auk beak bird cliff edge feet Fratercula arctica Great Britain natural nature Pembrokeshire puffin Skomer Island united kingdom wales webbed welsh wings animals Balanus barnacles beach coast creature crustacea marine Mollusca mussels Myrtilus rocks sealife blue boundary Devon England field fields hedge hill hillside landscape sky snow snowy uk view winter coastline exercise footpath fun green sea steps track trail travel Trek walk water ancient architecture arrow battlement castle defence defend fortress gatehouse protect protection secure security slot stone turret algae pool rock sand seaweed tide cloud countryside crop farm panorama rural South Downs summer Sussex