According to the IMDB's trivia page for The Shawshank Redemption:
The American Society for the Prevention of Cruelty to Animals monitored the filming of scenes involving Brooks' crow. During the scene where he fed it a maggot, the ASPCA objected on the grounds that it was cruel to the maggot, and required that they use a maggot that had died from natural causes. One was found, and the scene was filmed.
Protecting maggots? Oh, come on!