It is the end of the second week of Springwatch and the team looks back at another hectic week on the Sherborne Park Estate, with Chris and Michaela joined by guests Iolo Williams and Lucy Cooke. Gillian Burke investigates Oddball, a piece of mining machinery that was once the largest machine in the world - but since being mothballed has been colonized by all kinds of birds to become what could be the largest bird box in the world.