INTRODUCTION. 17 



branches. It is harder to distinguish colors just before or 

 after sunset than at other times of the day, particularly if 

 they be exposed to the sunlight. That hour should therefore 

 be avoided.* 



It will be found very advantageous to make observations 

 continuously from day to day, as one will not only see many 

 birds who otherwise would escape him, but will acquire an 

 invaluable familiarity with their little characteristics (which 

 one may often think insignificant), and so an intimacy with 

 the birds themselves, which will enable h^im, for instance, to 

 detect the presence of the Brown Creepers by their shrill and 

 slightly tremulous tsip, where another person might require 

 more certain indications or more impressive evidence. More- 

 over, one will find that intimacy suffers from interruption, and 

 that knowledge is easily lost, however thoroughly gained. 

 Therefore, one may chance to find a familiar song no longer 

 associated with any bird. On the other hand, those who in 

 studying nature are obliged to do so at intervals will be sur- 

 prised at the amount of pleasurable acquaintance which they 

 can form with her at odd moments. There are few places 

 where birds cannot be studied to advantage, not excluding the 

 hearts of our cities, where may be found Creepers, Nuthatches, 

 Titmice, Warblers, Vireos, Flycatchers, Shrikes, etc., some- 

 times even Hawks. Finally, it is to be remembered that 

 birds are frequently erratic, and that observations on their 

 abnormal habits are, as a rule, interesting observations rather 

 than important discoveries, f 



§ 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.!^ 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 



* Gray days are trying. — W. B. " The reader is referred for a full 



t This last para^aph appeared on treatise to the introduction of Dr. 



p. 443 of the Appendix of the first Coues's Key to N. A. Birds. 



edition. — W. B. 



