IDENTIFICATION OF A SPECIMEN IN HAND 27 



THE SECOND STEP 



When the subfamily to which the specimen belongs is known, the 

 second step is to decide upon the species, or at least to narrow down to 

 a few possibilities the number of species to which it may belong. This 

 is best accomplished by examination of the spread-wing, and by the use 

 of the Wing Key which follows. 



Before proceeding further with the identification it is necessary to 

 bear in mind the following points: 



Note A. The wing of the adult male and of the adult female is always con- 

 stant; it is the only feature of the plumage which does not vary in pattern 

 during any moult. The wing of the adult bird is, therefore, a positive guide 

 to the species. The spread wings of all the adults are illustrated on the 

 Colour Plates. 



Note B. The wing of the juveniles of both sexes in the autumn and until 

 after the first postnuptial moult during the following summer) is somewhat 

 different from that of the respective adults. The wings of the juveniles are not 

 illustrated on the Colour Plates, but the manner in which they differ from 

 those of the adults is detailed under "Description" of juvenile in the text. 

 As a general rule, in (a) the River and Pond Ducks, the wing of the juvenile 

 male resembles that of the adult male, and the wing of the juvenile female 

 resembles that of the adult female; in (b) the Diving Ducks, the wings of 

 the juveniles of both sexes resemble those of the adult female. 



Note C. In the Colour Plates the adult birds are illustrated in both full 

 winter plumage and during the autumn moult. Young birds of the year 

 are not illustrated, but (except for the wings) the juvenile male during 

 the autumn will correspond in plumage characters very closely to the adult 

 male at that season; the young female will be very similar to the adult fe- 

 male. 



Note D. It is sometimes difficult to distinguish with certainty between 

 some of the species (especially in the case of certain females). In all in- 

 stances of uncertainty consult "Specimen Identification" in the text which 

 deals with similarities and puzzling variations. 



Note E. The eiders and the mergansers are not included in the following 

 Wing Key as the bill characteristics of these groups provide ready means 

 of identification. 



It is now in order to proceed with the identification of the species. 



Measure the wing (see fig. 24) from the "bend" to the tip of the 

 longest flight feather, and consult the Wing Key. Depending upon the 

 measurement of the wing, the specimen will classify as group (1) "Wing 

 small" or group (2) "Wing large." 



An examination of the wing-coverts or the speculum, as the case 

 may be, will now place the specimen in one of the further subdivisions 

 as shown on the Wing Key. 



