iv PREFACE TO THE SECOSD EDITION. 



For thuse wlio are already familiar with the use of analytical keys iu 

 works on natural history such instructions would of course be quite 

 superfluous ; but as some who possess the book may not have had pre- 

 vious experience with such " keys," the following directions are given 

 for their benefit : 



In the first place, it may be stated that the principle upon which 

 the keys are constructed is that of dichotomous antithesis. That is, 

 each character tested must conform to one or another phrase, there 

 being only one alternative. Therefore, if the characters mentioned 

 after a} do not fit the bird iu hand, everything following must be 

 ignored until (C is reached. Having found that the bird belongs to a^ 

 or a*, as the case may be, then the immediately following b^ is to be 

 tested, and so on until the ultimate division is reached and the bird 

 identified. 



The method may be more fully explained by selecting some par- 

 ticular species for identification ; and for better illustration we will 

 select one belonging to a mainly extralimital family, and therefore less 

 familiar to the student of North American birds. The bird is from 

 the State of Tamaulipas, Mexico, somewhat resembles a medium-sized, 

 thick-set flycatcher, but is evidently not a member of the TyrannidcB. 

 We will suppose that the person is a beginner, and does not even know 

 the Order to which the bird belongs. In this case it is necessary to 

 commence with the " Key to the Higher Groups," on page 1, which 

 begins as follows : " «\ Hind toe connected by web or membrane with 

 the inner toe." 



The bird in hand has the hind toe quite free from the inner toe; 

 therefore it must be sought for under " cc. Hind toe, if present, not 

 connected with inner toe," in regard to which character it agrees. 

 Then U^ nuist be tested. " I?'' says, " Nostrils tubular and feet 

 webl)ed." It has not tubular nostrils nor webbed feet, and therefore 

 it must belong to i", which says, " Nostrils not tubular, or else feet 

 not webbed," both of whicli alternatives fit the bird in question. Pro- 

 ceeding to " t'\ Cutting-edges of bill more or less distinctl}-- fringed 



