Genus STERNA.
Sterna Linn., Syst. Nat., 10th ed. i, p. 137 (Jan. 1758).
Type by sub. desig., Sterna hirundo Linn.
This genus has been split up into very many genera by various authorities ; by some practically a genus is given for every species. Most of these genera are founded on very trivial characteristics and seem quite unnecessary, only making the task of the student more difficult, whilst adding nothing to the science of ornithology. A doubtful exception is that of Sterna aurantia, which has been separated as a genus, Seem, on account of its stouter bill. This is, however, only a question of degree and I retain it in Sterna.
In this genus the bill is normally rather long, slender and straight and more or less compressed; the tarsus is shorter than the middle toe and claw; the feet are small and fully webbed; the wings are long and pointed, the first primary longest; the tail is always deeply forked but the length of the attenuated, lengthened outer feathers varies greatly.
Terns are found all over the world and are strongly represented in India, where we have ten species which are again divided into many geographical races.
Key to Species*
A. Mantle grey.
a. Crown black during the breeding-season.
a1. Wing over 200 mm.
a2. Tarsi yellow or red.
a3. Bilf orange-yellow.
a4.. Bill stout; wing over 250 mm.; abdomen white……………S. aurantia, p. 125.
b4. Bill slender; wing under 240 mm.; abdomen black in the breeding-season ……………S melanogaster, p. 127.
b3. Bill deep or dusky red. c4. Lower parts deep vinaceous-grey……………S. repressa, p. 128.
d4. Lower parts pale grey or white; outermost rectrices with dark grey outer webs……………S. hirundo, p. 129.
e4. Lower parts white or rosy; outer¬most rectrices nearly all white……………S. dougalli, p. 132.
b2. Tarsi blackish……………S. h. longipennis, p. 131,
b1. Wing under 200 mm……………S. albifrons, p. 135.
b. Crown always white, nape and line through eye black; bill black; tarsi dark brown……………S. sumatrana, p. 139.
B. Mantle dark brown,
c. Wing under 265 mm. ……………S. anaetheta, p. 141.
d. Wing over 275 mm……………S. fuscata, p. 143.
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