136 OBSERVATIONS ON MOTACILLA ALBA, LINN., 



that their differences should be clearly recognized and recorded 7 

 and for this we are all, whatever view we may take of the species 

 in question, very much indebted in this case to Mr. Brooks. 



A. 0. H. 



itefmiions mr IgtotatiUs atta, |m, m\b M|er Wagtails. 



By W. Edwin Bkooks, c.e .* 



The continuation of ray friend Mr. Seebohm's paper on the 

 Ornithology of Siberia in the Ibis for July 1878, is to me most 

 interesting, and he deserves the thanks of all ornithologists 

 for the number of valuable facts brought to light, which, but 

 for his energy and enthusiasm, might for ever have remained 

 unknown. Some of his identifications are most interesting, but 

 to one, which by the bye is also Mr. Dresser's, we must, I think? 

 most decidely object. 



A resemblance in some particulars does not prove identity? 

 but only close affinity. For identity, we must have the closest 

 correspondence in all material points. Now, suppose the adults 

 of any two recognized species were absolutely undistinguish- 

 able, and that the young of each did not correspond in all 

 material points, then the two birds are selon rnoi, as specifical- 

 ly distinct as any two with widely distinct adult plumages. I 

 am referring more particularly to small insectivorous birds and 

 Warblers, where we very seldom see variation, if at all. 



Amongst some genera there may be found slight specific 

 variation, but the species belonging to migratory genera, as 

 Motacilla, Budytes, Ant/ius, Ruiicilla, Sylvia, Acrocephalus, Lo- 

 custella, Phyllopneuste, and many others that might be mentioned,, 

 are wonderfully constant to their specific characteristics, eveu 

 though collected thousands of miles apart. Now Anthus trivi- 

 alis of India is absolutely undistinguishable from the same bird 

 in Europe. So also with Erythrosterna parva and Butalis 

 grisola of the two Continents. Budytes rayi of Yarkand is 

 exactly represented by Mr. Dresser's plate in i( Birds of Europe/' 

 and I have compared the Yarkand examples with European ones, 

 and there was not the faintest difference. Curruca rufa, the Com- 

 mon White Throat of the two Continents, corresponds most mi- 

 nutely. Eeguloides superciliosus, obtained near Calcutta, does 

 not differ a hair's breadth from the example shot by Mr. Han- 

 cock at Hartley on the Northumberland Coast. All the Ducks 

 agree marvellously well, and so do numbers of other species 

 that I might mention ; but I think I have cited enough to show 



* It is almost needless to repeat that the Editor is in no degree responsible for the 

 opinions of his contributors. 



