553 



HIRUNDINiE. 



SWALLOWS AND ALLIED SPECIES. 



The birds of which this family is composed have by several 

 recent authors been grouped into genera distinguishable by 

 slight differences in their organization, and more especially by 

 the sfreater or less emargination of the tail. Some of these 

 genera are perhaps founded on sufficient grounds; but our three 

 British species differ too little to sanction any subdivision of 

 the single genus, Hirundo, to which they have usually been 

 referred. As the characters of that genus will be given at con- 

 siderable length, it is unnecessary here to state more than is 

 absolutely essential. The Hirundinae have the bill short, much 

 depressed, broad at the base, compressed at the tip ; the head 

 broad and depressed ; the neck very short ; the body moderate ; 

 the feet very small, the claws compressed, curved, acute. The 

 plumage glossy and blended ; the wings very long and narrow, 

 the secondaries being very short and few ; the tail of twelve 

 feathers. The mouth is very wide ; the stomach elliptical, 

 muscular ; the coeca very small. They nestle in holes, or against 

 the face of rocks, buildings or trees, in which case they con- 

 struct a nest of mud, or of twigs held together by a glutinous 

 substance. The eggs are generally four or five, white, either 

 plain or spotted. All the species which breed in the cold 

 and temperate regions retire w^ithin the tropics in winter, 

 their exclusively insectivorous regimen rendering it impossible 

 for them to subsist when the cold is severe. Their extreme 

 activity, the elegance of their flight, and the attachment which 

 they shew to human habitations, render them universal ffivour- 

 ites. In the structure of their digestive organs, as well as in 

 their habits, they are nearly allied to the Myiotherinae, which 

 are equally migratory. 



