From this press release on the homepage of the American Bird Conservancy:
Citing the need to prevent lead toxicity hazards to wildlife, the Federal Government's primary wildlife management agency, the U.S. Fish and Wildife Service (FWS) has banned the use of lead ammunition for hunting nuisance birds. The decision was published by FWS as a final rulemaking action in the Federal Register. Depredation orders are issued by FWS to allow the killing of migratory birds such as crows, grackles, and blackbirds which are causing damage to public or private property, pose a health or safety hazard, or are damaging agricultural crops or wildlife. This new regulation will require the use of non-toxic ammunition in the control of these nuisance birds.