Identifying a bird from sonogram of a phone recording

Back in May, I posted about spectrograms. This is a way of recording a bird call (or any sound, for that matter) in a visual way. You can think about it as a pianola roll, only much more detailed.

With a bit of practice, you can actually read a spectrogram and "hear" the bird in your mind. You can even pick what sort of bird it is from the shape of the specrotrogram.

Here's an example for you to guess.

The other day, I was out getting takeaway when I heard a bird call. It's a bird that turns up each year now in Melbourne about this time. It used to be quite a rarity, but as the years get warmer, I'm hearing them nearly very year.

It was not far away from me, and the background sound wasn't too loud, so I was able to get a recording on my phone with a reasonable signal-to-noise ratio. When I got home, I used Cornell University's free Raven Lite 2 software to convert my recording to a sonogram. 

The sonogram

As you can see, the main note - those four black lines near the bottom of the spectrogram - is pretty simple. It's a half-second whistle, repeated every two or so seconds apart. Each whistle descends a little, before rising and then - maybe - falling just a tiny bit at the end. The pitch never gets very high.

Beyond the main note, there's not a lot going on. It's very pure, with only very quiet harmonics, which show up as the faint parallel lines above the main note. There's no buzzing, which would show up as dense dark marks over a large range of frequencies. There's also no trilling, which would show as a wobbly line.

Other individuals sometimes raise the pitch of the whistles as they repeat, but this guy remained pretty constant. It was almost as though he (I think it was a "he") simply repeated the same whistle over and over again.

So what was it?

The bird was an Eastern (or Common) Koel. These are Cuckoos that migrate as far south as Melbourne to parsitise Wattlebirds or Magpie-larks (or so I read). They do parasitise other hosts as well, but in Melbourne, these are the main targets.