210 
dark slate, barred with greyish white in Northern 
oldest dress; browner, less slaty, in less United States.? . 
mature birds (this phase much resembling 
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-cerulescens Vieill. 
Wing with third primary longest ; first shorter 
than second ; tarsus longer than middle toe, with 
transverse scutes; sexes alike; size moderate. 
*311. Rhynchofalco fusco-cerulescens fusco-ceru- Argentina ; 
lescens Vieill., N. Dict., xi., p. 90 (1817). Patagonia and 
[ex Azara—Paraguay.]| Tierra del Fuego 
Aplomado Falcon. (migratory). 
Wing ¢ 245-260, 2 277-280 mm. ; 3g above 
dull slaty, greyer on crown and lighter on 
rump ; upper tail-coverts barred and tipped 
with whitish; tail blackish brown, with 
1 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. 
