Well spotted. I think you're right. It must have been about 15 years ago, so I can't recall where I found them, most likely by the coast though.Wonderful!
I think your herring gull is not a herring gull, these might be tailfeathers from a curlew (see https://www.featherbase.info/nl/species/Numenius/arquata) or from something else.
Cheers,
Tom
This post became much less confusing when I remembered you don't live in the UK.(as usual sadly no pics...) my collection currently includes a skull of: raccoon, coati, sloth, monkey and crocodile (found an entire 4ft carcass on the beach recently) and an indigenous stone axe and stone adze head each (=found along the river, our area is rich in old burial grounds and pottery shards are common finds in the garden + once a megalodon tooth; nothing worth taking to a museum i hasten to add )