Ummmm... you could turn them in for the reward... Different collections are worth different amounts of coin and even some nice items. In Qeynos, the guy you want is standing by himself under a tree in the park area of North Qeynos near the castle proper.
Can't help you if you're in Freeport... don't live there myself...
Are you still on the Isle? If so, there is a woman on the eastern beach that will take your feathers and shells. Otherwise, above information is correct.