Table 2. Seasonality indices by species. R is a measure of signal strength, or how concentrated vocal activity is within a specific time of year. R=1 when all vocal activity is concentrated into a single month, and R=0 when vocal activity is equally distributed throughout the year. θ is the time of year when vocal activity was at its peak, measured in radians; month names are included in parenthesis for convenience. ROverall is R of the full 2-year time series, and θOverall is θ of the full 2-year time series.