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Could be, but they did start visiting the other one after I switched from one side of the deck to other. They are nearly identical with very minor differences. I'm leaning more towards the spoilage on this one. Good thought though, I'll keep an eye out for predators.

Ah, yes, that does kind of "spoil" my theory. Birds have such keen eyesight, though. Maybe there was some tiny little discrepancy between the two. Itty bitty little mold spores or something.