1C6 BRITISH BIRDS. 



interest and importance. In the young- of the Red Grouse, 

 for example, these feathers are more degenerate than in 

 the Common Fowl, or Turkey, since they lack a well- 

 defined axis for the supjjort of the barbs, and the same is 

 true, though to a less extent, of the Black Cock. Carried 

 a stage or two further we should get a semi-plume or 

 mjsoptyle structurally indistinguishable from a protoptyle, 

 and this is evidently what has happened in the case of the 

 Barn-Owl. In the Passerine birds the mesoptyle plumage 

 is even more degenerate and in many species is wanting 

 altogether, just as it is in most of the Picarian birds. 



Let us suppose that we are describing the nestlings of, 

 say, the Tawny and Barn-Owls, Kestrel, Pheasant, and 

 Cormorant. This might be done as follows : — 



Nestling-plumage (Tawny Owl). — Composed entirely of 

 jpre-pennoe. 



Specimen A, about three days old, with a ])rotoiityle 

 2)lumage of pure white. 



Specimen B, about eight weeks old, with a well-developed 

 Tnesoptyle plumage, buif coloured and barred with fine 

 transverse bars. Quill and tail feathers well developed. 



Nestling plumage (Barn-Owl). — Composed, entirely of 

 pre-pennoe. The nestling-plumage of this species is 

 composed simply of degenerate mesoptyles, which are pure 

 white in colour. 



Nestling plumage (Kestkel). — The nestling-plumage 

 of this bird is composed of pre-pennce and pre-plumulce, the 

 latter being far larger, and making up the bulk of the down. 

 Colour — white. Whether the pre-pennce represent pro- 

 toptyJes or mesoptyles is a matter for further investigation. 



Nestling plumage (Pheasant). — The nestling-plumage 

 is made uj) of pre-pemue only. Only the mesoptyle 

 plumage is developed, and this is marked by a broad dark 

 median band and two lateral bands running down the 

 back, etc., etc., etc. 



Nestling plumage (Cormorant). ^The nestling- j^lumage 

 of this bird is composed entirely oi protoptyles, and is black 

 in colour. 



