It would be idiotic and mindless to shoot a potato gun at anything living....
Starlings are native to Europe and here in the UK they used to be so common... You'd see vast clouds of them at winter roost sites like smoke in the sky. They are now in massive decline and there are only a few small Flocks in my area.
They were also extremely useful for ridding the soil of wire worms and leatherjackets etc and were valued by a lot of farmers.
But alas, you have loads of them in the states and they are regarded as a pest and rightly so..Non natives are bad news all round. We have your Grey Squirrel and it is just about the biggest threat to native woodlands here..Strips bark and destroys our native trees wholesale!
One thing worth remembering here is ALWAYS hunt and kill humanely no matter how low a regard you have for the species. They arent evil, they are just an animal introduced by man. they have no right to suffer any more than native species ( so lay off with potato guns etc eh!) Not a lecture here just my point of view.
By the way and back to the point... great shot with the arrow there and keep it up...bit by bit you'll get rid of a few..
I wouldn't think it would be any more idiotic that shooting a blunt tipped small game arrow at a squirrel or rabbit. I would imagine it would make a clean kill. A few years ago I put a crossbow bolt on top of an apple in the potato gun and it shot pretty darn well. I wouldn't hunt big game with a tater gun but I think it would be fun to terrorize yard squirrels with.
I bet it would certianly kill them. If a projectile equel or greater to the game animal's weight, of reasonable density, moving over 70 FPS, hits a solid hit(body, head, etc. Not legs, nose, tail, etc) on it, I think it would kill it very fast. For animals of any size. EX- hit a deer in the main body area with a 100 pound lead cannonball moving pretty fast(say 80 FPS) and you will most likely kill it near-instantly. Hit it with a 100 pound stone in the same spot, it will probably die instantly or near instantly. Hit a human with a 50 pound projectile in the main body (middle-upper chest) and they will likely be dead instantly.
I don't actually know that the above methods will work, but I think its pretty obvious. and-
Early humans could kill a small game animal(rabbit, squirrel, bird) with a 4-6 oz rock throwing it by hand, near 80 FPS or so. Clean, effective kills.