EXTERNAL PARTS OF BIRDS. — THE FEET. 



131 



Fig. 48. — Semipal 

 ination in Ereunetts 

 iiat. size. 



Fii;. A.). — feemj- 

 palniateil bases of 

 toes of Symphemia ; 

 nat. size. 



It is actually thi. 



exliibit the transition from the perching to the gradient focjt, in some reducti<m of the hind toe, 

 which is nevertheless in most cases still on the same level as the rest (fig. 38, V). In the 

 gallinaceous or rasorial (Lat. rasor, a scraper) birds, which are essentially terrestrial, and 

 noted for their habit of scratching the ground for food, the hind toe is decidedly elevated and 

 shortened in almost all of the families (fig. 35). Such reduction and uplifting of tlu^ hallu.x is 

 carried to an extreme in inost of tlie waders, or g7'al- 

 latores, in many of which tliis toe disapiiears (figs. 

 38, a, 39). It is scarcely practicable to recognize special 

 modifications of such gradient or grallatorial feet, since 

 they merge insensibly into one anotlier. The herons, 

 which are the most arboricole of the waders, exhibit a 

 reversion to the iusessorial type, in the length a.ud in- 

 cumbency of the hallux. TIk; ujode of uinon of the 

 front toes of the walkers and waders is somewhat char- 

 acteristic. The toes are either cleft quite to the base, 

 or there joined by small webs ; probably never actually coherent. Such 

 basal webbing of the toes is called semipalmation ("half-webbing"), 

 same thing that occurs in many birds of prey, in most gallinaceous birds, etc. ; the term is 

 mcjstly restricted, in descriptive ornithology, to tliose loading birds, or grallatores, in which it 

 occurs. Sucli basal webs generally run out to the end of the first, or along part of the second, 

 phalanx of the toes ; usually fiirther between the outer and middle 

 than between tlie middle and inner toes. Such a foot is well illus- 

 trated by the semipalmated plover {^gialite.'i semipalmaius) , 

 seinipalmated sandpiper (Eretmetes pusilliix, fig. 48), and wUlet 

 (Symphemia semipalmata, fig. -19). In a few wading birds, as the 

 avcjcet and flamingo, the webs extend to the ends of the toes. 

 This introduces us at once to the third main modification of the 

 f(]ot, 3. The natatorial type. Here the foot is transformed into 

 a swimming implement, usually with much if not entire abrogation 

 of its function as foot or hand. Swimming birds with few ex- 

 ceptions are notoriously bad walkers, and few of them are perchors. 

 The swimming type is presented under two principal modifica- 

 tions : — (a.) In the palmate or ordinary webbed foot, all the fi-ont 

 toes are united by ample webs (fig. .50). The palmation is usually tern, Sterna forsferl; nat size, 

 complete, extending to the ends of the toes; but one or both webs may be so deeply incised, 

 that is, cut away, that the palmation is practically reduced to semipalmation, as in terns of 

 the genus Tfydrochelidon (fig. .51). The totipalmate is a special case of palmation, in 

 which all four toes are webbed ; this characterizes tlie whole order 

 Steganopodes (fig. 52). (b.) In the lobate foot, a paddle results n<jt 

 from connecting Avebs, but fnun a series of loie.i or flaps along the 

 sides of the individual toes; as in the coots, grebes, phalaropes, and 

 sun-birds {Heliornithida;) . Lobation is usually associated with semi- 

 palmation, as is well seen in the grebes (Podia'pedidce) . In the snipe- 

 like phalaropes (Phalaropodidm), lobation is present as a modification 

 of a foot otherwise quite cursorial. The most emphatic cases of loba- 

 tion are those in which each joint of the toes has its own flap, with a 

 free convex border ; the membranes as a whole therefore present a scol- 

 loped outline (figs. 53, 53 ibis). Such lobes are merely a development 

 of certain marginal fringes or processes exhibited by many non-lobate or non-palmate birds. 

 Thus, if the foot of some of the gallinules be examined in a fresh state, the toes will be seen to 



Fig. 50. — Palmate foot of a 



Fig. 51. — Incised pal- 

 mation of HijdrochKlldon 

 lanformls ; nat. size. 



