Frequency Spectra: Sparrow vs. Great Tit

As promised I fed the audio files of the two displays (dated 2010.03.12 and 2010.03.13) to audacity to compare the frequencies used by the two different species (Eurasian Tree Sparrow and Great Tit). As expected there are clear differences. The figure below (click to enlarge) depicts frequencies and normalised dB levels (to remove the dependency on microphone settings). The images below the plot (colour coded for the two birds: blue = Sparrow, read = Great Tit) are the waveforms.



Also interesting is the comparison between the chirping frequencies during the display and during "nesting" as I call it. Below is a plot comparing these for the Eurasian Tree Sparrow (12.03.2010 = Display; 17.03.2010 = Nesting)



It appears that during the display, the male bird does add colour to its singing by increasing the relative importance of the higher frequencies. Unfortunately, I do not have nesting sounds from the Great Tit, so I cannot perform a direct comparison. I will thus have to look this up to see if I can find any backing.