies (Eldridge et al., 2018; Gasc et al, 2017; Hilje et al, 2017; Mitchell et al, 2020) while others have found it to be poor (Fuller et al., 2015; Moreno‐Gómez et al, 2019), although concerns about the limitations of the methodologies used in these studies apply here too. We expect both indices to increase with increasing species richness and species abundance, and for correlations between both abundance and richness with the indices to be strongest in the frequency and time bins that are most dominated by the target taxa (Table 2), particularly diurnal bird species at dawn between 0.3 and 12 kHz and nocturnal taxa at night between 0.3 and 4 kHz.…”

Section: Methodsmentioning

confidence: 78%

Acoustic indices perform better when applied at ecologically meaningful time and frequency scales

et al. 2020

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Acoustic indices are increasingly employed in the analysis of soundscapes to ascertain biodiversity value. However, conflicting results and lack of consensus on best practices for their usage has hindered their application in conservation and land‐use management contexts. Here we propose that the sensitivity of acoustic indices to ecological change and fidelity of acoustic indices to ecological communities are negatively impacted by signal masking. Signal masking can occur when acoustic responses of taxa sensitive to the effect of interest are masked by less‐sensitive acoustic groups, or target taxa sonification is masked by non‐target noise. We argue that by calculating acoustic indices at ecologically appropriate time and frequency bins, masking effects can be reduced and the efficacy of indices increased. We test this on a large acoustic dataset collected in Eastern Amazonia spanning a disturbance gradient of undisturbed, logged, burned, logged‐and‐burned and secondary forests. We calculated values for two acoustic indices: the Acoustic Complexity Index and the Bioacoustic Index, across the entire frequency spectrum (0–22.1 kHz), and four narrower subsets of the frequency spectrum; at dawn, day, dusk and night. We show that signal masking has a large impact on the sensitivity of acoustic indices to forest disturbance classes. Calculating acoustic indices at a range of narrower time–frequency bins substantially increases the classification accuracy of forest classes by random forest models. Furthermore, signal masking led to misleading correlations, including spurious inverse correlations, between biodiversity indicator metrics and acoustic index values compared to correlations derived from manual sampling of the audio data. Consequently, we recommend that acoustic indices are calculated either at a range of time and frequency bins, or at a single narrow bin, predetermined by a priori ecological understanding of the soundscape.

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Section: Methodsmentioning

confidence: 78%

Acoustic indices perform better when applied at ecologically meaningful time and frequency scales

et al. 2020

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“…Moreover, ACIt f has been used to investigate animal phenology [89,90] and to estimate the effect of anthropogenic noise [91]. This index has also been demonstrated to be a good proxy of richness and diversity of the communities in forest areas [74,92] and marine and freshwater systems [93][94][95]. The graphic representation of ACIt f depicts the acoustic signature.…”

Section: Characteristics Of Acit F and Acif Tmentioning

confidence: 99%

Ecoacoustics: A Quantitative Approach to Investigate the Ecological Role of Environmental Sounds

Farina

2018

Mathematics

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Ecoacoustics is a recent ecological discipline focusing on the ecological role of sounds. Sounds from the geophysical, biological, and anthropic environment represent important cues used by animals to navigate, communicate, and transform unknown environments in well-known habitats. Sounds are utilized to evaluate relevant ecological parameters adopted as proxies for biodiversity, environmental health, and human wellbeing assessment due to the availability of autonomous audio recorders and of quantitative metrics. Ecoacoustics is an important ecological tool to establish an innovative biosemiotic narrative to ensure a strategic connection between nature and humanity, to help in-situ field and remote-sensing surveys, and to develop long-term monitoring programs. Acoustic entropy, acoustic richness, acoustic dissimilarity index, acoustic complexity indices (ACItf and ACIft and their evenness), normalized difference soundscape index, ecoacoustic event detection and identification routine, and their fractal structure are some of the most popular indices successfully applied in ecoacoustics. Ecoacoustics offers great opportunities to investigate ecological complexity across a full range of operational scales (from individual species to landscapes), but requires an implementation of its foundations and of quantitative metrics to ameliorate its competency on physical, biological, and anthropic sonic contexts.

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“…Lianas provide perching, lekking, and breeding sites, as well as nest materials and nesting sites for many bird species (Michel et al 2015 b ). Indeed, in an observational study in a dry forest in the Guanacaste province of Costa Rica, Hilje et al (2017) found that bird community diversity increased with increasing liana density.…”

Section: Introductionmentioning

confidence: 99%

Lianas maintain insectivorous bird abundance and diversity in a neotropical forest

Schnitzer

Michel

Powers

et al. 2020

Ecology

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The spatial habitat heterogeneity hypothesis posits that habitat complexity increases the abundance and diversity of species. In tropical forests, lianas add substantial habitat heterogeneity and complexity throughout the vertical forest profile, which may maintain animal abundance and diversity. The effects of lianas on tropical animal communities, however, remain poorly understood. We propose that lianas have a positive effect on animals by enhancing habitat complexity. Lianas may have a particularly strong influence on the forest bird community, providing nesting substrate, protection from predators, and nutrition (food). Understory insectivorous birds, which forage for insects that specialize on lianas, may particularly benefit. Alternatively, it is possible that lianas have a negative effect on forest birds by increasing predator abundances and providing arboreal predators with travel routes with easy access to bird nests. We tested the spatial habitat heterogeneity hypothesis on bird abundance and diversity by removing lianas, thus reducing forest complexity, using a large-scale experimental approach in a lowland tropical forest in the Republic of Panama. We found that removing lianas decreased total bird abundance by 78.4% and diversity by 77.4% after 8 months, and by 40.0% and 51.7%, respectively, after 20 months. Insectivorous bird abundance and diversity 8 months after liana removal were 91.8% and 89.5% lower, respectively, indicating that lianas positively influence insectivorous birds. The effects of liana removal persisted longer for insectivorous birds than other birds, with 77.3% lower abundance and 76.2% lower diversity after 20 months. Liana removal also altered bird community composition, creating two distinct communities in the control and removal plots, with disproportionate effects on insectivores. Our findings demonstrate that lianas have a strong positive influence on the bird community, particularly for insectivorous birds in the forest understory. Lianas may maintain bird abundance and diversity by increasing habitat complexity, habitat heterogeneity, and resource availability.

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Lianas Abundance is Positively Related with the Avian Acoustic Community in Tropical Dry Forests

Cited by 16 publications

References 44 publications

Acoustic indices perform better when applied at ecologically meaningful time and frequency scales

Acoustic indices perform better when applied at ecologically meaningful time and frequency scales

Ecoacoustics: A Quantitative Approach to Investigate the Ecological Role of Environmental Sounds

Lianas maintain insectivorous bird abundance and diversity in a neotropical forest

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