INTRODUCTION. 



stretched at full length do not afPord any correct idea of its relative 

 size as a living bird. 



Next, as to form and colour. In order to make the description 

 intelligible, some knowledge is essential of the names usually applied 

 to the various parts of a bird, and to the feathers which cover them. 

 The diagram which forms the frontispiece to this work, with the 

 references, will I hope be found useful as an explanatory index to 

 the terms commonly used in describing a bird. The bird selected 

 for the outline is our common Harrier {Circus f/ouldi). The technical 

 ierms may be multiplied to almost any extent, but for the sake of 

 simplicity I have indicated those only of which a knowledge is abso- 

 lutely necessary. 



The definition of colours iii tlicir endless diversity of tone and 

 shade is perhaps the most difficult part of the task, owing to there 

 being no recognized or commonly-received standard of nomenclature. 

 Every naturalist has, to some extent, a standard of his own, and we 

 repeatedly find different terms used by different writers to express the 

 same particular idea of colour and shade. There is less danger of 

 inconvenience or c(nifusion from this cause in a large establishment 

 like the British Museum, or the Natural History Museum at the 

 Jardin des Plantes, where all deseribers have daily access to certain 

 well-known types, and where, in consequence, there is a common under- 

 standing as to what is intended to be expressed by such stock terms as 

 ''ashy," "dusky," "cinereous," "rufous," "fulvous," "olivaceous," and 

 the like. But the fiexibility of our laiiguage enables a describer, by the 

 exercise of a little skill and judgment, and the free use of qualifying 

 adjectives, to express with precision almost every shade of colour by 

 the use of such compound words as " clear brownish-grey," " delicate 

 purplish-grey," &c., Avith the help also of the comparative term, as 

 for example, " darker towards the base," or " lighter towards the tip." 

 A good deal oL' practice, however, in describing colours and their dis- 

 tribution is necessary to make an expert in the art, so that a written 

 description may have the effect of bringing the object described 



