I too was just watching the young birds being fed, when a grackle swooped down.. I first thought it was just taking the recently placed food from the beak of a young eurasian tree sparrow. But, no, it was after more.. I guess if I raised and killed the animals I eat, I would be more inured to it. However, my mother, who was reared on a farm, could not eat chicken. 
       The only animal outside watching the scene was the resident rabbit.  When I had schnauzers, they were regularly looking for the rabbit's nest to capture the young. I saved some baby rabbits, some opossums, some snakes,  and some birds from them, but not all.
Jane Allen
St. Louis County
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The Audubon Society of Missouri's Wild Bird Discussion Forum
ASM Website: http://mobirds.org/