144 



The Bird 



there is such specialization for feeding on particular 

 varieties or portions of plants. We find fruit- and grain- 

 eaters, besides those which feed almost entirely on buds, 

 leaves, berries and nuts, nectar, sap, and even pollen. 

 Lichens form a considerable item in the bill of fare of 

 ptarmigans, the Arctic grouse. We have even dedicated 

 certain plants to birds which show a decided partiality 

 for them, — duckweed and partridge-berry. 



Fig. 109. — Vireo, an insect-hunter, with a delicate, hooked bill. 



There is no doubt that a great many plants benefit 

 from the cross-fertilization of their flowers by humming- 

 birds carrj'ing the pollen from blossom to blossom. Of 

 one of the sugar-birds of South Africa it is said: ** When 

 sucking up the nectar of one of the larger protea-blossoms, 

 the bird j^erches on the edge of the flower, plunges its 

 long l)ill and the greater part of its head downwards 

 among the petals, and retains it in this position until 



