416 THE LIFE OF A BIRD. 



extremely powerful muscles act upon both the 

 mandibles, and cause them, when any object, such 

 as a nut, is placed between them, both to press it 

 powerfully and to give it a sort of wrench at the 

 same time; an effect which greatly favours the 

 action of the bill. A vast amount of force is thus 

 combined in the smallest possible compass; and 

 the perch upon which the parrot stands will often 

 give evidence of the power of its bill, while the 

 cleverness with which it manages to open its cage 

 door, to the annoyance of its owner, will also 

 testify to the delicate and skilful operations to 

 which it is equally applicable. The bill is also an 

 excellent aid in the action of climbing. 



Birds which feed on insects caught while hawk- 

 ing on the wing, are furnished with a peculiarly 

 formed bill, in order to assist in the capture of 

 their prey. The bill of the common goat-sucker 

 is a beautiful arrangement for this purpose, the 

 bill gaping to an extreme width and depth, and 

 furnished at the side with a delicate fringe, which 

 retains the unfortunate insects captured. The 

 heads of the swallow and swift are equally re- 

 markable for this feature, a wide-gaping deep 

 mouth : their heads, indeed, seem to be all mouth. 



