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KEY TO TERNS AND SKIMMERS 



1 Basic color of upper surface of wings, back and hind neck dark brown, 

 black or dark charcoal-gray (tips of secondaries may be white) - 

 close in color to back of head, but sometimes with buffy feather 

 edgings. 2 



1' Basic color of upper wings, back and hind neck light gray, or 

 pearly to silver-gray; sometimes neck almost white, otherwise 

 much lighter than cap or back of head; sometimes with buffy feather 

 edgings. 7 



2 Wing length <225 mm; webbing extending only half way to end of toes 

 (Plate 37-2). 3 



2' Wing >270 mm; toes fully webbed. 4 



3 Brown edgings on wing coverts; belly white. BLACK TERN, immature 



3' Wing coverts entirely charcoal-gray; belly black or white. 



BLACK TERN, adult 



4 Wing length 270-300 mm; upper surface of wing entirely black or dark 

 brown except that coverts may have buffy tips; tarsus 20-25 mm. 5 



4' Wing 338-412 mm; secondaries broadly tipped with white; tarsus 



28-37 mm. 6 



5 Upper surface of wings entirely jet black; belly white. 



SOOTY TERN, adult 



5' Wing coverts with buffy tips; belly charcoal-gray. 



SOOTY TERN, immature 



6 Upper wing jet black except for white in secondaries (sometimes on 

 inner primaries). BLACK SKIMMER, adult 



6' Upper wing coverts with light tips, otherwise upper wing dark brown. 



BLACK SKIMMER, immature 



7 Wing length > 295 mm; tarsus > 27 mm. 8 

 7' Wing < 290 mm; tarsus < 24 mm. 15 



