Mr. R. B. Sharpe's Catalogue of Accipitres. 353 



The geographical range of H. leuconotus is stated by Mr. 

 Sharpe to be " North-Eastern and Southern Africa ; " but 

 it also extends to Senegal, an adult specimen from Bissao 

 being preserved in the Norwich Museum. There seems^ in 

 fact, to be but little, if any_, difference between the geo- 

 graphical ranges of H. leuconotus and H. ecaudatus -, and 

 Mr. Sharpe remarks that the former '' is perhaps the fully 

 adult bird " of the latter ; but in this view I am not dis- 

 posed to agree, as many specimens have been kept in con- 

 finement in this country, amongst which I have never heard 

 of one having changed from a rufous back to a cream-coloured, 

 or vice versa*. I ought, however, to add that in an adult 

 specimen of H. leuconotus, which I recently examined in the 

 Strickland Collection at Cambridge, there is a decided ap- 

 pearance of faded rufous on the tail, though not on the back. 



Von Henglin has some noteworthy remarks on this subject 

 in his ' Ornithologie Nord-Ost Afrika^s,^ vol. i. p. 80, of which 

 the following is a translation : — " Specimens with white back 

 and tail are found in the whole of Africa. Vierthaler ob- 

 served the transition through moulting from the red brown- 

 to the white-backed bird, whilst I have shot a newly-moulted 

 one of the last-named plumage the dorsal feathers of which 

 were onl^'^ partly grown, but these also showed the white 

 plumage. We also saw plainly, several times, pairs of the 

 white-backed variety. Most of the specimens we found on 

 the White Nile and in Kordofan were white-backed ; the 

 Abyssinian birds were all brown-backed." 



I venture to think that Vierthaler^s note, referred to in the 

 above extract, only implies that he had observed a specimen 

 in confinement to change from the immature brown plumage 

 to the white-backed adult dress, and not from the rufous- 

 backed adult plumage to the white-backed. The following is 

 a translation of Vierthaler^s memorandum on the subject, 

 which was made during his journey on the Blue Nile, and 

 which, it must be admitted, is not so precise as could be 



[* In the Zoological Society's Gardens are two red-backed specimens, 

 received in 1873, which show no signs whatever of change into th© 

 white-hacked form. — Edd.] 



SER. IV. VOL. II. 2 b 



