220 TEXT-BOOK OF ZOOLOGY 



(b) The edges and the hooked tip of the bill are horny, and adapt the 

 beak for cutting off aquatic plants and for holding fast prey of a slippery 

 description (amphibians, fishes). 



(c) The outer edges of the lower and the inner edges of the upper 

 beak are furnished with numerous leaf-like horny plates or lamellae, 

 which, when the beak is closed, interlock with each other. (The upper 

 beak is broader than the lower beak.) 



(d) The tongue is large and fleshy, and provided at its edges with 

 horny fringes. By these arrangements 



(e) The beak, which, moreover, is broad and flat, is converted into a 

 perfect " strainer." (Compare with whale and herring.) When a 

 portion of mud has been taken up, the water is forced out by the tongue, 

 and flows out over its fringes and through the grooves at the edge of the 

 beak, so that only the solid portions are retained. The tongue, being 

 endowed with a fine tactile sense, then separates the eatable constituents 

 from the uneatable portions. (Why does the duck, " the pig among 

 birds," sift the mud of pools and gutters ?) Swimming animals, however 

 small, are captured in the same manner. 



4. The duck possesses a muscular gizzard like the fowl, and, like the 

 latter bird, takes in sand and pebbles with its food. 



5. When the ponds and lakes become covered with ice, the wild ducks 

 migrate in large flocks to the South. The few which remain betake 

 themselves to rivers and streams, and if these freeze they also are com- 

 pelled to take their departure. 



D. Enemies. 



The duck is zealously pursued by the sea-eagle, the goshawk, sparrow- 

 hawk, and other birds of prey, as well as by the otter and marten, 

 while many of the young also fall a prey to rats and crows. Its chief 

 enemy, however, is man, who hunts it for the sake of its palatable 

 flesh. 



1. The water and reeds amidst which it lives afford it good protection. 

 (Say which of its enemies are incapable of pursuing it into such places.) 



2. When surprised by birds of prey, it seeks to escape by diving. 



3. Their greyish-brown, dark-spotted, inconspicuous plumage serves 

 to hide female and young to a considerable extent among the reeds ; they 

 are also clever at " ducking " on the approach of danger. The " breeding 

 plumage " of the male in the later part of the winter and in spring is very 

 handsome, the head and upper part of the neck being of a beautiful 

 metallic greenish-blue colour, with a white band on the lower throat ; the 

 breast is chestnut brown ; the wings are ornamented with a beautiful blue 

 white-edged spot the so-called speculum. (What are the colours of the 



