237. Hydrochelidon hybrida.
THE WHISKERED MARSH-TERN.
Hybrida— B, mongrel, hybrid; because Pallas thought it like a hybrid between H. nigra and Sterna fluviatilis.
Male 10" to 11". Legs dull red. Bill lake. Forehead, crown, and nape black. White eye-line. Chin, cheeks, throat, vent, under tail-coverts and wing-lining white. Abdomen dull black. Upper tail-coverts and tail grey.— In winter: Front and round bill white. Beneath white. S.W., C, and S. Europe, Africa, Asia, to China and Australia. Three eggs (1.51 x 1.09), olive, spotted purple and brown. Breeds along the Danube and in the Orange River Colony, forming a curious but not the only instance of a bird nesting both north and south of equator. (J. 984. B. 1496.)
Also H. nigra. 9 1/2" to 10". The Black Tern. Legs red-brown. Bill black. Head and neck black. Mantle and wings slate. Breast and abdomen dark lead colour.— In winter: Forehead white, crown and nape mottled. Europe south of 60° N. lat., Africa. Not traceable in Asia beyond W. Turkistan.
H. surinamensis. 9 1/4". Similar to H. nigra, but abdomen deep black. Temperate N. America to S. America in winter.
Also the genus Phaethusia, with webs slightly indented. One species— P. magnirostris, 14 3/4". Legs olive, webs yellow. Bill yellow. Head and nape black, with narrow white line at base of bill. Mantle and tail slate-grey. Primaries dark brown, with whitish wedges on inner webs. Below white. S. America.
(ii.) Outer tail-feathers longest, pointed. (238-254.)