Bird in flight.
There is a challenge that will keep you going for a lifetime. Just any bird will do to start with, but soon you'll want a better shot...
You'll be wanting an interesting bird.
Filling the frame.
In perfect focus.
Without motion blur,
Doing something interesting (catching prey is usually good)
In beautiful lighting.
Here, for instance is my best gull. This was mostly down to hanging around a smelly outfall pipe at the beach at dawn and dusk, taking hundreds and hundreds of pictures, till I got lucky.
Andrew