82 Wonders of the Bird World 



undoubtedly by a complete moult. Most of the species we 

 are familiar with as summer visitors moult their feathers 

 before undertaking their autumn migration, and in nearly 

 every case they cast their old feathers and go south with 

 perfectly renewed plumage. The young birds, though they 

 may be thickly spotted and differ from the adults in this 

 respect, as, for instance, does our Common Flycatcher (Musci- 

 capa grisola), leave us in a full dress indistinguishable from 

 that of the parent bird. The young of the Warblers, such 

 as the Willow-Warbler, ChifTchaff, Great Sedge-Warbler 

 and others, can only be distinguished from the old birds 

 in their winter habitats by showing a little more yellow 

 tinge on the under surface, and even this is not observable 

 in the following spring, when young and old return in 

 perfectly full plumage. This is, however, because the 

 Warblers have a spring moult also, and, before they 

 return to their northern breeding-haunts, they cast all the 

 feathers with which they departed, and return to us in the 

 freshest of new plumage. This is certainly true of our 

 familiar migrants, and Thrushes (Turdidce) can be dis- 

 tinguished from Warblers (Sylviidce) by the fact of their 

 having spotted young, and by their having only an autumn 

 moult, and not a spring moult as well. Thus our Robin 

 and Nightingale are Thrushes and not W r arblers, as they 

 have so often been called. An ordinary species, like 

 our Song-Thrush (Turdus musicus), begins its life with a 

 spotted plumage, and then moults in its first autumn to a 

 dress so like that of the old birds, that it is only by the 

 indication of small spots on the tips of the wing-coverts 

 that it can be determined as a bird of the year. The 

 Swallows, however, do not moult in the autumn like 

 other migrants, but leave Europe in the same plumage in 

 which they arrived in the previous spring, while the young 

 birds go south in the feathering they acquire before leaving 

 the nest. Thus the old birds depart in a very ragged 



