284 BRITISH BIRDS. [vol. viii. 



knowledge of birds is not yet sufficiently advanced for 

 definite rules to be laid down with regard to such questions 

 as the limitation of genera or the grouping of subspecies. 

 Some few months ago a most interesting paper was read by 

 Dr. P. R. Lowe at the British Ornithologists' Club on 

 "' Coloration as a Factor in Family and Generic Differentia- 

 tion " (see Ihis, 1915, pp. 320-346). In the discussion which 

 followed, most diverse opinions were expressed as to what 

 constituted generic characters. Genera are to a large extent 

 artificial and a matter of convenience, and it must follow 

 that their limitations are subject to personal opinion. The 

 following differences in the two lists are due to this cause, 

 the genera in the Hand-List being in capitals and those in 

 the B.O.U. List in itahcs : — Colceus — Corvus ; Spinus and 

 Acanthis — Carduelis ; Herbivocula — Lusciniola ; Cyano- 

 sylvia — Luscinia ; Hierofalco — ^Falco ; Astur — Accipiter ; 

 Chen — Anser ; Casarca — Tadorna ; Querquedula and Mareca 

 — Anas ; Netta and Glaucion — Nyroca ; Mergellus and 

 Lophodytes — Mergus ; (Edicnemus — Burhinus ; Eudromias 

 and JEgialitis — Charadrius ; Canutus — Tringa ; Tringytes 

 — Erolia ; Catharacta — Stercoraritjs. We see no necessity 

 for the smaller divisions adopted in the B.O.U. List, except 

 in the cases of Netta and " Glaucion" which we think are 

 justified. 



As to the grouping of subspecies, we have not space to 

 discuss this, but we may point out that the List presents 

 a number of extraordinary anomalies, for instance, the 

 Pied Wagtail is considered a species, whereas all the other 

 forms of the White Wagtail are considered as subspecies, 

 the Rock-Pipit and Water-Pipits are considered to be distinct 

 species, the British Willow-Tit and Northern Willow-Tit 

 are subspecies, and yet apparently the American Parus 

 atricapillus belongs to a different species, the Indian, African 

 and European Stonechats, though so much alike, are con- 

 sidered to be distinct species. 



There remain to be discussed species and subspecies 

 admitted by us and not to the B.O.U. List. The Committee 

 state that the Parrot -Crossbill only differs from the typical 

 form " in the enlarged size of its bill," and therefore they 

 consider it merely a variation or dimorphism. As a matter 

 of fact, the bird is larger in all its measurements and lays 

 larger eggs, and is only found in part of the range of the 

 Common Crossbill. The Committee are clearly in error on 

 this point and we fancy that few will agree with them. 

 Parus cristatus mitratus is omitted altogether, and the 



