298 On the Ornithology of Wilts. 



and enabled by tbeir spreading toes to run lightly over water-plant s 

 and the softest mud without danger of sinking in. The swimmers 

 supplied with feet and legs, serving them for oars and rudders, 

 whereby to impel forwards their bodies on the waves, or to seek 

 their food far below the surface of the water. These are all instru- 

 ments so exactly and so perfectly adapted to their respective uses, 

 that we can conceive nothing more applicable; and they are plain 

 and easy marks to us for ascertaining the general habits and class- 

 ified position of any bird we observe. Our examination of the 

 subject might well stop here, but before concluding this paper, I 

 would call attention to a few remarkable instances of structure in 

 regard to the feet, as displaj-ed by some particular species. 



The " Osprci/" alone of all the family Falconidae lives entirely 

 upon fish, and the nature of its prey being therefore different from 

 that of its congeners, it requires and is furnished with feet pecu- 

 liarly fitted for seizing and holding securely the slippery denizens 

 of the deep: in the first place, in lieu of the long feathers which 

 commonly clothe the thighs of the falcon race, short ones are 

 substituted, which leave more freedom for action in the water; 

 then the outer toe is reversible, and can at pleasure be turned 

 backwards, so that, as Yarrell tells us, it is the custom of the bird 

 to "seize the prey across the body, placing the inner and outer 

 toes at right angles, with the middle and hind toes; and digging 

 in the claws, to hold the fish most firmly by four opposite points." 

 Moreover, the soles of its feet are remarkably rough, and covered 

 with protuberances; while the talons are very much curved, sharp 

 and strong, that of the outer toe being the largest, which is contrary 

 to the usual custom; and all these peculiarities tend to the holding 

 with greater security the slimy victims on which it lives. 



The "Nightjar," which feeds at twilight, presents another very 

 peculiar formation of foot; this is small and weak in proportion to 

 the size of the bird, but is remarkable for the claw of the middle 

 toe, which is particularly long and serrated or pectinated on its 

 inner edge, and resembles a comb with seven or eight teeth. Now 

 the food of the nightjar consists of moths, but especially of fern- 

 chaffers, beetles, and such late flying insects, the legs of which are 



