138 



GENERAL ORNITHOLOGY. 



have a narrow membranous margin running the whole length. The same thing is evident in 

 a great many waders, and on the free borders of the inner and outer toes of web-footed birds. 



In the grouse family 



(Tetraonidee) , mar- 

 ginal fringes are 



very conspicuous ; 



there being a great 



development of hard 



horny substance, 



fringed into a series 



of sharp teeth or 



pectinations (fig. 



35). These forma- 

 tions appear to be 



deciduous, that is, 

 to fall off periodically, hke parts of the claws of 

 some quadrupeds (lemmings). 



Fig. 52. — Totipalmate foot of 

 pelican; reduced. 



Lobate foot of a coot; reduced. 



Fig. 53 Ws.— Lobate foot of phala- 

 rope, Lobipes hyperhoreus ; nat. size. 



Claws and Spurs. — With rare anomalous exceptions, as in the case of an imperfect 

 hind toe, every digit terminates in a complete claw. The general shape is remarkably constant 

 in the class ; variations being rather in degree than in kind. A cat's claw is about the usual 

 shape : it is compressed, arched, acute. The great talons of a bird of prey are only an en- 

 largement of the typical shape ; and, in fact, they are scarcely longer, more curved, or more 

 acute than those of a delicate canary bird ; they are simply stouter. The claws of scansorial 

 birds are very acute and much curved, as well as quite large. The under surface of the claw 

 is generally excavated, so that the transverse section, as 

 well as the lengthwise outline below, is concave, and the 

 under surface is bounded on either side by a sharp edge. 

 One of these edges, particularly the inner edge of the middle 

 claw, is expanded or dilated in a great many birds ; in some 

 it becomes a perfect comb, having a regular series of teeth. 

 This pectination (Lat. pecten, a comb), as it is called, only 

 occurs on the inner edge of the middle claw. It is beautifully shown by all the true herons 

 (Ardeidce) ; by the whip-poor-wills and night-hawks (Caprimulgidce, fig. 41) : by the frigate 

 pelican (Tachypetes) ; and imperfectly by the barn owl (Aluco flammeus). It is supposed to 

 be used for freeing parts of the plumage that cannot be reached by the bill from parasites; 

 but this is very questionable, seeing that some of the shortest-legged birds, which cannot 

 possibly reach much of the plumage wnth the comb," possess that instrument. Claws are 

 more obtuse among the lower birds than in the insessorial and scansorial groups, as the 

 columbine and gallinaceous (rasoriaT) orders, and most natatorial families. Obtuseness is 

 generally associated with, flatness or depression ; for in proportion as a claw becomes less 

 acute, so does it lose its arcuation, as a rule. This is well iUustrated by Wilson's petrel 

 ( Oceanites oceanicus) , as compared with others of the same family. Such condition is carried 

 to an extreme in the grebes (Podicipedidce), the claws of which birds resemble human finger- 

 nails. Otherwise, deviations from curvature, without loss of acuteness, are chiefly exhibited 

 by the hind claw of many terrestrial Passeres, as in the whole family Alaudida; (larks), 

 and some of the finches {FringilUdai) , as the species of " long-sjiur " {Centrophanes) . But all 

 the claws are straight, sharp, and prodigiously long, in birds of the genus Parra (fig. 

 53 ter) ; these ja^anas being enabled to run lightly over the floating leaves of aquatic plants 

 by so much increase in the spread of their toes that they do not "slump in." Claws nrc 



