Audio recordings
Audio data was collected continuously for two years at each recording
station for a total of about 70,000 hours. Each audio file begins on the
half hour and has a duration of 29 min 55 sec, with a 5 second rest
period between files for data writing. The study period ran from June
2020 – May 2022. Data was recorded on AudioMoth acoustic recorders
(Open Acoustic Devices) modified for long-term deployment: eight
supplementary battery packs were wired in parallel to each AudioMoth,
increasing the potential battery life eight-fold, and each unit was
placed inside a custom-built waterproof 15x20x10 cm enclosure, with an
aperture for the microphone protected by a waterproof acoustic membrane
and a wire mesh. Units were deployed at shoulder height and attached to
a tree via python lock. Units were checked once every 5 weeks to replace
batteries, SD cards and desiccant, and to collect data. Every 5 weeks,
units were given enough battery power and SD memory to collect data
continuously for another 6 weeks, to provide a one-week buffer.
AudioMoth units were set to collect data with a 16 kHz sampling rate,
medium gain, and no subsampling or filtering. All recording units were
deployed inside forest and at least 50 m from the nearest publicly
accessible trail to minimize human disturbance.