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You never know when this will come in handy. The other day a local birder (hardcore patcher!) got dreadful views of a flighty pipit. Luckily it called a few times. https://twitter.com/sconebirding/status/1313373997216796673
Also luckily, the observer had a recorder handy, and even more luckily, some spare batteries. Even with just a recorder (i.e. without a directional mic) the recording was good enough for a conclusive ID.
It was suspected to be an Olive-backed pipit in the field and the recording confirms this. There is some maths you can do in these things to be super sure https://www.google.co.uk/amp/s/avesrares.wordpress.com/2013/09/27/identification-of-olive-backed-and-tree-pipit-by-call/amp/ but even eyeballing the sonogram allows you to make a good case.
The modulation rate is strongly in favour of OBP.
The steeper gradient of the call compared to tree pipit is also indicative.
The peak frequencies consistently being around 8.5 khz also supports OBP. Tree can call over 8 khz but it is not all that frequent.
So - a pockets worth of kit has saved this from being one that got away. It’s now possible to make a very strong case for this bird to the relevant committee.
