Yes, but Ducks soar about as well as a rock though. Have you ever tried landing on the back of a Condor? I'm not saying it can't be done but hey.
I'm not a ornithologist for sure but a mallard isn't a bird of prey, being that high up would suggest it's migrating. If it couldn't glide or soar I doubt it'll make it across even the Thames much less across a continent lol.
Forget a condor even a mallard flies higher think Rüppell's vulture lol.