I want to know what the nytekrie favorite food??

In my own personal canon, Nyktekries enjoy fish.
This is probably because they are a lot like eagles, at least in my mind. Their beaks also appear to be well suited for eating fish and other meats. They probably catch them with their back feet, sort of like the osprey.
In my canon they also have very good eyesight, like birds of prey, and certain sub-species are nocturnal.
I also think they are large enough for a light human to ride. They are great at gliding and navigating air currents, and are significantly faster flyers than Griffis.
I think they probably nest in tall pine trees or high mountain peaks, namely the latter, so they can glide down and away if startled.
Also, they aren't nearly as vain about the condition of their feathers as Griffi are, and when frightened, a Nyktekrie will stand on its rear legs and beat its wing, whilst screeching.
Nyktekrie do not make good beasts of burden, unless in the air and their load is light.

In a roleplay, one of my Nyktekries, Solntse, enjoys trout above all other types of fish. He hates sea fishing because the spray gets salt in his eyes and blurs his vision.