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NORTH AMERICAN BIRDS. 
Subgenus NIBUS, Cuvier. (Page 124.) 
Common Characters. Adult. Above bluish slate-color ; the tail with obscure 
bands of darker, and narrowly tipped with white. Beneath transversely barred 
with white and pinkish-rufous ; the anal region and crissum immaculate white. 
Young. Above grayish umber-brown, the feathers bordered more or less dis- 
tinctly with rusty ; scapulars with large white spots, mostly concealed ; tail- 
bands more distinct than in the adult. Beneath white, longitudinally striped 
with dusky-brown. 
1. N. fuscus. Middle toe shorter than the bare portion of the tarsus, in 
front ; tarsal scutellae fused into a continuous plate in the adult male. Tail 
nearly even. Top of head concolor with the back ; tail merely fading into 
whitish at the tip. Concealed white spots of the scapulars very large and 
conspicuous. Wing, 6.45 - 8.80 ; tail, 5.70 - 8.20 ; culmen, .40 - .60 ; tarsus, 
1.85-2.25; middle toe, 1.10-1.55. Eggs white, strongly blotched with 
brown. Hob. Whole of North America and Mexico. ( Sharp-shinned 
Hawk.) 
2. N. cooperi. Middle toe longer than the bare portion of the tarsus, in 
front ; tarsal scutellse never fused. Tail much rounded. Top of the head 
much darker than the back ; tail distinctly tipped with white ; concealed 
white spots of the scapulars very small, or obsolete. Eggs generally dull 
bluish-white, very rarely more or less obsoletely blotched with yellowish- 
brown. Wing, 8.50-11.00; tail, 7.50-10.50; culmen, .60 -.80; tarsus, 
2.10-2.75; middle toe, 1.30-1.85. 
Adult. Rufous markings beneath, in form of detached bars, not ex- $ 
ceeding the white ones in width ; dark slate of the pileum and nape 
abruptly contrasted with the bluish-plumbeous of the back ; upper tail- 
coverts narrowly tipped with white ; scapulars with concealed spots of 
white. Young. White beneath pure ; tibiae with narrow longitudinal 
spots of brown. Wing, 9.00 - 11.00 ; tail, 8.00-9.80; culmen, .65- 
.80; tarsus, 2.45-2.75 ; middle toe, 1.55- 1.85. Hab. Eastern region 
of North America. (Cooper's Hawk) var. cooperi. 
Adidt. Rufous markings beneath, in form of broader bars, connected 
along the shaft, almost uniform on the breast ; black of the pileum and 
nape fading gradually into the dusky plumbeous of the back; upper 
tail-coverts not tipped with white, and scapulars without concealed 
spots of the same. Young. White beneath strongly tinged with ochra- 
ceous; tibiae with broad transverse spots of brown. Wing, 8.50-10.60 ; 
tail, 7.50- 10.50; culmen, .60 -.75; tarsus, 2.10-2.75; middle toe, 
1.30-1.75. Hab. Western region of North America, Mexico. (Blue- 
backed Hawk.) . . . . . * . var. mexicanus. 
™ Subgenus ASTUR, Lacepede. (Page 125.) 
A. palumbarius. Adult. Above, continuously uniform bluish slate-color ; 
the tail with several more or less distinct broad bands of darker, and 
narrowly tipped with white. Top of the head blackish ; a streaked whitish 
superciliary stripe. Young. Above much variegated with brown and pale 
ochraceous ; bands on the tail more sharply defined. Beneath pale ochra- 
ceous, with longitudinal stripes of dark brown. . 
