( 186 ) 



ON THE DOWN-PLUMAGE AND MOUTH- 

 COLORATION OF SOME NESTLLNG BIRDS. 



BY 



C. B. TICEHURST, m.a., m.r.c.s., l.r.c.p., m.b.o.u. 



Of all the books which have been written on British birds 

 not one, as yet, has dealt satisfactorily with the question 

 of the sequence of plumages and, so far as I know, none give 

 even the barest description of the down or natal plumage of 

 even our commonest birds. 



Mr. Pycraft deplored this fact, and in the course of two 

 excellent articles {vide antea, Vol. 1, pp. 102 and 162) gave a 

 brief outline of the different kinds of down-plumage recognis- 

 able, and made some remarks upon their significance, at the 

 same time suggesting that further investigation into the 

 matter would be valuable. 



The sequence of plumages is a study which has long 

 interested me ; and I am certain that the collection of a large 

 amount of material in reference to this subject, as well as on 

 the coloration of the mouths of nestlings, as suggested by 

 Mr. Pycraft (c/. Vol. I., p. 129) would, when worked out on 

 comparative lines, yield some important results relating to the 

 question of morphological ornithology. 



As Mr. Pycraft has already explained (c/. Vol. I., p. 162) 



the different types of down, I shall here only state that in 



all the Passerine birds which I have examined, the type of 



down present is that of the pre-penna, and belongs to the 



mesoptyle generation. These pre-pennae, I need hardly 



remark, are not distributed all over the body, but are arranged 



in definite tracts. Further, the development of the pre-pennse 



in these tracts varies considerably in different genera, and 



even in the different species of the same genus. 



The inner supra-orbital tracts consist of few pre-pennse which 

 are situated above the eye on each side, and from thence 



