Just off the Pembrokeshire coast lie two small islands-Skomer and Skokholm. The inhabitants number many thousands, of which a few are human. The rest include seals, the unique Skomer voles, and above all great colonies of seabirds like guillemots, kittiwakes, and comical-looking puffins. These bird cities are formed when the ocean wanderers of the winter fly in to become the cliff nesters of the summer. Written and narrated by Tony Soper. Adapted from the Royal Society for the Protection of Birds film.