AVES FALCONIDyB. 633 



Neck : Bluish lead-color, whitening on the throat and chin. 



Back : Interscapular region and lower back darker bluish lead-color ; the 

 rump shading to white and the upper tail-coverts pure white; both regions 

 crossed with narrow bars of slaty grey and the rump sometimes mottled 

 with that shade. 



Tail : White of the purest tone ; crossed by eight or more wavering, 

 narrow, slaty grey bars and by a broad sub-terminal band of slaty blue* 

 black, terminating in a band a third as wide as the last, pure white. 



Wings : Primaries blackish, the external exposed surfaces frosted with 

 silvery slate ; white at base of inner web, with markings and bars of bluish 

 sl.ite ; the secondaries bluish lead-color like the back, and tipped faintly 

 with silvery grey, almost white ; all the upper wing-coverts darker bluish 

 lead-color like the interscapular region ; lower wing-coverts and axillaries 

 lighter slate. 



Lower parts: Bluish lead-color; pale on the throat and chin, darkest on 

 the chest and breast and again light about the abdomen in the region of 

 the vent ; the lower tail-coverts white, pure in tone, with some mottlings 

 and many narrow, wavering bars of pale grey slate ; the thighs light slate, 

 barred finely with a darker shade. 



There appear to be no field notes available to indicate the color of the 

 bill, the cere, the irides, or feet and legs, as they look in life. 



The female adult does not differ from the male in appearance, but is a 

 little larger; length 23.50; wing 17.00; tail 10.00 inches. 



No immature birds or young of the year have been available for study 

 and description. 



Geographical Range. Southern Patagonia, the Straits of Magellan 

 region, the whole of Tierra del Fuego and the Falkland Islands. 



This is one of the rarer birds of prey even in the region where it occurs 

 and there are but few specimens, probably less than thirty all told, in the 

 great museums of the world, and recent accounts of the life history of 

 this hawk are entirely lacking. It was not encountered by the naturalists 

 sent out by Princeton to Patagonia. That it is a close ally of Buteo 

 erythronotus is apparent and it is not impossible that future study may 

 show relationships which will prove the specific identity of the two 

 forms. 



