Leaving out birds of paradise, etc., that use them to decorate their nests in a display for courtship, why do rats, etc., collect small, shiny objects and secret them away in their burrows?
The same reason that shiny lowriders are popular.
They look pretty.
Seriously.
With their particular eyeballs, perhaps that’s all they can see?
Cuz the chicks dig it!
Really, if an organism can amass a hoard of really interesting stuff…which a potential mate would appreciate…the organism is rewarded with sex!
Be it a raven with a bit of aluminum foil or a guy with a Ferarri, the impulse is the same.