TASTE OF GRANIVOROUS BIRDS. 127 



gestible ball in their stomach, which they cannot 

 expectorate, and which is sure to kill them *." 



According to Colonel Montagu, granivorous birds 

 have some power of retaining the small stones 

 taken into the gizzard, or evacuating them when they 

 become polished and less useful, though they cannot 

 disgorge them as birds of prey do the pellets of bones 

 and feathers which they are unable to digest. He thinks 

 that in a state of nature birds swallow only a whole- 

 some portion of these stones, whereas domesticated 

 birds frequently devour too many. He has known 

 instances in which the whole cavity of the gizzard 

 was filled with gravel; and in particular he mentions 

 part of a brood of ducks, half grown, which swallowed 

 so great a quantity of gravel as not only to fill the 

 gizzard, but the crop and even the gullet: they soon 

 after diedf. 



In the swan and the goose, whose food is similar, 

 but different from that of the turkey, there is no 

 distinct crop, but the lower part of the gullet is 

 expanded so as to form a reservoir to store up the 

 food. This structure is perhaps peculiarly adapted 

 to act upon grass, which, according to Sir Everard 

 Home, " appears more difficult of digestion than any 

 other vegetable used for food ; and no preparation 

 hitherto employed has rendered the human stomach 

 capable of converting it into nourishment {." The 

 goose has the digestive glands more complex than 

 the swan, a peculiarity which may be probably ac- 

 counted for, as Sir Everard thinks, from the swan's 

 feeding on the weeds and coarse grass growing by 

 the sides of rivers ; whereas the goose, from feeding 

 on the common grass of the fields, is the only exclu- 

 sively grazing bird in this country . 



* Notes to White's Selborne, 8vo. edit. 1833. 



t Ornith. Diet. p. 498. 2d edit. 

 | Phil. Trans, 1810. Ibid. 



N 



