INTRODUCTORY NOTE *HI 



authorities, been freely consulted whenever necessary, and thus 

 two of the three largest collections of bird-skins in the world have 

 been available. Notwithstanding this, the private collections 

 of the writers have been found invaluable adjuncts, because they 

 contain many moulting birds and young birds which are 

 unfortunately still considered by most collectors to be hardly 

 worth preserving. 



It will be found that the various parts of the plumage are 

 described in a uniform order throughout, which should make 

 reference easy. The different plumages of each species are also 

 described in a definite order as follows : Adult male (and female 

 if different), winter, summer, Nestling (i.e. as soon as hatched), 

 Juvenile (i.e. the first covering of true feathers), First winter (i.e. the 

 plumage following the juvenile), First summer, Second, third, etc. 

 Winter and Summer, if different from the adult. The adult winter 

 plumage has been taken first for the full description, because this 

 is usually the most perfect plumage in that it is acquired by a 

 complete moult. Other plumages of the adult are usually ., a 

 modification of this plumage either by wear or else by partial 

 moult. All British birds have one complete annual moult, many 

 have a second partial moult, but few have two complete moults. 

 A special point has been made to give details of the periods and 

 extent of the moults of each species. 



MEASUREMENTS AND STRUCTURE. Under this heading it will be 

 found that all measurements are given in millimetres and centi- 

 metres, not only because the " International Rules " so advise 

 but also because one-tenth of an inch does not provide a small 

 enough division for scientific accuracy (especially in eggs), and a 

 smaller fraction in inches is clumsy. The comparative length of 

 the primaries given in every species will, it is thought, be found 

 useful, and this has never been systematically done before. 



Figures showing the various parts of a bird's plumage, and 

 how measurements are taken are given below, as well as a glossary 

 of terms and a millimetres and inches table. 



CHARACTERS AND ALLIED FORMS. In this section an indication 

 is given of how various subspecies differ, and their approximate 



