Sky Sweepers 259 



open, the beginning of preening, probable flight distance per 

 day, and feeding habits. There are many actual experiences 

 of field observers to verify or contradict my own field find- 

 ings. And if I wish to go further, I can always consult the 

 writings of men who have specialized in fields in which I am 

 personally interested. 



My research need not be limited to the swallows of the 

 marsh. The literature discusses the members of the swallow 

 family all over the world. I can find how widely the birds 

 are distributed and much about their habits, size, and speed. 

 There will be big birds and very little ones, and highly col- 

 ored species which add so much interest from a popular 

 standpoint If I want foreign information on technical prob- 

 lems, it will be available, often in greater detail than in the 

 writings of Americans in the same fields. 



We have made considerable progress since Aristotle wrote 

 about sw r allows. Man, not content with blindly following the 

 lore of the ancients, and freed from the shackles of dog- 

 matic religion, has struck directly at the core of truth. By 

 intelligent observation and use of the scientific method, facts 

 are discovered and their significance recognized. Careful 

 field studies, detailed analyses of the natural environment, 

 expeditions of trained personnel, publication of findings, bird 

 banding, and the building up of specimens collected for 

 lab orator} 7 study— all have played their part in our advance 

 of knowledge so that a few tattered legends have been re- 

 placed by a mass of concrete facts. 



It all sounds delightfully final until I raise questions like 

 this: We know many things about migration, but exactly 

 what causes it? Much is known about the return of swallows 

 to the identical spots which they occupied the year before, 

 but precisely how do they do it? And when no eager hands 

 are raised to answ T er and explain, I feel that, perhaps after 

 all, we are still a long way from the solution of the real 

 problems. 



