63 



KEY TO TERNS AND SKIMMERS (Cont.) 



8 Both webs of outer 4 primaries entirely dark; wing length 400-423 



mm; tarsus 40-46 mm. 9 



8' Outer web of outer 4 primaries dark, inner web white except for broad 

 dark stripe next to shaft (Fig. 24a); wing <395 mm; tarsus <36 mm. 10 



9 Wing coverts each with dark brown V bordered by white. 



CASPIAN TERN, immature 



9' Wing coverts pearly gray (primaries darker). CASPIAN TERN, adult 



10 Wing length 357-393 mm. 11 

 10' Wing <330 mm. 12 



11 Some wing coverts with dark outer portions. ROYAL TERN, immature 

 IT Wing coverts pearly gray. ROYAL TERN, adult 



12 Dark coloration in webbing of outer primaries very light, in 

 primaries 7-9 white of inner web grading gradually to dark area 



near shaft (Fig. 24b). 13 



12' Dark coloration in primary webbing very dark, forming a dark stripe 



near shaft very distinct from outer portion of inner web (Fig. 24a). 14 



13 Brown or buffy edgings to feathers of back and wing coverts. 



GULL-BILLED TERN, immature 



13' No buffy edgings on any feathers. GULL-BILLED TERN, adult 



14 Buffy edgings to feathers on back and wing coverts. 



ELEGANT TERN, immature 



14' No buffy edgings on any feathers. ELEGANT TERN, adult 



15 Very small; wing length <180 mm. 16 

 15' Wing 230-290 mm. 17 



