AVES FALCONID^. 64 7 



The variation in plumage in this hawk has long been known and has 

 been dwelt on by those who have observed the birds. There has been, 

 so far as we can discover, no detailed account of the dark phase discussed 

 in this connection from material taken by Mr. Hatcher. There is in the 

 Princeton Museum a bird (No. 8671) that nearly approaches No. 7865, 

 from the Cordilleras of Patagonia. It was collected by S. Pozzi, in the 

 La Plata region near Buenos Aires, and is labelled Buteo albicaudatus, 9, 

 needless to say an error in identification. While the bird is not so defi- 

 nitely dark on the lower surface, the black of the throat and breast shading 

 into white about the vent, yet the upper parts are dull deep brownish-black 

 throughout. The tail is much as in the dark bird already described. 



All the birds here considered have been carefully compared with the 

 material in the British Museum and the descriptions are wholly based on 

 birds procured by the naturalists sent out by Princeton, who were fortunate 

 enough to obtain material extending our knowledge of the appearance 

 of this hawk, as well as to get all the heretofore known plumages. 



A. H. Holland, in his account of the Birds of Estancia Sta. Elena (Ibis, 

 p. 216, 1895) says of this species: "A common hawk here at all seasons^ 

 often seen in company with C. cinereus, and beating up its prey from 

 bushes and weeds in much the same way. Its stoop is more powerful, 

 and its longer breadth of wing enables it to fly with more despatch and in 

 a sailing manner. It breeds in the long grass, but, so far, I have not dis- 

 covered its nest." 



Hudson in "Idle Days in Patagonia," 1893, pp. 212-214, describes its 

 habitat as follows: "On arriving at a hill, I would slowly ride to its sum- 

 mit, and stand there to survey the prospect. On every side it stretched 

 away in great undulations; but the undulations were wild and irregular; 

 the hills were rounded and cone-shaped, they were solitary and in groups 

 and ranges; some sloped gently, others were ridge-like and stretched 

 away in league-long terraces, with other terraces beyond ; and all alike 

 were clothed in the grey everlasting thorny vegetation. How grey it all 

 was ! hardly less so near at hand than on the haze-wrapped horizon, where 

 the hills were dim and the outline blurred by distance. Sometimes I 

 would see the large eagle-like white-breasted buzzard, Buteo erythronotus, 

 perched on the summit of a bush half a mile away; and so long as it 

 would continue stationed motionless before me my eyes would remain 

 involuntarily fixed on it, just as one keeps his eyes on a bright light shining 

 in the gloom ; for the whiteness of the hawk seemed to exercise a fasci- 



