326 KORXn AMERICAN BIRDS. 



Family HIRUNDINID^. — The Swallows. 



Char. Bill short, triangular, very broad at base (nearly as wide as long) and much de- 

 pressed, narrowing rapidly to a compressed, notched tip ; mouth opening nearly to the 

 eyes. Primaries nine, graduating rapidly less from the exterior one ; tail-feathers twelve. 

 Feet weak ; tarsi scutellate, shorter than middle toe and claw. Number of joints in toes 

 normal ; basal joint of middle toe partially or entirely adherent to lateral toes. Wings 

 long, falcate. Tail forked. Eyes small. Plumage compact, usually lustrous. All the 

 American species with a white patch on the sides under the wing, and with the iviils 

 hazel or brown. 



The Hinindinidce form a very well marked group of birds easily distin- 

 guislied from all others. They exhibit a close resemblance, in external aji- 

 peanince and habits, to the Cypselidcp. ; from wliich, ai)art from the internal 

 .structnre, they are reailily distinguished by the possession of nine, instead of 

 ten primaries ; twelve, instead of ten tail-feathers ; scutellate tarsi, toes with 

 normal number of joints (1, 2, 3, and 4, respectively, exclusive of ungual 

 phalanges), instead of a different proportion ; differently shajjed nostrils, etc. 

 In both families the wings are developed to an extraordinary degree ; the 

 outer primary nearly twice or more than twice the length of the inner, and 

 enabling its possessor to sustain flight almost indefinitely. The relations of 

 the family among the Oscincs apjiear closest to the Old World Muscicajjidw. 



In comparing the wings of the Hirundinidm with those of the Cypsdidce, 

 we readily notice one of the essential characters of the Oscincs, namely, that 

 the gi'eater wing-coverts hide only half or less than half of the secondary 

 quills, instead of reaching much beyond their middle, or nearly to the end. 

 (See Sundevall, Ornith. S3\st.) 



The precise character of scutellation of tarsus is somewhat difficult to 

 make out, owing to a tendency to fusion of the plates, although not essen- 

 tially ditierent I'rom most Oscines. There is a series of scutellaj along the 

 anterior face of the tarsus, and a longitudinal plate on each side, meeting, but 

 not coalescing, behind. The anterior scutellai sometimes appear to fuse into 

 the outer lateral plate ; or sometimes the latter is more or less subdivided ; 

 the inner plate is generally more distinct from the anterior scutelhe, and 

 usually entire, excejit jjerhaps at the lower extremity. 



Genera of North American Hiriindinidse. 



A. No.strils broadly oval, or circular ; opening upwards and forward, and exposed ; 

 without overhanging membrane. 



a. Edge of wing smooth. Tarsus short, stout; equal to middle toe without 

 claw; feathered on the inner side above. Nostrils almost or entirely without 

 membrane. 



Bill stout; culmen and commissure much curved. Frontal feathers 

 without bristles. Tail deeply forked. Color lustrous-black ; belly and 

 crissum sometimes white ......... Prof/ne. 



