Carriker : List of the Birds of Costa Rica. 471 



U. S. Nat. Museum: Guayabo, March (Ridgway and Zeledon). 

 Bangs Collection : San Jose, San Pedro, Tenorio, Bolson (Under- 

 wood). 

 Carnegie Museum : Guapiles, March 24 ; Guacimo, Oct. 26 ; El 

 Hogar, Dec. 6 (Carriker). Six skins. 



The exact status of the Sparrow Hawk of Costa Rica has been 

 rather puzzling, but owing to the large series of specimens I have been 

 able to examine not only of birds from Costa Rica and Chiriqui, but 

 from Mexico and the southwestern United States, the true state of affairs 

 becomes evident. It is a well known fact that the Sparrow Hawk is 

 only a migrant in Costa Rica, reaching its greatest abundance there 

 during the months of November, December, and January ; and hence, 

 having only winter birds for study, they present more than the usual 

 difficulties experienced in determining birds in winter plumage, as 

 anyone who has worked with them knows. There can be no doubt, 

 however, that they are identical with the birds which breed in Mexico 

 and the southwestern portion of the United States, and which were 

 described by Lesson under the name of Tinnunculus phalama. Whether 

 this form is a good subspecies of the bird breeding in the eastern United 

 States is another question, and one not easily decided. There are 

 occasional birds from Costa Rica or Mexico as dark on the upper 

 parts, especially on the crown, as any breeding bird from Massachu- 

 setts, and there may also though rarely be found an eastern bird almost 

 as pale as those from the west. However, in a case such as that under 

 discussion, where the species has such a tremendous variation both in 

 size and coloration, even from the same locality, such extreme birds 

 are rather to be expected and can be accounted for under the 

 hypothesis of individual variation carried to an extreme. The 

 validity of this race does not depend upon such a point, but on the 

 question as to whether a series of breeding birds from the two regions 

 will bear out the differences in a constant manner, which they cer- 

 tainly do in this case. I would say that while the western bird is not 

 a very marked race, it is in my opinion a valid one, and the birds 

 from Costa Rica .are very probably a portion of those which breed in 

 Mexico, drifting southward during the winter to better feeding- 

 grounds. 



