Rainforest Connection | Publications

Have bird distributions shifted along an elevational gradient on a tropical mountain?

September 28, 2017

An upward shift in elevation is one of the most conspicuous species responses to climate change. Nevertheless, downward shifts and, apparently, the absences of response have also been recently reported. Given the growing evidence of multiple responses of species distributions due to climate change and the paucity of studies in the tropics, we evaluated the response of a montane bird community to climate change, without the confounding effects of land-use change.

Species-specific audio detection: a comparison of 3 template based detection algorithms using random forests

April 24, 2017

We developed a web-based cloud-hosted system that allow users to archive, listen, visualize, and annotate recordings. The system also provides tools to convert these annotations into datasets that can be used to train a computer to detect the presence or absence of a species. The algorithm used by the system was selected after comparing the accuracy and efficiency of three variants of a template-based detection.

Soundscape analysis and acoustic monitoring document impacts of natural gas exploration on biodiversity in a tropical forest

November 18, 2016

We used passive acoustic monitoring in a pre-montane forest in Peru to investigate how soundscape composition and richness of acoustic frequencies varied with distance from a natural gas exploratory well. Results demonstrate that acoustic monitoring and soundscape analyses are useful tools for evaluating the impact of development activity on the vocalizing community, and should be implemented as a best practice in monitoring biodiversity and for guiding specific mitigation strategies.

Audio segmentation using Flattened Local Trimmed Range for ecological acoustic space analysis

June 27, 2016

In this paper, we describe a new spectrogram-based approach for extracting individual audio events. Our goal is to develop an algorithm that is not sensitive to noise, does not need any prior training data and works with any type of audio event. To do this, we propose: (1) a spectrogram filtering method, the Flattened Local Trimmed Range (FLTR) method, which models the spectrogram as a mixture of stationary and non-stationary energy processes and mitigates the effect of the stationary processes, and (2) an unsupervised algorithm that uses the filter to detect audio events.

Impacts of small-scale gold mining on birds and anurans near the Tambopata Natural Reserve, Peru

June 27, 2016

Artisanal and small-scale gold mining (ASM) is becoming a significant cause of environmental degradation in tropical ecosystems. In this study, we conducted a rapid assessment on the impact of an ASM gold mine on the vocalizing avian and anuran communities in the buffer zone of the Tambopata National Reserve in Peru.

Improving distribution data of threatened species by combining acoustic monitoring and occupancy modelling

May 25, 2016

The combination of acoustic monitoring to improve species detectability and statistical methods to account for false-negative detections can improve species distribution estimates. Here, we combine a novel automated species-specific identification approach with occupancy models that account for imperfect detectability to provide a more accurate species distribution map of the Elfin Woods Warbler Setophaga angelae, a rare, elusive and threatened bird species.

Real-time bioacoustics monitoring and automated species identification

July 16, 2013

Traditionally, animal species diversity and abundance is assessed using a variety of methods that are generally costly, limited in space and time, and most importantly, they rarely include a permanent record. In this article, we describe the acoustical component of the Automated Remote Biodiversity Monitoring Network (ARBIMON), a novel combination of hardware and software for automating data acquisition, data management, and species identification based on audio recordings.

Variable response of anuran calling activity to daily precipitation and temperature: implications for climate change

April 4, 2013

Long-term monitoring of frog populations is needed to understand the effects of global change. To better understand the relationships between climate variation and calling activity, we monitored an anuran assemblage in a Puerto Rican wetland by sampling the acoustic environment for one minute every 10 minutes, for 41 months.

Calling activity of the common tink frog in secondary forests of the Caribbean
of Costa Rica

March 19, 2012

Calling activity in terrestrial frogs can be used as a measure of habitat suitability for reproduction. We evaluated the calling activity of the common tink frog Diasporus diastema (Eleutherodactylidae) in 12 secondary forest sites that vary in age of recovery, and three old growth sites in the Caribbean of Costa Rica. Calling activity did not vary among the different forest sites, suggesting that secondary forests can provide suitable habitat for D. diastema reproduction.

Recovery of amphibian species richness and composition in a chronosequence of secondary forests, northeastern Costa Rica

December 27, 2011

In some tropical regions, following the abandonment of agriculture and pastures, secondary forests can recover plant species richness and forest structure (e.g. canopy cover, biomass); however, the importance of these secondary forests for fauna is not clear. We evaluated amphibian recovery in secondary forests in northeastern Costa Rica, by assessing amphibian recovery in 12 secondary forests that vary in age of recovery and in three old growth forests using visual and acoustic surveys.