210 



dark slate, barred with greyish white in Northern 



oldest dress ; browner, less slaty, in less United States. ^ 



mature birds (this phase much resembhng 



plumage of islandus). Immature : bill 



bluish black ; first plumage plain brown 



above ; below heavily striped lengthwise 



with dark brown ; tail brown with faint or 



incomplete paler bars ; later whitish 



spots and bars appear on upper parts, the 



pale tail bars widen, and the large wide 



stripes on under parts decrease into streaks 



and into bars on the flanks. [Melanistic 



phase {obsoletus)] : this, common in 



Labrador, is nearly uniform brownish 



black instead of white ; below marked 



with white streaks or spots, diminishing 



according to age in the same way as the 



dark markings diminish in the white phase. 



Gen. XCV. RHYNCHOFALCO Ridgw. (1873). 

 Type by orig. desig. F . femoralis Temm. = F . fusco-ccBrulescens Vieill. 



Wing with third primary longest ; first shorter 

 than second ; tarsus longer than middle toe, with 

 transverse scutes ; sexes alike ; size moderate. 



*311. RhyncJwfalco fusco-ccsrtdescens fusco-cceru- Argentina; 



lescens Vieill., X. Diet., xi., p. 90 (1817). Patagonia and 



[ex Azara — Paraguay.] Tierra del Fuego 



Aplomado Falcon. (migratory). 



Wing S 245-260, ? 277-280 mm. ; ^ above 

 dull slaty, greyer on crown and lighter on 

 rump ; upper tail-coverts barred and tipped 

 with wiiitish ; tail blackish brown, with 



^ All the winter birds I examined in the American museums from Canada and 

 E. and N. United States were of this form ; a few in the white plumage, the rest in 

 the brown immature plumage, but none in the grey adult " primitive " phase. 

 Of course, those from the West, British Columbia, etc., are generally alascanus, 

 which appears to migrate down the coast in winter. They are determinable by 

 their small size and dark adult plumage. 



