196 



GENERAL ORNITHOLOGY 



variations being rather in degree than in kind. A cat's claw is about 

 the usual shape : it is compressed, arched, acxite. The great talons of 

 a bird of prey are only an enlargement 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 bii'ds are very acute and much curved, as well 

 as quite large. The under surface of the claw is generally exca- 

 vated, so that the transverse section, as well as the lengthwise out- 

 line below, is concave, and the under surface is bounded on either 

 side by a sharp edge. One of tliese edges, particularly the inner 

 edge of the middle claw, is expanded or dilated in a great many 

 birds ; in some it becomes a perfect comh, having a regular series of 

 teeth. This j^ectination (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 goatsuckers 



Fig. 53 fer. — Foot oi Parra gymnostoma, nat. size, showing the long, straight claws. (From 

 Ridgway Mus. The simrred wing of the same bird is also shown. See p. 168.) 



{Capriviulgidce, Fig. 41); by the frigate pelican {Tachypetes) ; and 

 imperfectly by the barn-owl {Aluco flmnmeus). 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 with the comb, possess that instrument. Claws are 

 more oUuse among the loAver birds than in the insessorial and scan- 

 sorial groups, as the columbine and gallinaceous (rasoricd) 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 

 illustrated by Wilson's petrel (Oceanites oceanicus), as compared with 

 others of the same family. Such condition is carried to an extreme 

 in the grebes (Podicipedida'), 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 



