What would be anatomy of a massive (magic)antigrav bird?

Question

Imagine a massive bird, size even larger than pterosaur (Quetzalcoatlus), at about 300 kg. It's able to use a magic that allows it to make its bones have negative gravitational mass(but not negative inertial mass) and rest of its body become lighter. When antigravitating, the bird's weight thus goes down to only 5-10%.

However, the bird burns through its magic power at a rate, being able to antigravitate for only two hours without rest and requiring 3 hours of rest/6 hours of land based functioning per an hour of magic flight. What anatomic features would this large bird develop, since it wouldn't have need to generate as much lift?

Answer 1

What anatomic features would this large bird develop, since it wouldn't have need to generate as much lift?

I suspect it would look very much like other very large winged animals, and it would still be weight-optimised and generate a good deal of lift.

This is because magical flight is expensive. Self-powered winged flight is also quite expensive, and so the large flyers alive today spend a lot of their time gliding. The hard bit is getting airborne, but with your magical antigravity trick that will take almost no effort at all. The bird can use its antigravity to gain altitude without the need for strong local thermal currents or for powerful legs just to get clear of the ground. Once up there it can glide around as long as it likes whilst it searches for prey, or mates, or just admires the view. The additional time required to recharge becomes fairly inconsequential because the trick is used so little.