Manuel Gracia / Whiskered tern (Chlidonias hybrida) chick falling asleep whilst standing in nest, Donana National Park, Sevilla, Spain.

Manuel Gracia / Whiskered tern (Chlidonias hybrida) preening whilst standing in nest, Donana National Park, Sevilla, Spain.

Hermann Brehm / Three Whiskered terns (Chlidonias hybrida) mobbing Grey heron (Ardea cinerea) which is crossing breeding colony. Hungary. July.

Hermann Brehm / Whiskered tern (Chlidonias hybrida) in flight. Hungary. July.

Hermann Brehm / Whiskered tern (Chlidonias hybrida) perched on reed. Hungary. July.

Manuel Gracia / Whiskered tern (chilidonias hybrida) adult flies into frame with dead frog (Anura sp.), prey is passed to other adult which is then fed to one of the begging chicks on the nest, one of the adult leave...

Gerrit Vyn / Black tern (Chlidonias niger) hunting over water in prairie wetland for emerging midges (Chironomidae) Medicine Lake National Wildlife Refuge, Montana, USA. June.

Tui De Roy / Brown noddy (Anous stolidus) calling, with Sally-lightfoot crab (Grapsus grapsus) on rock face, Isabela Island, Galapagos, South America.

John Chan / Elegant terns (Thalasseus elegans) diving and streaking which triggers the flock to take flight in unison, an example of flocking behavior, Bolsa Chica Ecological Reserve, Southern California, USA Mar...

John Chan / Elegant terns (Thalasseus elegans) gathering at mussel bed during breeding season, one hovering tern has a mussel clamped to its foot, a common mishap caused by stepping on an open mussel, Bolsa Chica...

John Chan / Elegant terns (Thalasseus elegans) gathering at breeding grounds take flight and return in unison, an example of flocking behavior, Bolsa Chica Ecological Reserve, Southern California, USA, March.

John Chan / Elegant terns (Thalasseus elegans) gathered at breeding grounds taking flight in unison, an example of flocking behavior, Bolsa Chica Ecological Reserve, Southern California, USA, March.

John Chan / Elegant terns (Thalasseus elegans) gathering at breeding grounds take flight in unison, an example of flocking behavior, Bolsa Chica Ecological Reserve, Southern California, USA, March.

John Chan / Brown pelicans (Pelecanus occidentalis) gathering with Western gull (Larus occidentalis), Elegant terns (Thalasseus elegans), Snowy egrets (Egretta thula) , Great egrets (Ardea alba) and Great blue he...

John Chan / Snowy egrets (Egretta thula) stalking as Elegant terns (Thalasseus elegans) dive nearby during a feeding frenzy, Bolsa Chica Ecological Reserve, Southern California, USA, September.

John Chan / Brown pelicans (Pelecanus occidentalis) flock taking flight with Elegant terns (Thalasseus elegans) and Double-crested cormorants (Phalacrocorax auritus), during a feeding frenzy, Bolsa Chica Ecologic...

John Chan / Brown pelicans (Pelecanus occidentalis) gathered with Western gulls (Larus occidentalis), Elegant terns (Thalasseus elegans) and Double-crested cormorants (Phalacrocorax auritus) during a feeding fren...

Pal Hermansen / Whiskered tern (Chlidonias hybrida) pair in courtship. Danube delta, Romania. May.

John Chan / Forster's terns (Sterna forsteri) diving for fish, Bolsa Chica Ecological Reserve, Southern California, USA, August.

David Woodfall / Viking style building made for filming the TV Series 'The Vikings' built in Kilcoole Marsh , habitat for Little terns (Sterna albifrons) Republic of Ireland, June.