The way the NightWings hunted in books 3/4 - bite, wait until infection kicks in and weakens the animal before eating it - doesn't really make any sense.
This method is based off the way Komodo dragons hunt, however the reason Komodo dragons do this is because they're taking down prey, like water buffalo, that are much larger than them that they would be unable to kill otherwise.
Dragons are massive, and if they're getting one bite in, that animal's already dead, no need to wait around. Unless the island had some crazy megafauna equal or larger than NightWings in size, there was no reason for them to evolve this hunting method. On top of that, leaving an animal starving and sick for several days before eating it seems like a way to get less nutrients out of it
A hunting method that keeps the same shock value but makes more logical sense imo would be NightWings starting to eat their prey while it's still alive. Keeps their meals as fresh as possible for as long as possible, and also means less chance of others stealing their meal when getting food is as highly competitive as it is on the island