Every year, more and more gannets come to Britain to breed, Today there are more than 100,000 of them crammed on to one lump of rock: Bass Rock. Watching them dive into the sea at more than 60 miles an hour leaves Alan Titchmarsh as breathless as the birds themselves. Alan then visits the puffin colony on Skomer Island off the coast of Wales. Puffins are about the size of a pigeon and each one stands guard over its hole which may be eight or nine feet long. At the end of the hole will be a single chick known as a puffling, to which the parent will bring small fish.