BRITAIN'S SMALLEST OWL leaves a big impression. It acts the rude boy at dawn and dusk, rising from its perch to cast a stare of searing ferocity that would almost terrify were the bird not the size and shape of a honeydew melon. There is nothing to fear and much to enjoy about the little owl. Nature lovers register its presence at time-honoured roosts and perches, and watch it hunting in the open, quartering low at twilight. They are charmed by its vocal repertoire: the 'gooek' call of the male; thehissing, snoring young in early summer. But while we may have taken this scowling gremlin to our hearts, the bird could be said to have no place in our heads.