One problem, I think writers often overlook, is the problem of flying creatures communicating with each other. I call this the "I can't hear you over the sound of the f@cking headwind!"
For my world, this problem is present in three different species:
- Tengu, a race of humanoids with many bird-like features, including wings and beaks.
- Gryphons, hexapodal creatures with the head of an eagle or a corvid and the body of a large feline (usually either a lion, a tiger a cheetah or a lion-sized cheetah).
- Dragons, the six-limbed variant. They aren't that big, but definietly larger than a horse, though they're lighter and not much stronger (except for, ya know, the wings).
All three species have human levels of intelligence and possess airsacs, to help them cope with higher altitudes and make them lighter. Flight speed is around 16-20 m/s for them while gliding.
Now, they do speak the same language, but that isn't the only barrier between them. How can they successfully communicate while flying in an Earth-like atmosphere?