Handling missing data
There were a few instances when recorder failure led to missing data,
most notably in the first half of February 2022. Recorder failure was
typically caused by low battery voltage and resulted in premature
termination of recordings, i.e., files with a duration of less than 29
minutes and 55 seconds. A complete record of all dates and times with
missing data can be found in the Supporting Information. When reporting
number of vocalizations per hour or per month, the true recording
duration was used as the denominator to account for missingness in the
time series and variability in the duration of months. Hours with
greater than 60% missingness were omitted from the time series.