Hi Simon. As a first approximation, I think it'd be fair to say that, while the behavior is learned, the desire to perform it isn't. Thus, instinctive behaviors are learned in response to unlearned instinctive desires.

It's possible, though, that if we could a microscope to the neural underpinnings of the desire, we'd find that things aren't quite that tidy. The initial desire could be quite vague and inchoate, and could itself be honed as the behavior starts to develop. In other words, the desire and the behavior may develop in concert with one another.

Logically, though, there must be some unlearned starting point, or the whole process could never get off the ground.