Fig. 1
Examples of FD calls from six different species. First, four species for which FD calls were detected in large numbers: the oak titmouse (Baeolophus inornatus), the boreal chickadee (Poecile hudsonicus), the great tit (Parus major), the acacia tit (Melaniparus thruppi). We also add the coal tit (Periparus ater, a species with relatively few FD calls in the Paridae) and the fairy flycatcher (Stenostira scita, the one species with FD calls outside of the Paridae). Spectrograms were obtained using the stft (Short-Time Fourier Transform) function from scipy.signal in python, using a window size of 256 samples (nperseg), an overlap of 128 samples (noverlap), and an FFT length of 256 points. The display uses a power scaling factor of 0.6 for best contrast.
