Il8 THE BOOK OF MIGRATORY BIRDS 



of Gesner and Aldrovand, to consider the peculiar struc- 

 ture of the foot in parrots and woodpeckers, with two toes 

 before and two behind, as so peculiarly characteristic of 

 climbing birds that in systematic classifications the birds 

 which have their toes so placed are denominated climbing 

 birds (Scansores) ; but, unfortunately for this division, 

 many species which have the feet so constructed have never 

 been observed to climb, such as the cuckoo and the 

 wryneck, while many species which do climb, such as the 

 Nuthatch (Sitta) and the Creeper (Certhia) have their toes 

 placed in the usual manner. 



White's remarks on the walk of birds are well worth 

 quoting. "Most small birds," he says, "hop; but wag- 

 tails and larks walk, moving their legs alternately; all 

 the duck kind waddle; divers and auks walk as if fettered, 

 and stand erect on their tails ; crows and daws swagger 

 in their walk; woodpeckers use their tails, which incline 

 downward, as a support when they run up trees; parrots, 

 like all other hook-clawed birds, walk awkwardly, and 

 make use of their bills as a third foot, climbing and de- 

 scending with ridiculous caution. All the poultry 

 (Gallina?) parade and walk gracefully and run nimbly." 



It is worthy of remark that, as the bones commonly 

 considered as belonging to the leg in birds correspond 

 to the heel of the human foot, all birds must walk, as we 

 may say, on tiptoe. As they have their centre of gravity, 

 however, not directly over their legs, but more forward, 

 it requires peculiar contrivances in their formation to enable 

 them to balance themselves on their toes. Accordingly, 

 birds have their toes for the most part proportionately 

 much longer than other animals, while the great flexion 

 of the leg upon the thigh brings the toes more under the 

 centre of gravity. 



Birds have also this further peculiarity, that the stand- 

 ing posture is their state of most perfect rest, arising from 

 the structure of their legs, as first explained by the old 

 Italian naturalist, Borelli. The tendons of the muscles 



