98 THE BIOLOGY OF BIRDS 



mouth ; the jacanas or galHnules which have very long 

 toes, suited for walking on the floating leaves of water-lilies, 

 lift aquatic plants to their bill and pick oli" the small animals ; 

 the fowl-like birds use their strong blunt claws to scratch 

 the ground and the wood-storks stir up the mud in the 

 shallow pools with their toes ; the secretary bird, a kind of 

 terrestrial vulture, strikes the snake with its foot and some- 

 times kills with one forward kick ; the owls can bend their 

 fourth toe backwards beside the first toe, and this forms 

 an effective instrument for catching, crushing, and carrying 

 a mouse ; the osprey has a similar trap for fishes, and their 

 slipperiness is met by sharp hard pads below the toes. The 

 eagle's foot with the first toe backward and the others 

 forward, worked by powerful muscles and tendons, and 

 armed with sharp strong claws, is unsurpassable. The 

 golden eagle on the moor seizes the grouse among the 

 heather without stopping in its flight, and carries it in its 

 talons to its eyrie. There it holds the dead bird with 

 one foot, while it plucks off the feathers and tears up the 

 flesh with its bill. Mr. Beebe notes that in vultures which 

 feed upon carrion the toes have lost their clasping power. 



§ 3. The Food-canal and its Annexes 



The mouth cavity is lubricated by the secretion of the 

 salivary glands, which differ greatly in their degree of 

 development. They are large in birds like woodpeckers, 

 in which the tongue is covered with viscid secretion, useful 

 as a glue in insect-capture. They are peculiarly large in 

 the sea-swift, Collocalia, where the salivary secretion, 

 largely consisting of mucin, is used to make the nest. The 

 digestive function of the salivary juice (turning starch into 

 sugar) does not seem to be very important in birds, which 

 are so much given to " bolting " their food, but no doubt 

 some of the secretion will accompany the food into the 

 gullet and into the crop if there is one. 



The muscular region at the back of the mouth is the 

 pharynx, and its function is to grip the food in the process 



