The idea behind a Skinnerbox is it keeps the subjects performing the action even after they're satiated. So, if you wanted the magpies to keep collecting bottle caps even after they've had enough to eat, it might be helpful.
Based on my childhood memories of feeding birds, I don't expect the birds getting full would be a major concern.
Right? Birds are like my dogs, basically food black holes.
Besides, the amount of bottle caps the magpies in the experiment would be able to find in the wild would be a limiting factor keeping them on their toes.
Based on my childhood memories of feeding birds, I don't expect the birds getting full would be a major concern.