How to compare the syllable extracted from the audio I need to recognize just one bird. I am trying to compare the syllables extracted from the sound samples. As a result of the spectrogram function, the power spectral density is taken from the sound. They are 2 dimensional values. I like to compare this test signal with a known signal which is another 2 dimensional value. Could you please suggest what would be the best function to use for comparison. Please keep in mind that the syllable of the test bird could be time shifted or they closely match the original bird. I am attaching the sample spectrogram and its syllable extracted here after filtering.. 

Regards
A quick google for "bird voice recognition" yielded

https://peerj.com/articles/488/

which has an abstract describing that the authors refined the results they got using the old-school Mel-frequency cepstral coefficient comparison, as it has been common in (human) speech recognition for decades. I could start explaining what cepstrals and Mel-frequencies are, but there's so much literature out there that you literally just have to click read the first thing that hits you when you google for that. It's a relatively well-researched topic.