of colour, which is generally most conspicuous on the underparts. 

 lu the rare instances in which the upper parts are spotted in the 

 adult, the spots are less conspicuous in the young birds. In the 

 first autumn before migration, if a partial moult takes place, 

 it is simply a renewal of certain feathers by feathers of the same 

 colour, so that, in winter, birds of the year are generally easily re- 

 cognizable by a difference of shade in the colour, especially in that 

 of the underparts. This difference, however, is lost in tlie complete 

 moult which takes place in both adult aud young in spring, a moult 

 wliich usually takes place in March shortly before the sjiring migra- 

 tion begins. In autumn, usually in September, shortly before the 

 birds return to their winter quarters, a second annual complete 

 moult takes place in adult birds. The autumn plumage is usually 

 intermediate in colour between the spring plumage and that of the 

 bird of the year. Cuiiously enough, this peculiarity in the colour 

 of the immature bird, and in the subsequent moults which the plu- 

 mage undergoes, is correlated with the existence of scutellations on 

 the front of the tarsus. 



TuRDix^. The young in first plumage differ from the adult in 

 having the upper aud the underparts spotted, whether that is or is 

 not the case in the adult. Instead of two moults in the year, there 

 is only one, in auturau, the spring plumage being obtained by abra- 

 sion, or by casting the points of the feathers. Where any feathers 

 have become much worn by the spring, they are replaced by new 

 ones, but nothing approaching a complete moult is observable. 

 Under these circumstances the young birds would have to carry 

 their nestling plumage, or the greater part of it, until the second 

 autumn. To avoid this they have a complete moult, from immature 

 plumage to adult, in their first autumn before they migrate. Con- 

 sequently the winter pliimage of the young and adult is the same, 

 and they can generally only be distinguished by an isolated feather 

 here and there, generally on the wing-coverts or innermost secon- 

 daries, which have a pale tip as in the immature plumage. These 

 peculiarities of moulting appear in this group of birds to be alwaj's 

 associated with a lAa'in tarsus, except occasionally in very young 

 birds of one or two species. 



When sufficient facts have been accumulated to make a classifi- 

 cation of the Passeres possible, it is probable that the Muscicapidce 

 and the Timelii'ke will be all or most of them absorbed in the fami- 

 lies Tiirdiilce and St/lviidce, each of which may be again subdivided 

 into Turdine, Timeliine, and Muscicapine groups of genera or sub- 

 families. 



Subfamily SYLVIIN^. 



Key to the Genera. 



a. Tail containing twelve feathers. 

 a'. Axillaries yellow. 



a". Bill Pbyll()Sco),ine, more or less dark 



uudenieatb (see woodcut, page 37) . . 2. Phyli.oscopvs, p. 37. 



