INTRODUCTION. 19 



An opera-glass, if a sufficiently strong magnifier, or occasion- 

 ally a telescope, will be found very useful, as it enables one to 

 recognize a bird without disturbing it, and to distinguish colors, 

 when the object is distant, or at a great height among branches. 

 It is more difficult to distinguish colors just before or after 

 sunset than at other times of the day, particularly if they be ex- 

 posed to the sunlight. That hour should therefore be avoided. 



T. Of anatomy and details of structure I shall not here 

 speak at length, since they are not referred to in this volume 

 more often than convenience requires. 14 The bill consists of 

 two mandibles, the line between which is called the gape or 

 often the commissure. The true cere, which belongs only to 

 the parrots and birds of prey, is a thick skin which covers the 

 upper mandible at its base, and in which are the nostrils, 

 though often concealed by feathers. 



The principal wing-feathers are the primaries, which (with 

 perhaps exceptions) are always nine or ten, except in flight- 

 less birds, and which form the end or "point" of the wing. 

 They are the long outer feathers, of which the shafts (if the 

 wing be spread) are more or less parallel, forming an evi- 

 dent angle with those of the adjoining secondaries. A so- 

 called "spurious" primary is usually the first or outermost, 

 when very much shorter than the rest. (It differs from the 

 " bastard wing" or " spurious quills " in being a single feather 

 and beneath the second primary.) The "shoulder" of the 

 wing is the " bend " near its connection with the body. The 

 tail is even or square, rounded or forked, as viewed when 

 half-closed ; if slightly forked, emarginate, if very deeply 



14 The reader is referred for a full treatise to the introduction of Dr. Coues' 

 'Key to N. A. Birds." 



