108 
webs of primaries marked with transverse spots of white. Rest of plum 
age continuous plumbeous, inclining to pearl-gray or ashy-blue on the 
lower surface (where the shafts of the feathers are usually conspicuously 
darker), and on the upper parts becoming gradually lighter toward the 
nape, which is bluish-plumbeous, abruptly contrasted with the black of 
the pileum. 
Young :—Pileum brownish-black, bordered below by a continuous 
nuchal collar of unvariegated ochraceous. Rest of upper parts plain 
blackish-sepia, unbroken by any exposed white markings, and scarcely 
relieved by the narrow faint tips of fulvous to some of the feathers. 
Tail black, narrowly tipped with white, and crossed by four to five nar¬ 
row bands of grayish-brown or mixed brown and white; these bands 
more regular, continuous, and almost entirely white on the under surface. 
Lower parts entirely ochraceous or white, paler on the crissum, and 
without any markings, except an occasional dusky shaft-streak here 
and there. Auriculars black. 
Sexes alike in colors, but differing in size, as follows:— 
Male: —Wing, 8.00-8.50; tail, 7.20-8.00; culinen, 0.55-0.00 ; tarsus, 
2.25-2.40; middle toe, 1.45-1.50. (Six specimens.) 
Female: —Wing, 9.50-10.00; tail, 8.00-8.80; culinen, 0.70-0.75; tar¬ 
sus, 2.45-2.70; middle toe, 1.00-1.80. (Five specimens.) 
The principal variations noticed among the few adults before us are 
quite trifling. The white of the lining of the wing and of the crissum 
is usually much clouded by a fine, irregular mottling of plumbeous; 
but in Flo. 01,303, S , from Yeragua, there is none of this mottling, 
while the shafts of the feathers are conspicuously black. In Ho. 10,573, 
Panama (Frijole), the usual blackish shaft streaks of the lower parts 
are almost obsolete. The plumbeous of the nape is also darker or 
lighter in different individuals, producing thereby a variable abruptness 
of contrast with the black of the pileum. The young plumage varies 
more. Some are nearly pure white beneath, but a light ochraceous 
shade is the more usual color of the lower parts. In a young male, 
however (43,047), from Costa Rica, the entire lower parts and the 
nuchal collar are deep tawny-ochraceous, almost rufous on the breast 
and thighs. A young female from Costa Rica (Ho. 39,733) is strikingly 
similar in all the details of coloration to the adult of Micrastur melano- 
leucus , even to the markings of the tail. The general form and the size, 
also, are so similar to the adult male of that bird that the generic 
characters only are different. 
List of specimens in United Stales National Museum. 
1 
Catalogue Xu. j 
Original Xo. 
1> 
a, 
x . 
Vt p 
L £ 
ft 
Sex and age. 
Locality. 
W li c n col¬ 
lect cd. 
From whom received. 
% 
16573 
s. 
cf ad. 
Panama Railroad- 
McL. 
35182 
s. 
? 
S.-ui Jos6, Costa Rica.. 
Sept. 4,1864 
Carmiol ... 
3973.1 
166 
M. 
Qjiiv. 
Costa Rica . 
Nov. —, 1863 
A. von Frantsjius ... 
430-17 
17 
M 
cf.juv. 
Costa Rica (Turrialba) 
July 17, 1866 
J. Cooper. 
47363 
62127 
66333 
3704 
11 
M. 
S. 
s. 
cf ad. 
cf ad. 
rfjnv. 
Costa Rica. 
Lipurio, Costa Rica ... 
July 30,1866 
Carmiol. 
W. M. Gabb. 
67868 
s. 
? ad. 
.do. - 
.* * ' * 
_do. 
Othir specimens examined— Mus. Fliilu, Acad., 5; Boston Soc., 2; G. N. Lawrence, 5; 
American Mus., N. i., 1. total, 21. 
