Cygnus Bechst., Orn. Taschenb., ii, p. 404 (note) (1803).
Type, Cygnus olor Edw.
The distinguishing feature of this genus is that of the subfamily, the very long neck: 23 or more cervical vertebrae as against less than 20 in other forms; the bill is of moderate size, raised at the base and of nearly equal breadth throughout; the nostrils are elliptical and placed about half-way down the bill; the lores are naked; the tarsi are short and stout and placed very far back; the wing is long, the first primary about half the length of the second and the second and third subequal and longest; the tail is short and well rounded.
Swans are to be found throughout the temperate and Subarctic regions of the world.
Key to Species.
A. Lores and triangular patch between forehead and gape yellow or orange-yellow, never black. No knob at base of bill.
a. Yellow on bill extending right up to the nostril and sometimes still further towards tip
of bill……………C. cygnus, p. 380.
b. Yellow never reaching to nostril and generally confined to somewhat circular patch on base. a1. Bill longer, broader but less high at the base in comparison Serrations hardly
visible on bill when closed……………C. minor, p. 382.
b1. Bill shorter, not so broad but compara¬tively high at base. Serrations visible along nearly whole length of bill when closed……………C. bewickii, p. 381.
B. Lores and triangular patch black. A knob at base of bill in adults……C. olor, p. 383.
* As the genus Fuligula is now united with Nyroca (which, moreover, is the earlier name and should, therefore, give the name to the subfamily) the name Fuligulinae cannot be employed.