674 STERNA CANTIACA, SANDWICH TERN. 



lower iriamlible, 1 ; gonys, 1.20 (longer than rami) ; tarsus, 1 ; middle toe and claw, 

 very slightly longer. 



Adult, ivlnier plumage. — The yellow tip of the bill decreases in extent and intensity 

 of color ; the front is white, either pure or speckled with black ; the crown variegated 

 with black and white, the fornjer color consisting of small, narrow, distinct streaks 

 along the shaft of each feather ; but the long occipital crest, which does not entirely 

 disappear at this season, usually remains of an unmixed brownish-black. The lateral 

 tail feathers are shorter than in snnnuer. 



Youny-of-the-ymr in August. — Considerably smaller than the adult, as is usual in 

 this subfamily, the wing being a full half inch shorter. The bill is shorter and weaker, 

 and is without any very sharply-defined angles and ridges. It is brownish-black, the 

 extreme point only yellowish. The crown, tront, and occiput, are biownish-black, va- 

 riegated with white ; the white touches very small on the forehead. The upj)er parts 

 are as in the adult, but everywhere marked with irregularly-shaped but well-defined 

 spots and transverse bars of decided brownish-black. There is no well-formed occip- 

 ital crest until after the first moult. The primaries ore like those of the adults. The 

 tail, however, is very different. The feathers for three-fourths their length are of the 

 color of the back ; this color gradually deepens, until toward the tips it becomes 

 brownish-black, each feather having a terminal irregular edge left whitish. The tail, 

 in shape, is simplj' deeijly emarginate, the outer feathers being but slightly longer than 

 the second. 



OtJtcr variations. — The yellow tip of the bill varies greatly in extent, and has also a 

 varying outline and distinctness of definition from the black. The length of this yel- 

 low tip appears to depend in a good measure upon the age of the bird, while the 

 intensity of the color is apparently affected most by the season of the year. The dif- 

 ference between the longest and shortest tips that have come under my observation is 

 full half an inch (varying from i to f). The length of the tarsus and toes seems very 

 constant, as are the markings of the primaries in their extent and distribution. The 

 difference in length of wing from the carpus is only about one-half an inch in adult 

 birrls. The forking of the tail varies somewhat, but never equals that of the species 

 of Sterna proper. 



A series of winter skins from Jamaica in, probably, their first moult (if they really 

 belong to this species), dilfer from adult examples I'rom various points on the Atlantic 

 doast in being every way considerably smaller. The bills are about a third of an inch 

 shorter than the average ; and other parts diifer proportionally. 



European : White margin of inner web of outer three or four primaries wide, ex- 

 tending quite to tip, which it wholly occupies. Breadth of white portion one and a 

 half inches from tip of first primary, 0.25 of an inch. 



American : White margin of inner web of three or four outer primaries narrow, 

 falling short of tip, which is wholly occupied by the black portion. Breadth of white 

 margin one and a half inch from tiji of first primary, U.IO of an inch. 



The foregoing exi)resses certain points of difference I have found to subsist between 

 the American and European birds, but I do not now attach to them anj' imiiortance, 

 since they may depend mainly upon age of the individual quills. Whether or not 1 

 can agree with my friends. Dr. Sclater and Mr. Salvin, "that Dr. Coues has ably dis- 

 cussed the subject," I am read}' to concede that he "has succeeded in reducing the 

 differences to a minimum which is too small to warrant specific separation !" 



Subgenus Sterna, Linn. 



< sterna, Linn., Syst. Nat. 1748, et auct. (Type S. hirundo, Linn.) 



> Thahissea, Kaup, Sk. Ent. Eur. Thierw. 1829, 97. (Type S. paradisea, Brunn.) 



> Hijdrocccropis, BoiE, Isis, 1844, 178. (Same typo.) 



'^ Stcrnula^ BoiE, Isis, 1822, 5G3. (Type S. minuta, Linn.) 



Gen. char. Bill about as long as, or a little shorter than, the head, much longer than 

 the tarsus; variable in stoutness, but gen rally quite slender, compressed, very acute; 

 the culmen declinato-couvex, gradually and regularly curved from base to apex ; the 

 commissure gently curved ; the outline of the rami straight, or a little concave ; the 

 gonys quite straight, slightly ascending; the eiiiinentia symphysis well marked, but 

 not very prominent. Wings long and pointed, typical of the subfamily. Tail long, 

 forked ; varying in these resi)ects; but the lateral feathers always elongated, tapering, 

 and filamentous, and the depth of the forfication very considerable. Tarsus slender, 

 comi)ressed, a little shorter than the middle toe and claw, slightly longer than the 

 middle toe alone, much shorter than the l)ill, about as long as the ramus of the inferior 

 maxilla. Toes moderately long. Webs moderately broad and incised ; varying in this 

 respect, but never so deeply cut out as in Hi/drovlulidon. Size moderate, or very small ; 

 general form slender and graceful. Head without a decided occipital crest. A black 

 pileum ; the back some shade of blue ; the primaries variegated with black and white, 

 and silvery ; the under parts white, with or without a plumbeous or rosy tinge. 



