Tray suspended under sunflower seed feeder working on goldfinches' sloppy eating

The goldfinches are so darn messy.  Even though the sunflower seeds are shelled, they seem to be interested in only one bite from each and they toss their rejected portions onto the ground.  So, I now have a clear plastic pot tray thing (nice and big, a few dollars at Ritchie's) hanging under the sunflower seed feeder.  So far so good, it really seems to be catching pretty much everything, and the sparrows come along and happily eat the stuff that falls onto the tray.

Sightings of the rat(s) are much fewer now that the sunflower heads from the mammoths are gone.  The presence of the ground cherries is I'm hoping the only thing keeping them here, plus the shelter they've taken under the kitchen step and in the compost bin.