Heretic of The Seventh Circle
OkayI guess it comes down to what you mean by "much magic at all" and what you mean by density. Birds can fly mostly because they have less mass, not because they are significantly less dense than other animals*. So are you suggesting they are magically less dense, or that super materials (magic or otherwise) make the less dense?
Also, a dragon that is 30-40% bigger than a quetzalcoatlus would weigh less than a 15' alligator. That is not my idea of a dragon.
*Note: some birds (puffins & loons) don't have hollow bones and neither do flying mammals. Almost all animals have a density close to water. Flying animals are simply less robust with less massive.