So they find a 115 million-year-old duck, and that somehow fills a gap? We have ducks now, with the same features they found in this fossil. The entire article gave no reason why we should think this bird was any different other than in size from modern birds, and they even call it a "near-modern" bird.
And then there's the little problem of not actually having the bird's head.
Amazing, you read the actual journal article? That's an achievement considering it hasn't shown up on the web yet. *drums fingers impatiently*
'Near modern' means there are differences between avian diagnostic traits between the two. They were not modern birds but had fewer differences in those traits than a number of other transitional fossils.
"And then there's the little problem of not actually having the bird's head.
Why is that a problem? It would have to be very like a bird's head because of the limitations the bird morphology creates. We have many fossils that span the dino to bird transition and none of them have a fish, amphibian or mammal heads so expecting this fossil to have a bird (or very bird like) head seems quite reasonable.