Current guidelines for the release of  native free-ranging birds
Jan White, DVM; Alida Morzenti, MS
University of California, Davis

Wildlife rehabilitates and veterinarians spend hours providing veterinary and supportive care to injured, orphaned, or diseased wildlife. In the end a decision must be made regarding the release potential of the animal. The process of release should be thoughtful and include a physical exam, consideration of the natural history of the bird, site selection, physical appearance of the bird, and a review of current environmental or human interaction factors. Following is a checklist of those criteria:
1) Appropriateness of release: site; migratory/native species; is the animal approved for release by state biologists?
2) Recovery from all injuries, diseases, or capture care problems: Is physical therapy needed after the bird is healed?
3) Sufficient waterproofing ability: Nearly all birds should repel water when misted. Survival of sea and fresh water birds depends on it.
4) Disease state: dont introduce new diseases to an area
5) Age and survival skills: Different species are self supporting at different ages. Hacking allows pre-fledging birds to learn hunting outside of a flight cage. Make certain that the bird recognizes its native food sources. Some species such as insect eaters may learn easier when fostered in a colony.
6) Tameness and recognition of both conspecifics and enemies: Imprinting must be avoided; this is best done by raising birds with conspecifics. This is especially critical with raptors. The same for tameness; the less human contact, the better for both the bird as well as people. Do not release natural enemies at the same site at the same time.
7) Acclimation orientation and sociability: Acclimation to the environment prior to release is essential. This is essential for birds such as the indigo bunting since they navigate by stars and must be able to observe the night sky during development. Integration into a flock allows socialization to occur prior to migration.
8) Pre-release examination, physical appearance, and case review: Review each case carefully and perform a complete physical exam and blood count on birds prior to release. Ascertain that the bird appears "normal" survival in the wild depends on looking well even if an animal is actually ill.