its dificult to know the exact reason a hare is at its fittest in winter,,, but i subscribe to the theroy, that its best feeding in summer and autum is over, so its loosing puppy fat,,, also its pretty much fully grown by winter.. also because of the lack of vegitation to hide in, it has to up its game so to speak, in other words that dumb young hare that might of tried to dodge a dog, through cover now has less opertunity to do this.
and of course if its lucky to have survived being ran a few times,,, well that speaks for its self.
i dont think there at the best in march , robert beca