92 BRITISH BIEDS. 



in the size of it. Mr. John Cordeaux, in the ' Birds of the Humber district,' 

 p. 64, says of the Rook, " A not uncommon variation shows a few white 

 feathers on the throat." I have a similar example in the Pied Wagtail. 



We all know well the seasonal changes affecting the throat in many 

 birds — black to white, and vice versd, — not to multiply instances, as in the 

 Razor-bill (^Alca tordd) ; but there appears to be, over and above this, a 

 tendency in a weakened constitution (from which I apprehend abnormal 

 variation in colour frequently springs) to attack this part more than some 

 others, as in man. 



Mr. Dresser has kindly lent me several specimens from his collection, 

 which I have figured side by side, viz. : — 



Ortyx texamis, variety (male), collected by himself: locality, San 

 Antonio, Texas, December 1863. Normal bird of the same 

 species (male), December 1863. Also 



Emberiza hortulana, normal male : Sweden. Emberiza casia, variety. 



Mr. Dresser has also been so good as to provide me with the following 

 translation from SevertzofF's 'Fauna of Turkestan '(TurkestanskieJevotnie): — 



" Severtzoff, speaking of Emberiza hortulana and E. casia, writes (Tur- 

 kestanskie Jevotnie, p. 118) as follows : — ' The latter is certainly not a mere 

 climatic race of the former, which in Turkestan is precisely similar to what 

 it is in Europe, having a greenish-grey head and a yellow throat. But we 

 have here two forms or races of E. casia, and in several instances I have seen 

 intermediate specimens showing a gradual passage between the two forms. 

 These forms are E. casia ; which has a whitish throat, and E. rufibarba, which 

 has a light-brownish throat ; but this difference in the throat is not of specific 

 value. E. hortulana inhabits the bushes, whereas E. casia inhabits the rocks 

 and stony hills. Both forms are common during the breeding-season, and 

 are not found far apart ; therefore the differences are not to be attributed to 

 climate.' " 



