Large terns
Why bill color remains an important field mark for identifying Caspian and Royal Terns
Published: June 25, 2010
Contributing Editor David Allen Sibley discusses wingtip markings, forehead color, and overall shape of Caspian Tern and Royal Tern and tells why bill color remains an important field mark for identifying the species. Accompanying the article are paintings by Sibley showing the head of each species.
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