Ostrich is used in a variety of flies with a surprisingly long history of use for something that seems somewhat exotic. It's twisted to form the little butt between the rear body and tag on classic salmon flies for instance. It's also used in a variety of trout patterns as a natural chenille in a similat fashion.
I like to use it for tentacles on certain squid patterns. It's very well suited to this because the barbs do not compact together. There are some pacific northwest patterns that use it as long hackle, in a Spey hackle style.
I'd imagine it could be used to make excellent crab legs if rubber legs weren't so easy to use instead.
I'm not familiar with feathers from various parts of the bird but the ones I've seen sold are those that are like the ones on the ostrich feather dusters, but dyed.