THE HOVERING OF THE KESTREL. 205 



spot and watch like a cat for a minute or two for mice 

 or beetles. For rest they always seek a tree. 



Now, having briefly sketched his general manner, 

 let us return and examine the details. In the first 

 place, he usually rises slightly, with outstretched 

 wings, as if about to soar at the moment of com- 

 mencing hovering. The planes of the wings are then 

 inclined, and meet the air. At the instant of stop- 

 ping, the tail is depressed. It appears reasonable to 

 conjecture that the slight soaring is to assist the tail 

 in checking his onward course, and to gain a balance. 

 Immediately the wings beat rapidly, somewhat as they 

 do in ordinary flight but with a more forward motion, 

 and somewhat as birds do when about to perch on 

 an awkward ledge, as a swallow at an incomplete 

 nest under an eave. The wings look more, in front, as 

 if attached to his neck. In an exaggerated way ducks 

 beat the air like this, with no intention of rising at 

 all, merely to stretch their wings. The duck raises 

 himself as he stands on the ground, stretches himself 

 to his full height, and flaps his wings horizontally. 

 The kestrel's wings strike downwards and a very 

 little forwards, for his natural tendency is to slip 

 forwards, and the object of slightly reversing his 

 vanes is to prevent this and yet at the same time to 

 support him. His shape is such that if he were rigid 

 with outstretched wings he would glide ahead, just as 

 a ship in a calm slowly forges ahead because of her 

 lines, which are drawn for forward motion. The 

 kestrel's object is to prevent his slip forwards, and the 

 tail alone will not do it It is necessary for him to 

 "stroke" the air in order to keep up at all; because 



