Pigeon & Dove deterrent. Mk.1

This year we've been feeding a flock of goldfinches, what messy feeders they are, throwing seed around. To catch some of this food we added saucer like fittings to the bottom of the feeders. Unfortunately this provided perches for larger birds to get at food that wasn't theirs, hence the Mk. 1 P & D deterrent. The tray still catches what the finches drop and small birds can land to collect it, anything larger than a sparrow tilts the tray and they slide off.
It seems to work, so the Mk. 2 will be little different