NATURAL SCIENCES OP PHILADELPHIA. 5-15 



DiAG. — S. Sternx hirundini sirmWs : sed rostro longiore, valde robustiore, tarsis 

 longioribus, validioribus ; cauda ruagis product^, perlacea, rectrice lateral! 

 pogonio interno fusco-griseo, externo albo. 



Habitat. — Very extensively distributed over North America. Atlantic Coast 

 and Gulf of Mexico. Fur countries. Great Lakes and Rivers. Texas. Utah. 

 California. 



In vievr of the considerations presented in the two preceding articles, it may 

 be well to look somewhat carefully into the characters of the present species. 



Adult, spring plumage. — Bill orange-yellow, black for nearly its terminal half, 

 the extreme points of both mandibles j'ellowish ; robust, deep at the base ; 

 culraen markedly declinato-convex, eminence at symphysis well developed ; in 

 total length from one to two-tenths of an inch longer than in S. Mrundo. The 

 black pileum does not extend so far down on the sides of the head as it does in 

 hirundo, barely embracing the eye (the lower lid of which is white), and leav- 

 ing a considerably wider white space between the eye and commissural edge 

 of superior maxilla than in hirundo. The color of the back hardly differs ap- 

 preciably from that species ; it is perhaps a shade lighter. The wings are com- 

 paratively considerably shorter than in hirundo, being absolutely a little less, 

 though Forsteri is a larger bird. They are very light colored, being strongly 

 silvered with the peculiar hoariness common to most of the species of the 

 genus ; this lighter color is very observable even on the coverts. The outer 

 web of the first primary is not black, but silvery like the others ; all the prima- 

 ries want the very decided white space on the inner webs which exists in hirundo 

 and macroura ; there are indications of it, indeed, on the three or four outer 

 primaries, but the others are a nearly uniform dusky-gray, moderately hoary. 

 The entire under parts are white, with scarcely a trace of the plumbeous 

 which is so evident in hirundo, and amounts to so decided a color in macroura. 

 The tail is a slightly lighter shade of the color of the mantle, separated from 

 the latter for a short space by the decidedly white rump. The lateral feathers 

 are much more lengthened than in hirundo, the elongation generally quite 

 equalling that of macroura, and sometimes even exceeding it. These two • 

 lateral feathers are white on the outer web, dusky-gray on the inner. This 

 being exactly the reverse of hirundo, and a very noticeable feature, was the first 

 to draw attention to the bird, and this character being so tangible and conve- 

 nient, writers have perhaps laid too much stress upon it, to the exclusion of 

 others, quite as evident and more important. The feet are bright orange, 

 tinged with vermillion ; the tarsus shorter than the middle toe and claw; the 

 feet longer and stouter, by over -10 of an inch, than the sames parts in hirundo. 

 When the primaries become old, i e., at the approach of the spring or autuma 

 moult, before the species begins to put on its complete summer or winter livery, 

 the primaries lose their beautiful silvering, and become plain brown, their 

 shafts inclining to decided yellow. They have then also distinct white spaces on 

 their inner webs, nearly as well marked as in hirundo or macroura. 



Adult, winter plumage. — The bill loses the bright orange-yellow which exists 

 in summer, the black encroaching upon it, so that it becomes almost wholly 

 dusky. The base of the under mandible in dried skins appears as if it might 

 have been flesh-colored in life. The feet also lose their bright color, and in- 

 cline to a dusky-yellowish. The black pileum is more or less mixed with 

 white, the white predominating on the forehead so as to leave it nearly pure ; 

 there is always considerable black left on the nape, and also a broad band on 

 the side of the head, embracing the eye, and reaching to the nape behind, ex- 

 act!}' as represented in Audubon's plate of S. Havelli. The long lateral tail 

 feathers become greatly shortened, so as to be but scarcely, if at all, longer 

 than those of hirundo during the breeding season. The color of the inner webs 

 becomes darker, though it does not extend sofar towards the base of the feather; 

 sometimes it invades the outer web also, towards the tip. 



Young of the year, before the first moult. — Bill every way considerably smaller^ 



1862.] 38 



