KEY TO THE WATER BIRDS OF FLORIDA. 147 
Length, 14; Wing, 12; Tail, 5.50; Bill, 1.40; Tar- 
sus, 1.30. Forehead not white; crown, includ- 
ing forehead, black; upper parts pearl gray ; under 
parts white; bill comparatively short and thick; 
bill and feet black, Gelochelidon nilotica. 
Gull-billed Tern. See page 194 
Length, 9.50; Wing, 8.30; Tail, 3.60; Bill, 1.10; 
Tarsus, .7o, Adult in summer — under parts black. 
Adult in winter — under parts white; bill black ; 
feet dusky brown. Hydrochelidon nigra surina- 
mensis. 
Black Tern. See page 199 
Length, 9.25; Wing, 7: Tail, 3.50; Bill, 1.20; Tar- 
sus, 65. Under parts white ; bill and feet yellow. scterna antillarum. 
Least Tern. See page 197 
FamMIty RHYNCHOPID/E. SKIMMERs. 
Rhynchops nigra. 
Length, 18 to 20; Wing, 15; Tail, 5.50; Bill (cul- 
men), 2.70; Gonys, 4.25. Bill thin, knife-like, 
lower mandible the longer, basal half of bill 
vermilion red, blackish at tip. General plumage 
black, white beneath. .Rhynchops nigra. 
Black Skimmer. See page 200 
