SAFETY DEVICES IN BIRDS WINGS GRAHAM 



295 



ratio is length divided by breadth, so if one wants tlie aspect ratio 

 of a bird's wing, the mean breadth must be taken. Some aspect ratios 

 are given in the table at the end of this paper. 



Game birds, such as the partridge, pheasant, and blackcock, are 

 excellent examples of the type that can not afford to have long, nar- 

 row wings. Instead, they have multislotted, broad, square-tipped 

 ones. Blackcock and pheasants actually have six slots in each wing, 

 and proportionately these slots are among the longest of any that 

 are found in British birds. 



Another factor which probably influences the shape of the wings 

 of these birds is their habit of lying close when disturbed, and then 

 getting up with tremendous acceleration. Long wings requiring a 

 big sweep, with slow strokes, would get in the way, and would permit 

 the acceleration to die away on the upstroke. 



Figure 31. — The first eight flight feathers of a partridge 

 IX. SLOTS IN FLAPPING FLIGHT 



Archibald Thorburn's excellent pictures of game birds in flight 

 and many others, have made everyone familiar with the appearance 

 of their wings, with their many-fingered tips. Figure 31 shows the 

 shape of the individual flight feathers of a partridge's wing, and 

 Figure 32 how they fit together and form the well-marked slots. 

 One should not be too sure that the action of this type of slot is 

 quite the same as that described already, because the broad parts 

 of the webs, inside the steps, are mostly so very short that they 

 can not have the same power to limit the separating of the feathers 

 as have those of a buzzard, for instance (fig. 4). This type of 

 stepping down is known to ornithologists as " basal emargination," 



The extreme squareness of the wing fits in with the theory of 

 wing-tip air spill; it is also possible that these slots may be of use 



