Spring’s increasing day length triggers a hormonal change in birds that enlarges the parts of the brain controlling song production. The result is one of Britain’s most accessible wildlife dramas – the dawn chorus. To experience it fully you have to be up before sunrise, and with a little knowledge you can start to break the wall of sound into individual species. Among the earliest birds to sing are large-eyed robins, thrushes and redstarts, followed by smaller insect-eaters such as wrens, dunnocks and warblers. Morning is when females are most receptive to fertilisation after producing an egg and males sing to proclaim their territory and defend their paternity rights.