INTRODUCTORY 19 



who feed a species of green Parrot on the fat of Siluroid fishes ; the 

 feathers, as a consequence, becoming beautifully variegated with red 

 and yellow. Another race of South Americans change the colours 

 of Parrots by plucking out such feathers as they propose shall be 

 altered, and inoculating the spot from which the feather was taken 

 with the milky juice obtained from certain glands of a small toad. 

 The new feathers now appear of a brilliant yellow colour, and on 

 being plucked out, it is said, grow again of the same colour without 

 any fresh inoculation. 



Finally, we have a few remarks to make on the covering of the 

 beak and feet. The jaws of a bird, as we have already remarked, 

 no longer bear teeth, but are ensheathed in horny cases. In many 

 species, as in the Petrels, for example, the beak-sheaths, instead of 

 being entire, one for the upper and one for the lower jaw, are made 

 up of a number of separate pieces ; while in the Puffin, and one 

 of the Pelicans, ornamental plates are developed during the breeding- 

 season and shed immediately after. In the Pelican this plate is square 

 in shape, and borne on the ridge of the beak near its middle ; in the 

 Puffin it is triangular, and is attached to the base of the beak at each 

 side. 



The legs, as a rule, are covered, as in the reptile, in horny scales ; 

 but in some birds, as in Grouse, and Sand-grouse, and the Golden 

 Eagle, and many Owls, the shank of the legs, and often the toes also, 

 are covered by long feathers not unlike long, silky hairs, and quite 

 different in character from the quill-like feathers on the legs of the 

 domesticated races of Pigeons and Fowls. In some birds a delicate 

 skin takes the place of scales. 



The claws of birds vary greatly in shape, according to whether they 

 play any part or not in the capture of the food. Thus they may attain 

 a relatively enormous size in Birds of Prey, where the claw of the 

 hind-toe is especially large ; here the feet are used to hold living prey 

 securely. Some species, indeed, as the Goshawk, for instance, kill 

 their prey by means of the feet and clav/s. In the Jacanas, birds of 

 the Plover tribe, the claws attain an enormous length, forming long, 

 pointed rods, which with their tremendously long toes serve to enable 

 them to walk on the delicate floating weeds of the rivers which these 

 birds haunt. In some other birds, as for example in the Cassowary, 



