W. p. PVCRAFr : NESTLING BIRDS. 



163 



"under-fur" of 'down in adult life. But they do not 

 occur in all species which possess such down. The 

 nestling-down of the Duck, for instance, is made up 

 entirely of pre-pennce. 



It is impossible to distinguish in any given nestling 

 between pre-plumulce and pre-pennce, except in individuals 

 which are just developing teleoptyles or contour-feathers, 

 when, in addition to the downy-tufts which will in such 



Fig. 3. — A Fre-jienna of a Barn-Owl, disintegrated, and being replaced 

 by a Contour-Feather. 



birds be found adhering to the tips of the contour- 

 feathers, as shown in Fig. 3, there may be found similar 

 tufts adhering to the tips of the budding adult down- 

 feathers. 



But the study of the nestling-down embraces more 

 curious facts than these, and happily all that are essential 

 are illustrated in the birds of our own Islands. These 

 facts are as follows. 



