PLAN OF THE WORK xv 



stand the use of the keys. At first sight they will, no doubt, appear 

 confusing, but in reality they are exceedingly simple. The system 

 upon which they are arranged may be mastered in a few minutes, and 

 you will then be surprised at the ease and rapidity with which, even 

 in large families, you can "run a bird down." 



The Key to Families. The scheme of this key which, since its 

 appearance in the first edition of the "Handbook," has been so widely 

 adopted, originated with Ernest Thompson Seton. The key here 

 presented is, with some modifications and expansions, based on one 

 contributed by Mr. Seton at a time when he was expected to be a joint 

 author of this work. Strictly speaking this is not one key but a series 

 of keys, one under each order. The orders are placed in a natural 

 sequence, that is, we begin with the oldest, or lowest, forms of birds, 

 Loons, Grebes, etc., and end with the most highly developed ones, 

 Thrushes, Bluebirds, etc. Two main divisions are given: first, Water 

 Birds; second, Land Birds. In no case will it be difficult to decide in 

 which of these groups a bird belongs. Now glance over the illustra- 

 tions, and select the one which you think most nearly resembles the 

 bird you are identifying. At each step, test your decision by reading 

 the brief diagnoses of orders and families. In this way you may readily 

 place your bird in its proper family. 



The Keys to Species. If a bird always wore the same plumage, it 

 would be a comparatively easy matter to place it in a certain section 

 of a key and keep it there. But, unfortunately, not only are the males 

 and females of the same species frequently quite unlike, and the young 

 different from either, but their plumages may vary with the season. 

 Furthermore, an individual of a given species may not only wear two 

 very different costumes, but, in doffing one for another, he does it 

 gradually, and, in the meantime, appears in ' hanging or transition 

 plumage. 



For this reason it has been customary to base keys on only adult 

 males. Such keys do very well in the nesting season, when birds are 

 in song, and when males constitute probably nine-tenths of the birds 

 one sees. But at other times of the year young birds outnumber the 

 old ones, and the adults themselves may lose their breeding plumage 

 and wear quite a different one. I have, therefore, attempted to make 

 keys which will identify a bird in any plumage. To do this, it was 

 necessary to use many more specimens than there were species. For 

 example, the key to our some 40 species of Warblers is based on 110 

 specimens, representing as many phases of plumage. 



With identification as the sole end in view, I have, in the keys, 

 abandoned all attempts to follow the current system of classification, 

 and, taking color as the most tangible character, have to a great extent 

 arranged the species on this character alone. The result, from the sys- 

 tematist's standpoint, is most unnatural. Species of different genera 

 are brought into the same subsections, and the more variable species 

 may be placed in several widely separated sections. 



