I spent a decent part of a morning watching this American White Ibis (Eudocimus albus) preen. While the feathers from the neck down looked well-cared for, the ones above appeared a little disheveled. Clearly, there are a few disadvantages to having such an extended mandible!
I read a study from Florida that determined an adult ibis spends well over half the day roosting during nesting season. The birds occupied a good portion of that time with their personal hygiene.
I was surprised to learn that, though they nest in large colonies, they do not practice allopreening (except during courtship). I had presumed they would help each other reach their inaccessible areas but apparently, they just go around half-bathed.