Robin Chittenden / Caspian tern (Hydroprogne caspia) in flight, Western Division, Gambia, March

Robin Chittenden / Caspian Tern (Hydroprogne caspia) in flight, Western Division, Gambia, March

Barry Mansell / Caspian tern (Hydroprogne caspia) in breeding plumage, Tampa Bay, Florida, USA, April

Barry Mansell / Caspian tern (Hydroprogne caspia) in breeding plumage, Tampa Bay, Florida, USA, April

B&S Draker / Caspian Tern (Hydroprogne caspia) immature standing in shallow water with fish in its beak. Sinton, Coastal Bend, Texas, USA.

Andrew Walmsley / Adult Caspian tern (Hydroprogne caspia) feeding fish to chick, New Zealand, January

Hanne & Jens Eriksen / Caspian tern {Hydroprogne caspia} adults with chick, Turkey

Hanne & Jens Eriksen / Caspian tern {Hydroprogne caspia} two in flight, digitally manipulated, USA

David Tipling / Caspian tern (Hydroprogne caspia) in flight calling, Salton Sea, California, USA, April

Hanne & Jens Eriksen / Caspian tern (Hydroprogne caspia) in flight. Khawr Ghawi, Oman.

Hanne & Jens Eriksen / Caspian tern (Hydroprogne caspia) at low-tide. Khawr Ghawi, Oman.

Tom Marshall / Caspian tern (Hydroprogne caspia) adult calling. Lake Ellesmere. Canterbury. New Zealand, October

Tom Vezo / Caspian Tern (Hydroprogne caspia) flying, South Padre Island, Texas

Tom Vezo / Caspian Tern (Hydroprogne caspia) on beach, South Padre Island, Texas

Tom Vezo / Caspian Tern (Hydroprogne caspia) flying, South Padre Island, Texas

Tom Vezo / Caspian Tern (Hydroprogne caspia) calling, South Padre Island, Texas

Tom Vezo / Caspian Tern (Hydroprogne caspia) pair on beach, South Padre Island, Texas

Tom Vezo / Barn Swallow (Hirundo rustica) chicks in nest, southeast Arizona

Bengt Lundberg / Caspian terns {Hydroprogne caspia} breeding colony on island in Baltic sea, Sweden

Rolf Nussbaumer / Immature Caspian tern {Hydroprogne caspia} stretching wings, Welder Wildlife Refuge, Sinton, Texas, USA.

Rolf Nussbaumer / Immature Caspian tern {Hydroprogne caspia} bathing in water, Welder Wildlife Refuge, Sinton, Texas, USA.

Rolf Nussbaumer / Immature Caspian tern {Hydroprogne caspia} Welder Wildlife Refuge, Sinton, Texas, USA.

Keith Scholey / Caspian Tern (Hydroprogne caspia) calling in flight, Gulf of Suez Desert Islands, Egypt

Bengt Lundberg / Caspian tern calling, Sweden (Hydroprogne caspia)

Dave Watts / Caspian tern in flight {Hydroprogne caspia} Tasmania, Australia.

Dave Watts / Caspian tern {Hydroprogne caspia} Tasmania, Australia.

Gerry Ellis / Caspian Tern (Hydroprogne caspia) territorial displaying at nest site, mouth of Columbia River, Oregon

Mitsuaki Iwago / Caspian Tern (Hydroprogne caspia) nesting colony, Australia

Hanne & Jens Eriksen / Caspian terns and chick {Hydroprogne caspia} Karine Golu, Turkey

Dietmar Nill / Caspian tern (Hydroprogne caspia) calling in flight, Gambia, West Africa

Mike Wilkes / Caspian tern (Hydroprogne caspia) flying over water, fishing, The Gambia, December

Mike Wilkes / Caspian tern (Hydroprogne caspia) flock at water, The Gambia, December

Onne van der Wal / Caspian terns (Hydroprogne caspia) lined up on the beach, Belize.

Onne van der Wal / Caspian terns (Hydroprogne caspia, formerly Sterna caspia), flying off the coast of Belize.

Tom Vezo / Caspian Tern (Hydroprogne caspia) taking flight, South Padre Island, Texas