G70 STERNA REGIA, ROYAL TERN. 



The glossy greenish-black pilenm does not extend below the eyes, and is so narrow 

 on the sides of the ujjper mandible that it allows a broad white streak to extend along 

 the edge of tlie mandible to the extreme tip of the feathers. The mantle is exceed- 

 ingly light pearl-blue, lading imperceptibly into white on the rump and toward the 

 extremities of the tertials. The tail is white, with a faint tinge of pearly, especially 

 on the central feathers and inner webs of the others. The secondaries are pure white 

 for Mieir Vvhole length, except a small space on the outer web near the tip, which is 

 grayish-blue, deeper than the mantle. The outer web of the first primary is grayish- 

 black ; the inner web of the same has a space of black extending the whole length of 

 the feather, Aery narrow at the base, widening as it runs toward the tiji, within li 

 inches of which it occupies the whole web, to the exclusion of the white portion ; the 

 rest of the web is white, separated from the black by a straight distinctly-defined 

 trenchant line of division. The second, third, fourth, and fifth primaries have the same 

 general characteristics, but the white space rapidly grows narrower and shorter, and 

 runs up further in the centre than along the edge of the web, so that for a little way 

 from its end it has a border of blackish along its outer margin. The other primaries 

 have no grayish-black, but are wholly pearl-blue, their inner webs margined with 

 white. The bill is coral or orange-red, with a slightly lighter tip. The feet are black- 

 ish, their soles dull yellowish. 



Winter plumage. — Bill less brightly colored than in summer, its apex and tomia dull 

 yellowish. Front white ; crown variegated with black and white, the former color in- 

 creasing on the occiput and nuchal ciest, which latter, though shorter than in summer, 

 is almost or quite unmixed with white. This black extends forward on the sides of 

 the head to the eye, which it includes. The tail is not pure white, as in summer, but 

 is glossed over with the bluish of the mantle, which deepens toward the tips of the 

 feathers into dusky xilunibcous. It is also considerably less deeply forked, the lateral 

 feathers having little or nothing of a filamentous character. Otherwise as in summer. 



Young-of-thc-yeur in August. — Bill considerably smaller and shorter than in the adult ; 

 its tip less acute, and its angles and ridges less sharply defined ; mostly reddish-yellow, 

 but light yellowish at tip. Crown much as in the adults iu winter, but the occipital 

 crest scarcely recognizable as such. Upper parts mostly white ; but the pearl-gray of 

 the adults appearing in irregular patches, and the whole back marked with small, 

 irregularly shaped, but well-defined spots of brown. On the tertials the brown occu- 

 pies nearly the whole of each feather, a narrow edge only remaining white. Lesser 

 wing-coverts dusky plumbeous. Primaries much as in the adults, but the line of de- 

 marcation of the black and white wanting sharpness of definition. Tail basally white, 

 but soon becoming jdumbeous, then decidedly brownish, the extreme tips of the feath- 

 ers again markedly white. Otherwise as in the adults. 



Dimensions of the adults. — Length, 18 to 20 inches ; extent of wings, 42 to 44 ; wing, 

 from carpal joint, 14 to ir> ; tail, C to 8 ; the depth of forking, about 3 to 4 ; bill, along 

 culmen, 2..50 to 2.7D ; along commissure, 3.75 ; its height at base, 0.70 ; its width, 0.50 ; 

 gonys, 1 to 1.2.5 ; tibiae base, 0.90 ; tarsus, 1.37 ; middle toe and claw, 1.40.* 



Other variations.— For so large a species, and one of this family, the variations are not 

 very great. When found, they consist chiefly in difterences of dimensions, as usual, 

 aT d iu a less degree in the shape and size of the bill. The measurements indicated 

 above are, I believe, about the average. There seems to be no diti'erence in the sexes. 

 The young are invariably smaller, with weaker bill and feet, and only slightly forked 

 tail. The relative proportions of the tarsus and tail of the adults, as well as the ab- 

 solute length of these parts, seem to be very constant, and always preserve the radical 

 difference from those of elegans, which is noticed below. 



Immature birds, of course, exhibit every gradation between the state of plumage 

 above described, and that of the adults. When very young, however, they preserve 

 pretty constantly the pattern of coloration given. The adults, iu winter, vary a good 

 deal as to the exact amount of black remaining in the pileum ; tut the essential char- 

 actei's of white front, spotted vertex, nearly black occiput, and variegated lateral stripe 

 along the sides of the head, are always found. In the iilumage of adult summer birds 

 I have found no variations worth noticing. 



Comparison u:Uh allied species. — The species is liable to be confounded with oidy one 

 other of North America— (/rt/eriCHZ«/rt. While the bill is nearly or quite as long as is 

 that cf ai.spiiis, it is of a very different shape, being every way weake|-, with a straighter 

 culmen. Besides, the coloration of the primaries of casjnus is jieculiar in lackiAg the 

 white stripe on the inner webs of the primaries. S. galcriculata is more nearly allied ; 

 but it is considerably smaller, with the bill, though as long or nearly so, much slen- 

 derer and differently shaped (compare descriptions), with a different i>rt>portionate 

 length of tarsus and toes, a rich rosy blush iu the breeding season, «.tc. 



Bihliograpkij. — While I agree with Messrs. Sclater and Salvin that S. maxima Bodd. 

 (=caycnncusis Gni., cayana Lath.) is not improbably this .species, I cannot make the 

 identification satisfactorily. The description (of a young bird) is too short and vague 

 to be determined positively. It might have been based on Fhatusa magiiirostris. The 



* Audubon's measurements, " taisus, 3rj ; middle toe, 1 ; its claw, i ; " are so glariuglj' 

 erroneous, that they must be either typographical or clerical mistakes. 



