LARID.E — STERNIN^ : TERNS, SEA SWALLOWS. 1011 



almost to ends of inner secondaries, but ending abruptly on rump, the upper tail-coverts 

 being pure white. Under parts considerably lighter than the mantle. On the throat, toward 

 chin and along borders of the black cap, this color fades into nearly or quite pure white, as 

 it does also on lower tail-eovei'ts ; under surface of wings and axillary feathers pure white. 

 Shafts of all the primaries white, deepening into blackisli toward their tips. Outer web of 

 1st primary black, with scarcely any hoariness. First 4 or 5 primaries grayish-black, strongly 

 silvered; their inner webs with a space of white along their inner margins. Tliis space on 

 the 1st primary at base occupies the whole web. becomes narrower as it ascends, and ends, 

 or becomes a mere line, about 1.00 from the tip; on other primaries it is of less extent, and 

 runs up along the centre of the web a little farther than on the edge ; on the innermost pri- 

 maries it is very narrow, but forms an entire margin to the inner webs, running to their tips. 

 The inner primaries have scarcely any grayish-black, being mostly of the color of the mantle. 

 Secondaries mostly pure white, but toward their ends grayish-bine to about equal extent on 

 both webs. Tail moderately forked, contained about If times in length of wnng; the folded 

 wings reacli 1.00-2.00 beyond it; middle feathers broad to their rounded tips; lateral ones 

 successively narrower and more " streaming," their outer webs light pearl-gray (lilce the back), 

 their inner webs nearly pure wliite. The outer pair, however, are grayish-blue on most of 

 their inner webs, especially terminally, while their outer webs are grayish-black. Feet light 

 coral-red. Adults in winter: As above, but cap imperfect, marked with white on front and 

 crown; under parts less pearly or quite w^iite; bill and feet dull. There is much less de- 

 cided difference in seasonal plumage of this s})ecies, forsteri, and others of the same subgenus, 

 than tliere is in the large Terns of the section Actochelidon, the pure black cap being worn 

 htuger. Length (average) 14.50; extent 31.00; wing 10.50; tail G.OO, forked 3.50; bill along 

 culmen 1.35; height at base 0.33; from feathers ou side of lower mandible to tip 1.60; gonys 

 0.80; gape 2.10; tibije bare 0.50 ; tarsus 0.80-0.85; middle toe 0.75, its claw 0.30; outer 0.70, 

 its claw 0.18; inner 0.48, its claw 0.14; hallux with its claw 0.28; whole foot about 1.75. 

 Extremes: Length 13.00-1(5.00; extent 29.00-32.00; wing 9.75-11.75; tail 5.00-7.00; tarsus 

 0.(56-0.87; bill 1.25-1.50; 9 averages a little less than ^. Young fall under tlie above 

 minima: length down to 12.00, wing to 9.00, tail to 4.00, bill to 1.J2, etc. Young-of-the- 

 year in August : Upper mandible brown, becoming blackish on culmen toward tip, and some- 

 what tiesh-colored basally along tomia; under mandible light yellow, darkening into brown 

 toward tip. Mouth yellow ; feet dull yellow, with scarcely a tinge of reddish. Forehead 

 grayish-white; on crown mixed with large, illy-defined blackish spots; on occiput and nape 

 black prcvailiuir, the extreme tips of the feathers only being gray; on sides of head, as far as 

 eyes, tlie black also nearly pure. Ground-color of upper parts a rather lighter shade of the 

 l)earl-blue of the adults, but every feather is tipped with dull light gray, and has a subter- 

 minal spot (generally a crescent or .semicircle) of light brown. These conspicuous spots and 

 tijis usually give the predominating color to the upper parts ; but are neither so distinct nor 

 so dark as in panidisea. Lesser wing-coverts brownish-black, forming a continuous band. 

 Lesser and median coverts conspicuously tip])ed with yellowish-gray; inner secondaries nearly 

 pure white at tlirir tip.s: other secondaries white, with the outer web, except at tip, and the 

 median portion of the inner web, dark ))lumbeous or ashy-gray. Primaries colored almost 

 exactly as in the adults. Rump white, with a tinge of pearl-blue. Tail forked 1.00 or a 

 little more; inner webs of all the rectrices nearly pure white, but outer webs plumbeous- 

 gray, increasing in intensity from within outward, so that the outer pair, which are but little 

 elongated, have their outer webs grayish-black, deepest toward their tips. Entin> under 

 ])arts, including under wing-coverts, pure white, with no trace of the pearly wash of the 

 adults. Nestlings grayish-buff (tf variable shade, mottled with <lusky on the upper parts, white 

 below, with dusky throat and |)ale buff sides; feet yellow. Eggs 2-3, rarely 4, 1.5.5-1.65 X 

 1 20-1.25, huff or pal(( brown with variable olivaceous shade, fully spotted with dark brown or 



