fi68 STERNA CASPIA, CASPIAN TERN. 



fully as much as the latter surpasses the third. The tail is of peculiar shape ; it is 

 short, the eiiiar<^inatiou being ouly 1^ inches. The middle feathers are broad to their 

 very ends, which are rounded ; the lateral ones become successively more lengthened 

 and acute, till the external pair narrows rapidlj^ to a fine point ; but this pair has 

 nothing of the sleuder and filamentous character common to most of the species. 



The feet are short, and of moderate robustness. The tibite are bare for ouly about 

 f of an inch, or rather less than in regia, which is a much smaller bird. The tarsus is 

 peculiar in having the scutella on its anterior aspect replaced bj' polygonal plates of a 

 similar character to those of the lateral aspect, but larger, smoother, more regular. 

 The toes superiorly have something of this reticulation. The tarsus is elsewhere cov- 

 ered with small, rough, elevated plates of irregular shape, as is also the superior sur- 

 face of the webs. The middle toe is a little less than the tarsus ; the outer is nearly 

 as long, the tip of its claw reaching beyond the base of the middle claw ; the inner is 

 very short, its claw not reaching the base of the middle one. The hallux is extremely 

 abbreviated. The claws are all short, stout, little curved or acute. The iuterdigital 

 membranes are rather narrow and deeply incised, especially the inner one, the emargin- 

 ation of which reaches to between the second and third joints of the median digit. 



Bill dark vermilion red, growing lighter and somewhat "diaphanous" toward the 

 tip. Pileum and occipital crest glossy greenish-black, extending to below the lower 

 level of the eyes, and occupying the termination of the feathers on the side of the man- 

 dible to the exclusion of the white. The lower eyelid is white, forming a noticeable 

 spot on the greenish. A white streak along the sides of the upper mandible, )wf, how- 

 ever, extending to the end of the feathers. Mantle pearl-blue, the line of demarcation 

 between it and the white rather indefinite, both on the nape of the neck and on the 

 rump ; most of the tail feathers, and especially the central ones, retaining a more or 

 less notable pearly tint. The rhachidesof the primaries are yellowish-white; the pri- 

 maries themselves grayish-black, but when new, so heavily silvered over as to appear 

 of a light hoary gray, especially on their superior aspects. On the inner web of all 

 there is a central light field ; this is verj" narrow, even on the first primary, although 

 it runs for some considerable distance, and on the others it rapidly grows less ; and it 

 has no trenchant line of division on any of the primaries from the darker jjortions of 

 the feather. The whole inner web of the secondaries is pure white, the outer pearl- 

 blue. Legs and feet, with their soles, black. 



Adult, uinUr i)}mnage. — The winter plumage of this species, as is the case with other 

 Terns, is chiefly disticguished by a diminution in the brightness of the colors of the 

 bill, and by a change in the character of the pileum. The vermilion is replaced by 

 light orange-red, growing still yellower toward the tip of the bill and along the tomia. 

 The forehead is white, usually quite jiure ; the crown white, with small, narrow, dis- 

 tinct streaks of brownish-black along the shaft of each feather. On the sides of the 

 head, before and behind the eyes, and over the auriculars, the black is more largely 

 intermixed with the white ; and on the nape of the neck, that is toward the termina- 

 tion of the occipital crest, the black is the predominating color, being only slightly 

 variegated with white. There is no essential difference in the amount of emargination 

 of the tail, but it has ordinarily at this season more of a pearl-blue tinge than in 

 summer. 



Toitng-of-the-year. — Every way much smaller than the adult, the bill especially 

 smaller, shorter and weaker, and of a duller red, more inclining to orange. Upper 

 parts as in the adult, but the pearl-blue everywhere spotted with very numerous 

 rather small roundish or hastate spots of browni.sh-black, largest on the tertials. Fore- 

 head grayish-white; vertex speckled unto grayish-white and black, the latter color 

 increasing in amount until it becomes nearly or quite pure on the short occipital crest. 

 Wings much as in the adult. Tail much shorter and less forked ; the rectrices with 

 brownish spaces near their tips, chiefly on their inner wels. Under parts dull white. 

 Legs and feet rather shorter and weaker than those of the adult, but of much the same 

 color. 



A series of American skins, compared with a fully adult bird from Europe, differ in 

 size and proportion, as shown by the following table of comparative measurements : 



Comparatice measurements of American and European birds. 



Amer. Eur. 



Length of bill along culmen 2.75 2.40 



Length of bill along gaue 4.00 3.55 



Height of bill at base. r 0.90 0.75 



Width of bill opposite nostrils jO 0.50 



Length of w ing from flexure 1G.50 15.00 



Length of tarsus 1.75 1.65 



Length of middle toe and claw l.(>5 1.55 



Length of tail 5.75 5.25 



From these measurements it is apparent that the American bird is decidedly larger 

 than the European. The bill is neaily a third of au inch longer, and at the same time 



