*IV INTRODUCTORY NOTE 



breeding-range is noted. These brief details will, it is thought, be 

 found useful by those who are travelling out of the British Isles. 

 There follow the chief characteristics of the species for the purpose 

 of distinguishing it rapidly from any other on the British list with 

 which it might be confused. This section may be used conveniently 

 with the Keys, and it is hoped that it will be a useful assistance 

 to identification. 



FIELD-CHARACTERS. In this section a discriminating analysis has 

 been made of the bird's appearance, flight, notes, and song, and 

 other characteristic habits observable in the field. Comparative 

 notes are also given to show how it differs from other birds which 

 might appear similar, unless the distinguishing characters were 

 observed. It is often not possible to give an infallible guide to 

 identification in the field : moreover, different observers note 

 different characteristics, and it is often very difficult to put into 

 words exactly how one identifies a bird in the field. The chief 

 aim of the writers of this section has been to indicate the points 

 on which attention should be concentrated. 



BREEDING-HABITS. Here the salient facts have been briefly 

 summarized, but owing to exigencies of space, only the more typical 

 nesting sites and materials are described. Similarly with the eggs, 

 it would be impossible to give details of each variety, but the 

 usual types are described ; and where known some details as to 

 breeding-season, incubation period and share of the sexes are added, 

 as well as the number of broods reared in the season. 



FOOD. For this section, besides the modern works of Newstead, 

 Collinge, Florence and others, which treat of the subject from the 

 economic point of view, the results of post-mortem examinations 

 which have been published in various zoological journals during the 

 last seventy years have been tabulated and briefly summarized. 



DISTRIBUTION. This is divided into two sections, one devoted 

 to the British Isles, and the other "Abroad." The latter is in 

 general terms, while the former is detailed, especially in species 

 which are local, rare, or limited in their distribution. Refer- 

 ences are given to the original records of " vagrants " which have 

 been observed on only a few occasions, while in other cases a more 



