64 THE MIGRATION OF BIRDS. 



In the first place birds must be in good condition 

 before their long pilgrimage can be undertaken 

 with any degree of comfort or hope of success. 

 A flight of many thousands of miles requires much 

 physical exertion ; the fatigues of such a long 

 journey can only be undergone with success, and 

 the perils reduced to a minimum, by birds capable 

 of performing the distance in a reasonable time, 

 and withstanding the enormous constitutional 

 strain. It is a rule almost without exception that 

 the wings of migratory birds are long and pointed 

 — a form best adapted not only for sustained but 

 rapid flight. It may also be remarked that the 

 birds which cover the longest distances have the 

 most pointed wings. The Turnstone, with its 

 enormous migration flight of ten thousand miles 

 or more, has a long pointed wing, the first primary 

 being the longest, and this is the rule throughout 

 the CHARADRiiDyE, the only exceptions being of 

 species whose flights are very short or dispensed 

 with altogether, as in Phegornis: the Swallow's 

 wings are equally pointed. The laws of use and 

 disuse determine the shape of the wing of a bird. 

 The wings of a bird vary according to the amount 

 of flight indulged in by their owner. Birds that fly 

 much have pointed wings ; birds that fly little have 

 short and rounded wings ; whilst birds that rarely 

 fly at all eventually degrade into species utterly 

 incapable of flight, as was the case with the now 

 extinct Great Auk, and is the case with the still 

 existing Antarctic Penguins. Long pointed wings. 



