ANATID.E THE SWANS, GEESE, AND DUCKS, 169 



SP. CHAK. Adult male: Head and upper half of the neck glossy blue-black, with re- 

 flections of green, blue, and violet, according to the light; a somewhat wedge-shaped ver- 

 tical patch of white across the anterior half of the lores, bordering the lateral base of the 

 bill, the upper part forming an acute angle on each side of the forehead, the lower part 

 rounded. Upper parts velvety black, with a soft bluish violet tinge ; outer row of scapulars 

 marked with a mesial cuneate stripe of satiny white, the greater portion of the stripes con- 

 cealed, so that the exposed portion forms roundish or oblong spots; middle wing-coverts 

 white, producing a broad bar; exposed terminal half of greater coverts, with the whole of 

 the exposed portion of tlie five or six inner secondaries, white, forming a large, somewhat 

 cuneate, patch. Outer feathers of the sides and flanks widely edged exteriorly with deep 

 black; femoral region and sides of crissum dull black. Lower half of neck (all round) and 

 entire lower parts (except as described) pure white. Bill black (in skin) ; iris bright yellow; 

 legs and feet pale. Adult female: Head and upper half of the neck dark sepia-brown, 

 considerably darker and somewhat more purplish than in the female G. clangula ameri- 

 cana; lower part of the neck, all round, white, sometimes tinged with gray on the nape. 

 Upper parts dark grayish brown, the scapulars, interscapulars, and smaller wing-coverts 

 tipped with lighter ash-gray; last two or three rows of middle wing-coverts tipped with 

 white, forming a broken, rather narrow, transverse patch ; greater coverts with the ter- 

 minal half of their exposed portion white, as in the male, but distinctly tippped with black- 

 ish, forming a conspicuous dusky bar between the white of the coverts and that of the in- 

 ner secondaries. Chest and sides a=>h-gray, the feathers darker and more uniform, the 

 flanks darker; other lower parts pure white. Bill usually parti-colored (black and yellow), 

 but sometimes wholly black. 



Adult male: Wing, 9.00-9.40 inches: culmen, 1.65-1.80; depth ol bill at base, 95-1.10, width, 

 .75-. 85; tarsus, 1.50-1.60; middle toe, 2.45-2.50. Adult female: Wing, 8.25-8.75 inches: cul- 

 men, 1.40-1.60; depth of bill, .85- -.90; width, .70; tarsus, 1.30-1.60; middle toe, 2.15-2.20. 



Bearing; in mind the salient points of difference, as given above 

 and on page 166, there need be no difficulty in distinguishing the 

 adult male of this very distinct species from that of the com- 

 m^n Golden-eye. With the female, however, the case is very dif- 

 ferent ; the two species being so much alike that, with the series 

 at our command (about twenty specimens, including six un- 

 questionably referable to G. islandica] , we must acknowledge 

 our inability to give infallible points of distinction. The ex_ 

 amples which are known to represent G. islandica differ from 

 the positively determined females of G. clangula americana in 

 the following respects: (1) The color of the head and upper 

 half of the neck is considerably darker, being a rich sepia- or 

 snuff-brown, rather than grayish brown; (2) the greater wing- 

 coverts are distinctly tipped with black, forming a conspicuous 

 dusky stripe between the two larger white areas of the wing, 

 which in G. clangula americana are (usually, at least) merged 

 into one continuous space. Further than these we find no dis- 

 tinction, while indeed some examples are so decidedly inter- 

 mediate in both respects as to render it quite uncertain to 



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