As I normally get up at around 5am, I can track the rise and decline of the dawn chorus. It grows from what seems like a roundel of relief at getting through another cold night in January and February, building through the Spring months and reaching a crescendo in May, when the birds have usually already been up for an hour or more before I rise. Then it dies away until now, in August, the city seems all but bare of birds and the sun rises into a silent sky.