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Guest post: The fascinating world of bird sonograms.

I can ID a few birds by sight, but real birders do it by sound; ie they ID most birds without seeing them; ie they listen for their calls and songs. Some few take it a step further. I heard about this from top birder Mike Kilburn, and we have the pleasure of finding out more about how he goes about recording and IDing birds in Hong Kong. Take it away, Mike.....

Why publishing your observations matters.

Last Friday, towards the end of my regular route from Ngong Ping down to Shek Mun Kap for the Hong Kong Bird Watching Society’s Night Bird Survey I heard an unfamilar screeching call in the darkness that I could not identify. Suspecting it was one of Hong Kong’s three large owls – Brown Wood Owl, Eurasian Eagle Owl, or Brown Fish Owl - I recorded it on my iPhone in the hope that I would be able to find something similar online once I got home.

There is an outstanding free online resource for bird calls – Xeno Canto – but it is so comprehensive that it can be difficult to find what you’re looking for, and sometimes, given the similarity of calls of some species, it is difficult to be certain if you’ve really found a match just by comparing recordings.

On a casual scroll through my YouTube feed the next day I struck gold. Ten years earlier Owen Chiang – another Hong Kong birder and top class photographer – had shared a video of a Brown Fish Owl on Cheung Chau giving a very similar-sounding call on YouTube. I played them both and they sounded pretty similar. So far so good. Next, I made simple sonograms of both my mystery bird and the Brown Fish Owl from Owen’s video, on the very easy to use SpectrumView sound analyser app, and compared them side by side (pix a and b) respectively. This showed that the calls were in the same frequency range (the vertical axis) and had the same basic shape, providing clear evidence that the calls were a good match, and therefore both birds were the same species, allowing me to add Brown Fish Owl to my Night Bird Survey for that night, and add a little more to our knowledge of Brown Fish Owl distribution in Hong Kong.

Owen's recording on the left, Mike's on the right.

The moral of this story is “be like Owen” – and please publish your observations! You never know when it may be useful to someone else!


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