Traced my drip sounding non drip

Was alerted by my finally tuned householder ear early yesterday morning,  sounded exactly like a slow drip onto plasterboard (as I’ve had that before) , however it appeared to be in a corner of the house where there are no pipes and it hadn’t rained… anyway couldn’t see anything, checked outside, nothing.   Same noise again this morning , but quicker, nothing inside, nothing outside, totally baffled, then, with the low sun I got lucky , on next doors wall was the shadow of a small bird on my tiled roof, gathering nest materials, every peck coinciding with a drip sound …..   problem solved.