The main tool used in the sound based field of ornithology that is bird song analysis is your very own ears. Experts know dozens if not hundreds of different songs and can immediately tell you what bird that song originated from. Peter Grant, a researcher that worked with the Galapagos finches could recognize individual birds by there songs. For those who do not have multiple years to listen to bird songs and attempt to memorize them, know that there are a few other tools out there, but there is no going wrong if you want to attempt to memorize a few here and there.
Spectrograms are a immensely helpful tools when it comes to bird song analysis, with many uses ranging from identification, taxonomy, to comparative analysis between similar species. Such 2-dimensional representations of sound are widely used in ornithology. A simple recording that can be done with any kind of device can be uploaded and be worked with a tool such as Raven Viewer on a computer. Raven Viewer, however, is currently in a rocky stage of support and it seems will until further notice be disbanded by the creators. However there are many alternative ways to obtain and work with spectrograms such as websites like Spectrum Analyzer. Once on the website, one can upload a file into the in-browser tool and instantly have a spectrogram generated for the sound file.
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