Every day, at several intervals, I hear a very distinct, unmistakable two-note call. It's relatively low-pitched compared to other birds I hear nearby, and comes out of nowhere - it sounds once, and is then silent for long periods of time. Every time I hear it I rush to the window but can't see where it came from!
It's particularly noticeable because it usually happens when things have quietened down outside in the evening (it's summer now). I can't predict or record it because it always happens just once, all of a sudden. Two notes then nothing for hours. The two notes are almost the same but I think the second one is slightly lower. It's not a chirp, it's more of a whistle. And it's always the same.
There is a hedgerow outside my house, with woods down the lane, as well as fields. I see and hear many different birds, but cannot identify this one for the life of me. There are house martins and starlings in my eaves, and I often see sparrows and wagtails too. I don't think it is them?
It's been bothering me for weeks! Any ideas what it could be?