Back around the time I first became involved in "buckskinning" (the mountainman thing), there was a federal sting operation trying to catch buckskinners with "illegal" feathers. In case you are not aware, I am not even talking about just eagle or hawk feathers, but the regular, ordinary feathers you might find on the sidewalk. Yes, almost all of them are "illegal" for you to pick up or possess.
In one of the hobby's magazines I read a quote from a fed that stated that the defense of "I found it on the ground" was no defense at all, because "then people might try to use that excuse if caught with a bag of marijuana". I guess one nonsense "law" bolsters another.
In the course of my life I have found thousands of feathers, yet I have only found one bag of pot on the ground. Since I was pretty sure that the guy standing beside it, putting his wallet back into his pocket, had dropped the bag, I picked it up and handed it back to him. Boy, was he grateful! Anyway....
There is an obvious difference between a "shed" feather and one pulled from a bird's body. I can tell the difference but the feds apparently can not. I can assure you that there is no one who gets more angry than me at senseless destruction of wildlife. However, when I find a feather, or even a dead bird, why is it better to let it rot away than to collect the beautiful feathers and use them? Only because the government thinks it owns that bird, and owns you as well. That is a disgusting myth.