148 LIST OF DIXTRNAL BIRDS OF PREY. 



APPENDIX I. 



On Urubitinga zonura and Urubitinga ridgwayi. 



Mr. RidgwaYj in the article in his ' Studies of American 

 Falconidse' relating to Urubitinga zonura, remarks: — ''The 

 South-American and Middle-American specimens of this 

 species are so easily distinguished that they seem to be 

 separable as well-marked geographical races " ; and he adds 

 a summary of the diflferences which he has observed between 

 the two races. Some of these do not appear to me to be 

 sufficiently constant and distinct to be much relied on ; but 

 the following, which I have noted on a comparison of eight 

 adult or nearly adult specimens of the southern with eight 

 of the northern race, may, I think, be accepted as a sufficient 

 justification for regarding the latter, which inhabits Mexico 

 and Guatemala, as a subspecies distinct from the southern 

 U. zonura, the range of which extends from Costa Rica 

 southward, to Chili. I propose, as the difference between 

 the two races was first pointed out by Mr. Ridgway, to 

 indicate that circumstance by attaching to the more r.orthern 

 of the two the subspecific designation " ridgivayi ;" and I 

 think that U. ridgwayi may be defined as distinguishable 

 fi'om U. zonura, when fully adult, by the greater proportion 

 of white mingled with the black plumage of the under wing- 

 coverts and of the tibiae, and by the larger number of alter- 

 nate black and white cross bars on the tail, as also by the 

 comparative average narrowness of the white bar immediately 

 above the subterminal black bar on the tail. 



The following particulars of the specimens which I have 

 examined, and which are contained in the Norwich Museum 

 and in the collection of Messrs. Salvin and Godman, may 

 serve to exhibit more clearly the peculiarities of the two 

 races when adult (in their immature plumage they do not 

 seem to me to be distinguishable). It will be seen that the 



