Bence Mate / Caspian gulls (Larus cachinnans) juveniles fighting, Lake Csaj, Kiskunsagi National Park, Pusztaszer, Hungary. March.

David Kjaer / Yellow-legged Gull (Larus cachinnans) & two Juvenile Herring Gull (Larus argentatus) catching fish and fighting, Poland

Hanne & Jens Eriksen / Caspian tern (Hydroprogne caspia) with open beak, in shallow water. Oman, March.

John Chan / Caspian tern (Hydroprogne caspia) plunge diving near a group of Elegant terns (Thalasseus elegans) gathering at breeding grounds, Southern California, USA, March.

Loic Poidevin / Caspian gull (Larus cachinnans) perched on tree stump eating fish caught by Sea eagle. Black Sea, Danube Delta, Romania. May.

Sylvain Cordier / Caspian gull (Larus cachinnans) in flight, Socotra Island UNESCO World Heritage Site, Yemen.

Jussi Murtosaari / Caspian tern (Hydroprogne caspia) with fish prey, Finland, April.

Andy Trowbridge / Caspian Tern (Sterna caspia) in flight. Lake Forsyth, Banks Peninsula, Canterbury, New Zealand. August.

Andy Trowbridge / Caspian Tern (Sterna caspia) in flight. Ashley River, Canterbury, New Zealand. August.

Martin Gabriel / Hundreds of Heuglin's gulls (Larus heuglini) and Caspian gulls (Larus cachinnans) sourround fishermen as they land their catch, Salalah, Sultanate of Oman, February.

Hanne & Jens Eriksen / Caspian tern (Hydroprogne caspia) in flight looking for food, Oman, August

Hanne & Jens Eriksen / Caspian tern (Hydroprogne caspia) in flight with fish, Oman, November

Claudio Contreras / Caspian tern (Sterna caspia) in flight, El Vizcaino Biosphere Reserve, Baja Califonia Peninsula, Mexico, May

Avi Meir / Caspian Gull (Larus cachinnans) taking flight, Eilat, Israel

Hanne & Jens Eriksen / Caspian tern (Hydroprogne caspia) juvenile calling for food from adult, Oman, February.

Mike Wilkes / Caspian tern (Sterna caspia) catching fish, Tanji Beach, Gambia, West Africa.

Mike Wilkes / Caspian terns (Sterna caspia) resting on beach, Tanji Beach, Gambia, West Africa.

Mike Wilkes / Caspian tern (Sterna caspia) catching fish, Tanji Beach, Gambia, West Africa.

Mike Wilkes / Caspian tern (Sterna caspia) feeding on fish, Tanji Beach, Gambia, West Africa.

Mike Wilkes / Caspian tern (Sterna caspia) flying over beach, Tanji Beach, Gambia, West Africa.

Hanne & Jens Eriksen / Caspian tern (Sterna caspia) in flight, Oman, January

Wild Wonders of Europe / Lundgren / Caspian gull (Larus cachinnans) and White pelican (Pelecanus onocrotalus) perched, waiting for nearby fisherman to empty his nets, Danube Delta, Romania, June.

Loic Poidevin / Caspian terns (Hydroprogne caspia), British Columbia, Canada, June.

Ralph Martin / Caspian Gull (Larus cachinnans), Baden-Wurttemberg, Germany

Juan Manuel Borrero / Illustration of seagulls. Caspian Gull (Larus cachinans), Audouinas Gull (Larus audouinii), Common Black-headed Gull (Chroicocephalus ridibundus). Pencil, watercolor and pastel illustration

Grzegorz Lesniewski / Yellow Legged Gull/Caspian Gull (Larus cachinnans) nest with eggs. Vistual River, Mazovia, Poland, May.

Grzegorz Lesniewski / Yellow Legged Gull/Caspian Gull (Larus cachinnans) chicks in nest. Vistual River, Mazovia, Poland, May.

Grzegorz Lesniewski / Yellow Legged Gull/Caspian Gull (Larus cachinnans) chick hatching. Vistual River, Mazovia, Poland, May.

Pete Oxford / Caspian Gull (Larus cachinnans) profile, Gibraltar, United Kingdom

Nick Upton / Juvenile Yellow legged gulls (Larus cachinnans) chasing Sardine / European pilchard (Sardina pilchardus) as it leaps out of sea in attempt to escape. Between Isle of Lesbos /Lesvos, Greece and Turkey....

Nick Upton / Yellow legged gull (Larus cachinnans) in flight between Isle of Lesbos / Lesvos, Greece and Turkey. August

Nick Upton / Juvenile Yellow legged gull (Larus cachinnans) in flight at sunset, between Isle of Lesbos / Lesvos, Greece and Turkey. August

Nick Upton / Yellow legged gull (Larus cachinnans) flying low over sea while fishing for Sardines / European pilchards (Sardina pilchardus) between Isle of Lesbos, Greece and Turkey. August

Nick Upton / Yellow legged gull (Larus cachinnans) in flight between Isle of Lesbos /Lesvos, Greece and Turkey. August

Nick Upton / Yellow legged gull (Larus cachinnans) in flight, between Isle of Lesbos /Lesvos, Greece and Turkey. August

Nick Upton / Yellow legged gull (Larus cachinnans) chasing Sardine / European pilchard (Sardina pilchardus) leaping out of sea in attempt to escape. Between Isle of Lesbos / Lesvos, Greece and Turkey. August

DAVID TIPLING / Flock of Yellow legged gulls (Larus cachinnans) flying over rough sea, Black Sea, Bulgaria

DAVID TIPLING / Yellow legged Gull {Larus cachinnans} in flight, Lake Kerkini, Greece.

DAVID TIPLING / Yellow legged Gull {Larus cachinnans} in flight, Lake Kerkini, Greece.

Robin Chittenden / Caspian gull (Larus cachinnans) in flight, Dobrogea, Tulcea, Danube Delta Romania, September.

Konstantin Mikhailov / Yellow legged gull (Caspian gull) {Larus cachinnans} Black sea

Robin Chittenden / Caspian tern (Sterna caspia) in flight. Hickling Broad NWT, Norfolk, UK. May.

Andy Trowbridge / Caspian Tern (Sterna caspia) in flight, diving for prey. Lake Ellesmere, Canterbury, South Island, New Zealand.

Robin Chittenden / Caspian gull (Larus cachinnans) resting on beach outskirts, Norfolk, UK. October.

Angelo Gandolfi / DELETE Yellow-legged gulls (Larus cachinnans) patrol the storm waves in search of food at Camogli village, Liguria, Italy. Composite image.

Jussi Murtosaari / Caspian tern (Hydroprogne caspia) in flight. Kikkosalmi, Finland. May.

Marie Read / Caspian terns (Sterna caspia), aggressive interaction between adult (facing viewer) and juvenile, Cayuga Lake, Ithaca, New York, USA, August.

Marie Read / Caspian terns (Sterna caspia), juvenile (left) begging from adult in late summer, Cayuga Lake, Ithaca, New York, USA, August.

Marie Read / Caspian terns (Sterna caspia), adult arrives with fish to feed begging juvenile, late summer, Cayuga Lake, Ithaca, New York, USA, August.

Bernard Castelein / Caspian tern (Sterna caspia) flying with shell in beak, probably a juvenile play fishing objects from water surface. Allahein River, Gambia.

Bernard Castelein / Caspian tern (Sterna caspia) flying over water. Allahein River, Gambia.

Bernard Castelein / Caspian tern (Sterna caspia) stretching wings before taking off. Allahein River, Gambia.

Jussi Murtosaari / Caspian gull (Larus cachinnans), juvenile in flight, Finland, August.