BIRDS OF THE AIR. 339 



Chapter IX. 



BIRDS OF THE AIR. 



There are no birds that so well deserve the designation 

 "fowls of the air" as those that get their subsistence by pur- 

 suing flying insects. Eagles and Vultures, Frigate Birds, 

 Albatrosses, and some other sea birds, are endowed with 

 great powers of flight, but all must descend to earth or 

 water for their food ; but Swallows, Swifts, and Nighthawks 

 win their sustenance from the air. They may be said to 

 live in the air, as, with few exceptions, they seldom alight 

 except to rest or to attend to their domestic afiiairs. 



Unfortunately, the precise character of the food that many 

 of these insect-eating birds procure high in air is not well 

 known. We see the Swifts and Swallows darting about at 

 great heights on clear summer days. We know that they 

 must be catching flying insects ; but what insects are flying 

 at such a height, and why? They must be winged imagoes. 

 Have they finished the business of life, and are they then 

 sporting for a few brief hours in sunlight before death over- 

 takes them ? Are they migrating on the wings of the wind 

 to fresh fields? Are they useful, or injurious, insects? No 

 one knows. 



"When Swallows or Swifts are flying low their food can be 

 studied, and we have some definite information regarding its 

 character at such times. They are known to take many 

 parasitic Hymenoptera, but whether these insects are taken 

 before or after they have propagated, whether most of them 

 are mainly beneficial, or injurious, parasites, we have little 

 information. Therefore, the eflFect produced by this habit 

 of these birds is not well understood. We know, however, 

 that many injurious insects, such as flies, gnats, mosquitoes, 

 moths, beetles, and plant lice, when about to reproduce their 

 kind, are captured by these feathered skimmers of the air. 

 We know that the Swallows pursue insects all day, until the 



