Often I've wondered why the chicks sometimes leave small (relatively speaking) pellets on the low edge at the back of the nestbox. This morning, part of that was revealed ... not peregrines but a pair of pigeons (fat pigeons) perching on that low edge right at the back of the nestbox ... and leaving little "calling cards". Saw them climb down and sit in the sun against the south wall at the back of the nestbox for a few minutes but missed their departure from the box - no evidence of murder or mayhem, so I assume all went well. Will have to check the recorder when I have a bit more time ...