Hanne & Jens Eriksen / Lesser crested tern {Thalasseus bengalensis} flock on beach, large gulls and waves in background, Socotra, Yemen

Tony Wu / Greater crested tern (Thalasseus bergii) feeding on Sardine, Tonga.

Steven David Miller / Australian sea lion (Neophoca cinerea) male basking on beach with Great crested terns (Thalasseus bergii) in foreground. Seal Bay Conservation Park, Kangaroo Island, South Australia.

Ann & Steve Toon / Swift terns (Thalasseus bergii) Luderitz, Namibia.

Jiri Lochman / Crested tern (Sterna bergii) juvenile entangled in a fishing line, likely cut off by a fisherman after the bird swallowed the hooked bait. Australia.

Jiri Lochman / Crested tern (Sterna bergii) juvenile, entangled in a fishing line, likely cut off by a fisherman after the bird swallowed the hooked bait Australia.

Franco Banfi / Greater crested terns (Thalasseus bergii) on a strip of sand with the MV Atlantis Azores liveaboard boat in distance, Tubbataha Reef Natural Park, UNESCO World Heritage Site, Sulu Sea, Cagayancillo...

Franco Banfi / Greater crested terns (Thalasseus bergii) on a strip of sand with the MV Atlantis Azores liveaboard boat in distance, Tubbataha Reef Natural Park, UNESCO World Heritage Site, Sulu Sea, Cagayancillo,...

Rob Drummond/ BIA / Greater Crested Tern (Thalasseus bergii) juvenile flying, Victoria, Australia

Charlie Summers / Greater crested tern (Thalasseus bergii) flying against a backdrop of the South Atlantic Ocean. Lambert's Bay, South Africa.

Oriol Alamany / Greater crested terns (Thalasseus bergii) along shore of Seventy Five Mile beach, Fraser Island UNESCO World Heritage Site. Queensland, Australia, November.

Martin Gabriel / Lesser crested tern (Sterna bengalensis) and Common Tern (Sterna hirundo), La Digue Island, Republic of Seychelles