I now have some fairly fat-looking blue tits using the feeder outside my kitchen window. The feeder has two short perches, one either side, and two holes for getting at the food. Today both decided to use the same perch - the one that arrived second lost its grip, turned upside down, and fell off! Fortunately it's only a foot or so above the outside window sill and it picked itself up and flew off pretty quickly. No harm done - but I wouldn't describe it as the bird world's cleverest moment!