320 



SYSTEMATIC SYNOPSIS— PASSEBES— OSCINES. 



is scarcely or not half as long as the 1st ; secondaries and their coverts also very short ; aU 

 these quill-feathers broad and stout. An acute, thin-hladed and somewhat falcate wing, of 

 surpassing volatorial power, results from these modifications. Tail of 12 reotrices, perhaps 

 abnormally only 10, usually forked, or at least emarginate, and often deeply forflcate, the 

 outermost feathers being in this latter case narrowly linear in shape for a considerable dis- 

 tance. Feet short, small, 



and weak, ill-adapted to 

 secure foot-hold, and very 

 badly formed for walk- 

 ing. Swallows scarcely 

 use their feet for locomo- 

 tion, relying mainly upon 

 their prowess of jHuion. 

 The tarsal envelope thor- 

 oughly Oscine in struct- 

 ure, being scuteUate in 

 front and laminate behind; 

 it is sometimes partially, 

 or almost entii-ely, feath- 

 ered ; the tarsi are com- 

 monly shorter than the 

 lateral toes. The digits 

 possess the normal number 

 of phalanges; the basal 

 phalanx of the middle 

 digit is commonly coherent 

 • with one or both lateral 

 toes ; the hallux is ordi- 

 nary, and not reversible. 

 The digits are commonly 

 naked and scuteUate, rare- 

 ly feathered to the claws. 

 The claws are compara- 

 tively strong, compressed, 

 well-curved, and acute, 

 apt for clinging. The 

 plumage is soft, smooth, 

 and blended, most fre- 

 quently glossy or even 

 iridescent, but sometimes 

 lustreless. Head short, 

 broad, and depressed ; 

 neck short. Mouth capa- 

 cious, its greatest width 

 equalling that of the head. 

 This is a perfectly natural group, well distinguished by the foregoing characters. The 

 swallows alone represent, among Osoines, the flssirostral type of structure ; they have a close 

 superficial resemblance to the swifts and goat-suckers of another order, but the relation is one 

 of analogy, not of afiinity, though all. these birds were formerly classed together in the highly 

 unnatural " order" Fissirostres. (See beyond, under CypseUdtB and Caprimulgidce.) 



Fig. 180. — Upper, European House Martin, Chelidon wbica ; lower, Bank 

 Swallow, Cotile ripa/ria. (From Dixon.) 



