That's amazing! I hadn't heard of Merlin until I read about it in an article from the Observer magazine; an unknown person sometimes leaves us the paper a day or so on -outside, in a bag!
You may well have seen this
I should have it when I hear that bird that sounds like a very dry frog in the trees near by (we do have frogs, but not tree frogs!)
I will!
I wondered if it might be a jay (they are around) but it's a less urgent noise, more like a frog guiro (below) rather than an actual frog, perhaps. On the other hand, birds have a variety of sounds, so it could be a warbler, a jay or something else..