ElDGWAY on the Plumage of Gyrfalcons. 93 



detailed description of the perfect adult dress of this dark form of 

 the Gyrfalcon has, to my knowledge, been published. 



Adult ^. — Above continuous plumbeous-slate, interrupted by a some- 

 what V-shaped patch of pale buff, or buffy white, longitudinal markings 

 on the nape ; the head perfectly uniform, the feathers of the dorsal-region 

 and wings showing paler borders and transverse spots, there being about 

 one pair (one on each web) of the latter on the exposed portion of each 

 feather; remiges and primary coverts plumbeous-slate, without any spots, 

 but with paler edges. Rump and upper tail-coverts more bluish than the 

 back, and with distinct transverse spots and bars of light bluish-plumbeous, 

 these bars regular and sharply defined on the upper tail-coverts, where 

 they average, like the darker ones, about .25 of an inch in width; the 

 shafts of these feathers conspicuously darker than the ground-color. Tail 

 similar in colors and markings to the upper coverts, there -being about 

 eight or nine bands on that portion of the tail not concealed by the coverts ; 

 the light bars more or less mottled, finely, with darker ; tip of the tail, 

 rather narroAvly, whitish. Ground-color of the lower parts creamy white, 

 or pale cream-color, changing to light plumbeous on the thighs and anal 

 region, the crissum tinged with the same. Chin and throat washed with 

 grayish, and streaked (not sharply) with dusky; whole jugulum and breast 

 thickly marked with sharply defined longitudinal stripes of blackish slate, 

 these markings gradually assuming on the abdomen the form of tear- 

 shaped and oval spots; flanks with wide transverse spots of blackish slate, 

 some of the spots more or less cordate ; tibial plumes thickly barred with 

 transverse, somewhat cordate spots of deep plumbeous, the shafts con- 

 spicuously blackish ; anal region similarly but more densely marked ; 

 lower tail-coverts very regularly barred with deep plumbeous, the bars 

 sharply defined, somewhat crescentic, and about .30 of an inch in width, 

 or a little narrower than the lighter ones. Lining of the wing irregularly 

 spotted with dark slate and pale cream-color, in nearly equal proportion ; 

 under surface of the quills silvery plumbeous, faintly and irregularly mot- 

 tled with pale creamy, but not showing any tendency to form transverse 

 or ovate spots. Wing, 14.00'- 14.40 ; tail, 8.40-9.00 ; cuimen, .90 ; tarsus, 

 2.25-2.35 (bare portion about .80) ; middle toe, 1.90. 



Adidt 9 • — Much darker than the ^, and of a more sooty shade. No 

 trace of the light nuchal markings ; spots of the back, etc., smaller and 

 more scattered ; rump and upper tail-coverts slaty-plumbeous (about like 

 the back of the ^), the former with small scattered spots, the latter with 

 narrow bars of light grayish or dirty whitish. Tail brownish slate, nar- 

 rowly tipped with whitish, and marked with incomplete or interrupted 

 narrow bands of light mottled grayish ; none of these bars, except the 

 subterminal ones, reach the shaft ; they are narrower and wider apart than 

 those of the ^, about eight showing beyond the upper coverts on the 

 middle rectrices. Chin and throat as in the $, but remaining lower 



