86 



The National Geographic Magazine 



Photo from the Biological Survey 

 A MONUMENT TO THE INDUSTRY OF BARN OWLS 

 Field Mouse skulls found under owl roost in Smithsonian tower, Washington (see page 87) 



So, naturalists observe, a flea 

 Has smaller fleas that on him prey; 

 And these have smaller still to bite 'em, 

 And so proceed ad infinitum. 



After due recognition of the part in- 

 sect parasites play in the econonry of 

 nature, it is evident that, unassisted, they 

 are unequal to the task of keeping insect 

 life in a proper state of equilibrium. In 

 this work birds play an important, though 

 it may be relatively a somewhat sub- 

 ordinate part. Had parasitic and pre- 

 daceous insects been equal to the task of 

 holding in check insect pests, there would 

 be no place in the world for insect-eating 

 birds. In the progress of evolution, how- 

 ever, long after insects and insect para- 

 sites appeared, birds found a place va- 

 cant, which even their reptilian ancestors 

 had not been able to occupy, and pro- 

 ceeded to fill it. Having once gained a 

 place in the world, birds entered into a 

 competitive struggle with each other and 

 with other insect-eaters. In the course of 

 time they developed into a great number 

 of families, each distinguished by pecul- 

 iarities of form, plumage, and habits, and 

 each endowed with methods of its own in 

 the pursuit of food. That so many birds 

 are insect-eaters is an index alike of the 

 enormous reproductive capacity of insects 



and the inadequacy of the forces that 

 warred on insects before the advent of 

 birds. 



HAWKS AND OWLS ARE NOT MARAUDERS 

 BUT MOST BENEFICIAL 



The popular idea regarding hawks and 

 owls is that they are nothing but robbers 

 and bold marauders. Their real charac- 

 ter and the nature of their services to 

 man are generally overlooked. The fact 

 is that the great majority of our hawks 

 and owls are beneficial, and spend the 

 greater part of their lives in killing small 

 rodents, most of which are always and 

 everywhere noxious. Hawks and owls 

 are long-lived birds, as birds go, and this 

 fact gives a hint of their importance in 

 the eyes of nature and of their value as 

 servants of man. 



The work of hawks and owls is com- 

 plementary. All hawks are diurnal, and 

 hunt their prey between the hours of day- 

 light and dark. Owls, on the contrary, 

 are chiefly nocturnal, but do much of 

 their hunting in the early evening and 

 morning hours, or by moonlight, and 

 when pressed by hunger or when feeding 

 young, they sometimes hunt by day. 

 Hence, between them, hawks and owls 



