Eurasian Tree Sparrow - "Double Chirp"

Whilst cutting a video from the live stream of the 25th of March, I noticed two other types of chirping of the Sparrow. I thus once again examined the frequencies using audacity. The results, I find, are quite interesting.

The plots below depict the frequencies for what I call the "double chirp" and the "single low tone chirp". The video below will help you understand what I mean. At the beginning while the Sparrow is in the nest you can hear the single low tone chirp and afterwards while it is perched in the hole, you can heat three double chirps.



These single and double chirps can also be seen in the image below.



The plot below depicts the difference the frequencies of a double chirp (green line) and a single low tone chirp (blue line).




The plot below depicts the difference the frequencies of a double chirp (blue line) and the cumulative frequencies of the video above.



The plot below depicts the frequencies obtained by examining a single double chirp (blue line) and three double chirps (green line).


Finally, the plot below depicts the difference between the frequencies obtained from three double chirps (red line), the single low tone chirp (blue line) and the frequencies obtained from other chirps in the past (17.03 and 12.03).