Since putting up the log, I witnessed the thrush making two failed attempts at nabbing a grape from it. Back to the drawing board. Meanwhile, I thought I'd vacate the area and see if, left alone, the bird can come up with a workable grape-plucking system. The problem probably lies in removing them from the toothpicks. But if I just hang clusters it's so hard to keep track of usage. And a partially eaten cluster could fall into the water below.
It doesn't look to me like the Costa's Hummingbird is making much progress in growing a gorgeous gorget. By the looks of all those white pin feathers he's still got a ways to go.