'In real life, goshawks resemble sparrowhawks the way leopards resemble housecats. Bigger, yes. But bulkier, bloodier, deadlier, scarier, and much, much harder to see. Birds of deep woodland, not gardens, they're the birdwatchers' dark grail.' As a child Helen Macdonald was determined to become a falconer. She learned the arcane terminology and read all the classic books, including T.H. White's tortured masterpiece, 'The Goshawk', which describes...