How to compare the syllable extracted from the audio
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.