I was out on kinder (well, the boggy bit between Rushup Edge and Jacobs Ladder, so NOT Kinder) yesterday and came across a solitary crow sat on a fence post. It was making a noise I'd never heard before - sort of like water tinkling from a metal can. I knew they were great mimics, but I'd never heard something so..unbirdlike coming from a big black bird. Both beautiful and ethereal.
PS. Good job it wasn't around when Mrs T went in the black goo up to her thigh, or it would have learned a whole other set of noises
In reply to toad: There's many a time I've heard a weird call, grabbed the binoculars and gone looking for the 'exotic' bird making the call to find a solitary crow.
Took me six months to pin the local 'mountain-duck quack' down to the same creatures! - They are very shy birds where I live.
Never heard a rook mimicking, but they are very smart birds. I remember in the late 90s/early 00s all the starlings around my way were singing "nokia". Now they just do car alarms