This feather is the outer most primary flight feather on the birds wing, attached to the fused bones of the birds "hand" its basic function is to provide PROPULSION!!!!!
Joe Bob,Thanks for the lesson on bird anatomy. When I saw this feather, I wondered what its function was. Given what you just claimed, do you suspect this bird can't fly anymore given i found this feather on the ground?
It should be noted that the wing of a bird has no tubercules, this is the case with the fins of most fishes and aquatic mammals.
Also, to decrease the ability of a bird to glide you would shorten / pinion this feather on one or both wings.
This bird can still fly fine, granted it is not dead. Birds molt there wings constantly, and if you look close enough on a big boy you can usually see a couple feathers missing just like this one on the wing tips.