Saturday, September 28, 2013

Caspian vs. Royal Tern

I find Caspian Terns (below) and Royal Terns (above) to be tricky to tell apart. One field mark is the bill color: orange-red in the Royal, dark red in the Caspian. The trouble is that the Caspian’s bill color can vary, especially with different lighting and depending on the bird’s age. Note the dark tip on the Caspian Tern’s bill. The crowns often distinguish the two. Royal crowns tend to be white with a narrow black band across the sides of the face. Even as juvenals, Caspian Terns do not have as much white in the crown. Breeding Royal Terns, however, have black crowns.
The situation is less confusing in North America's interior, where only Caspian Terns are normally encountered (either as breeding birds or as migrants). Royal Terns almost never stray inland, keeping instead to the coasts of the Atlantic, Gulf of Mexico, Gulf of California and southern California. The Royal Tern in this blog was photographed on Florida's Atlantic Coast; the Caspian was in costal Texas.

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