If you are planning to visit residents that are not your family members, you will probably need (as required by many facilities) insurance. Even if you don't need it, you might want it. Imagine getting sued because your bird pecked someone' grandma in the eye.
Insurance is available through just about every therapy animal organization. You'll need to research to see which ones will let you register birds and if chickens are excluded.
Pet Partners is an excellent organization that supports its members well with guidance and education. They allow birds to be registered with them. They require the bird wear a leash, harness, and feces containment device during visits. Additionally, the bird must be docile and easily handled. They may have requirements regarding how the bird is housed and what its diet is to prevent the spread of certain pathogens to the people you visit.
Visits from therapy animals can be wonderful for patients and elderly residents but it isn't as simple as bringing an animal to visit. As a handler you'll have a huge responsibility to the physical and emotional well-being of your animal, the patient, and even that patient's family. As a handler you'll need to learn how to conduct safe visits that are respectful of the patients' rights.