Sounds like two pebbles being knocked together

Stonechat, so cute, photogenic and an iconic species of upland heath I just couldn't resist uploading another image, this time of a female - look elsewhere on this blog for the male and an immature bird. Mynydd y garn fawr with its drained reservoir supporting cotton grass and spoil tips in the background illustrates the stonechats typical habitat. Note not a dirt bike in sight!