Ralph Martin/ BIA / Blyth's Reed-Warbler (Acrocephalus dumetorum) calling, Ural, Russia

Heike Odermatt / Northern Gannet (Morus bassanus) with nest material, Helgoland, Germany

Heike Odermatt / Northern Gannet (Morus bassanus), Helgoland, Germany

Heike Odermatt / Northern Gannet (Morus bassanus) displaying, Helgoland, Germany

Heike Odermatt / Lesser Black-backed Gull (Larus fuscus) preening, Helgoland, Germany

Heike Odermatt / Lesser Black-backed Gull (Larus fuscus), Helgoland, Germany

Heike Odermatt / Lesser Black-backed Gull (Larus fuscus), Helgoland, Germany

Heike Odermatt / Grey Seal (Halichoerus grypus) pair playing in surf, Helgoland, Germany

Heike Odermatt / Northern Gannet (Morus bassanus) subadult calling, Helgoland, Germany

Heike Odermatt / Northern Gannet (Morus bassanus) subadult, Helgoland, Germany

Heike Odermatt / Northern Gannet (Morus bassanus) with nest material in its bill, Helgoland, Germany

Heike Odermatt / Northern Gannet (Morus bassanus) with chick on nest, Helgoland, Germany

Paul Hobson / Heligoland trap for catching birds, Spurn Point, Yorkshire, UK

Kerstin Hinze / Northern gannet (Morus bassanus) adult flying, Helgoland, North Sea, Germany

Kerstin Hinze / Northern gannet (Morus bassanus) adult flying with head at an angle, Helgoland, North Sea, Germany

Kerstin Hinze / Northern gannet (Morus bassanus) adult flying, Helgoland, North Sea, Germany

Kerstin Hinze / Northern gannet (Morus bassanus) adult flying carrying kelp for nesting material, Helgoland, North Sea, Germany

Kerstin Hinze / Common / Harbour Seal (Phoca vitulina) on beach, Helgoland, North Sea, Germany

Kerstin Hinze / Northern gannet (Morus bassanus) pair displaying at nesting place, Helgoland, North Sea, Germany

Kerstin Hinze / Common / Harbour Seal (Phoca vitulina) on beach, Helgoland, North Sea, Germany

Kerstin Hinze / Common / Harbour Seal (Phoca vitulina) in surf on beach, Helgoland, North Sea, Germany

Kerstin Hinze / Common / Harbour Seal (Phoca vitulina) in surf on beach, Helgoland, North Sea, Germany

Kerstin Hinze / Common / Harbour Seal (Phoca vitulina) on beach, Helgoland, North Sea, Germany

Kerstin Hinze / Common / Harbour Seal (Phoca vitulina) moving up the beach, Helgoland, North Sea, Germany

Kerstin Hinze / Common / Harbour Seal (Phoca vitulina) resting on beach, Helgoland, North Sea, Germany

Heike Odermatt / Northern Gannet (Morus bassanus) pair exchanging nest material mid-flight, Helgoland, Germany

Kerstin Hinze / Two Grey Seals (Halichoerus grypus) play fighting, Helgoland, North Sea, Germany

Kerstin Hinze / Two Grey Seals (Halichoerus grypus) play fighting, Helgoland, North Sea, Germany

Kerstin Hinze / Two Grey Seals (Halichoerus grypus) play fighting, Helgoland, North Sea, Germany

Kerstin Hinze / Grey Seal (Halichoerus grypus) looking backwards over its shoulder on the beach, Helgoland, North Sea, Germany

Kerstin Hinze / Two Grey Seals (Halichoerus grypus) play fighting, Helgoland, North Sea, Germany

Bernard Castelein / Oystercatcher (Haematopus ostralegus) preening tail, Helgoland, Germany

Bernard Castelein / Grey seal (Halichoerus grypus) covering nose with flipper, Helgoland, Germany

Bernard Castelein / Oystercatcher (Haematopus ostralegus) preening, Helgoland, Germany

Bernard Castelein / Lesser black-backed gull (Larus fuscus), Helgoland, Germany

Bernard Castelein / Northern gannet (Morus bassanus) flying with seaweed in beak, Helgoland, Germany

Bernard Castelein / Young grey seal (Halichoerus grypus) lying on sand, Helgoland, Germany

Bernard Castelein / Eider duck (Somateria mollissima) female with chicks, Helgoland, Germany

Bernard Castelein / Grey seal (Halichoerus grypus) lying on the shore, Helgoland, Germany

Bernard Castelein / Oystercatcher (Haematopus ostralegus) and seals on a beach, Helgoland, Germany

Bernard Castelein / Grey seal (Halichoerus grypus) holding fin up, Helgoland, Germany

Bernard Castelein / Oystercatcher (Haematopus ostralegus) feeding on beach, Helgoland, Germany

Bernard Castelein / Oystercatcher (Haematopus ostralegus), Helgoland, Germany

Bernard Castelein / Northern gannet (Morus bassanus) flying downwards, Helgoland, Germany

Bernard Castelein / Common seal (Phoca vitulina) on shoreline, Helgoland, Germany

Bernard Castelein / Grey seals (Halichoerus grypus) play-fighting, Helgoland, Germany

Bernard Castelein / Common seal (Phoca vitulina) lying on beach, Helgoland, Germany

Bernard Castelein / Grey seal (Halichoerus grypus) play-fighting, Helgoland, Germany

Bernard Castelein / Male eider duck (Somateria mollissima), Helgoland, Germany

Bernard Castelein / Grey seal (Halichoerus grypus) lying on shore, Helgoland, Germany

Bernard Castelein / Northern gannet (Morus bassanus) with seaweed in beak, Helgoland, Germany

Bernard Castelein / Northern gannet (Morus bassanus) in flight, Helgoland, Germany

Bernard Castelein / Grey seal (Halichoerus grypus) lying in surf, Helgoland, Germany

Bernard Castelein / Northern gannet (Morus bassanus) flying, Helgoland, Germany

Bernard Castelein / Grey seal (Halichoerus grypus) scratching head, Helgoland, Germany

Bernard Castelein / Northern gannet (Morus bassanus) hovering, Helgoland, Germany

Bernard Castelein / Wounded grey seal (Halichoerus grypus) (probably by a propeller), Helgoland, Germany

Dietmar Nill / Grey seal (Halichoerus grypus) pup on a beach in Helgoland, North Sea, Germany

Dietmar Nill / Grey Seal (Halichoerus grypus) juvenile in sand dunes, Helgoland, North Sea, Germany

Florian Graner / Sea anemone and polyps. Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) hauled out group resting, North Sea, Helgoland, Germany

Ingo Arndt / Common Seal (Phoca vitulina), North Sea, Helgoland, Germany

Ingo Arndt / Common Seal (Phoca vitulina) resting in shallow water, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) play fighting in shallows, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) play fighting in shallows, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) in shallows, play fighting, North Sea, Helgoland, Germany

Ingo Arndt / Common Seal (Phoca vitulina) resting in shallow water, North Sea, Helgoland, Germany

Ingo Arndt / Common Seal (Phoca vitulina) with radio transmitter on its back, North Sea, Helgoland, Germany

Ingo Arndt / Common Seal (Phoca vitulina) resting in shallow water, North Sea, Helgoland, Germany

Ingo Arndt / Common Seal (Phoca vitulina) resting in shallow water, North Sea, Helgoland, Germany

Ingo Arndt / Northern Gannet (Morus bassanus) flying, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) group resting with tourists in the background, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus), North Sea, Helgoland, Germany

Ingo Arndt / Northern Gannet (Morus bassanus) couple in courtship display, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) play fighting, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) play fighting, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) play fighting, North Sea, Helgoland, Germany

Ingo Arndt / Common Murre (Uria aalge) flock on nesting rock, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) pair play fighting, North Sea, Helgoland, Germany

Ingo Arndt / Black-legged Kittiwake (Larus tridactyla) couple on cliff nest, North Sea, Helgoland, Germany

Ingo Arndt / Common Eider (Somateria mollissima) portrait of a male, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) scratching on beach, North Sea, Helgoland, Germany

Ingo Arndt / Northern Gannet (Morus bassanus) with nesting material, North Sea, Helgoland, Germany

Ingo Arndt / Grey Seal (Halichoerus grypus) play fighting, North Sea, Helgoland, Germany

Ingo Arndt / Northern Gannet (Morus bassanus) flying, North Sea, Helgoland, Germany

David Tipling / Heligoland trap over trees used to trap birds for ringing, Fair Isle, Scotland, UK

Kerstin Hinze / Sanderling (Calidris alba) using bill to search for food in sand, Helgoland, North Sea, Germany

Kerstin Hinze / Sanderling (Calidris alba) running through water on the shore, Helgoland, North Sea, Germany

Ingo Arndt / Moon Jelly (Aurelia aurita) twelve centimeters, Helgoland, Germany

Ingo Arndt / Moon Jelly (Aurelia aurita) twelve centimeters, Helgoland, Germany

Ingo Arndt / Sea Gooseberry (Pleurobrachia pileus) one centimeter, Helgoland, Germany

Ingo Arndt / Zooplankton, algae fish and crab eggs, Copepods approximately one centimeter, Helgoland, Germany

Ingo Arndt / Sea Lettuce (Ulva lactuca) algae twenty one centimeters, Helgoland, Germany

Ingo Arndt / Shagrug Nudibranch (Aeolidia papillosa) length is two centimeters, Helgoland, Germany

Ingo Arndt / Shagrug Nudibranch (Aeolidia papillosa) length is two centimeters, Helgoland, Germany

Ingo Arndt / Shagrug Nudibranch (Aeolidia papillosa) length is two centimeters, Helgoland, Germany

Ingo Arndt / Barnacle-eating Onchidoris (Onchidoris bilamellata) two centimeters long, Helgoland, Germany