I'm certainly not an expert, but it is amazing how much their mouths will change as they grow. Big yellow-rimmed mouth makes a good target for parents to insert food! I've helped raise several wild songbirds (barn swallows, lesser goldfinch, mockingbird, starling, robin) and they all started out looking like these weird little alien creatures with massive yellow mouths. Doesn't take very long before they start to resemble the adult.
Proper ID is important, though, because different types require different diets. I think the bird in that video is a bit older than the one in question. I would guess starling.