VOL. XIV.] LETTERS. 101 



(Dec. i8th, 1920, p. 856) Mr. J. S. Pratt states that he saw 

 a Swallow at \\'orthing on December 6th. 



The Altitude of Migratory Flight. — In connection 

 with our notice iantea, p. 165) of Col. R. Meinertzhagen's 

 paper on this subject, Mr. H. M. Wallis writes that while at 

 sea on August 2nd, 1914, off Boston Deep and out of sight of 

 land, he saw at 10.30 a.m. a red Homer approaching the ship 

 from the westward, flying rapidly just above the tops of the 

 waves. It rose to pass between the masts of the ship and 

 then dropped to its former level and continued on its course 

 due east. A second similar bird appeared soon after, but, 

 being drenched with rain, settled on the ship, where it 

 remained all day. This interesting observation shows that, 

 though trained to find their way by sight, a non-migratory 

 species like the Homing Pigeon can assume and keep a course 

 at such an altitude that sight can be of very little use to it. 



LETTERS. 



NE.STLING DOWNS OF HAWKS. 



To the Editors of British Birds. 



Sirs, — From Mr. Witherby'.s comments (antea, p. 154) on my Ibis 

 paper (October 1920), it is abundantly evident that the terms applied 

 to the study of feathers are not sufficiently precise. In my definition 

 of the word " plumula?," I describe it as " the small downy feathers 

 found in the adults of many birds." This being the case. I was certainly 

 wrong in loosely referring to the second generation of down in young 

 Hawks and Falcons as plumulse. In order to be exact this second 

 generation of downy feathers requires a name — a term corresponding 

 to mesoptile in the pre-penna; group of feathers. Mr. Witherby is 

 (juite right when he points out that this second generation of down is 

 longer and coarser than the ultimate growth of plumules, but his 

 experience differs from mine in regard to its colour. Although it is 

 drab or slightly dusky in some species examined by me (i.e., Milviis 

 and Circus), according to my notes in the majority it is white or whitish 

 (i.e., Falco, Aqitila and Circaetus). 



A fixed and definite nomenclature for the successive growths of 

 feathers is badly needed. In some birds, more or less perfect adult 

 feathers are acquired at once, whereas in others two or three successive 

 generations of structurally distinct feathers may be noted. Moreover, 

 further to complicate matters, in some species — the Hawks, for in- 

 stance—there ajipear simultaneously successive generations of what 

 ultimately develop into two quite distinct types of feathers : 

 Teleoptiles and Plumules. True, Mr. Pycraft has made an attempt 

 to classify what might be termed the Penna; Cxroup, his names being 

 respectively for the first, second and third generations : Protoptile, 

 Mesoptile and Teleoptile. The chief objection to this system of 



