BIRDS AND THE WEB OF LIFE 413 



(3) Birds that help man's operations, more or less 

 directly ; thus some small birds pollinate flowers and some 

 distribute useful plants, many like gulls and kites are very 

 useful scavengers. 



(4) Birds that hinder man's operations. This must be 

 a very short list, restricted to a few cases like aggressive 

 ostriches. 



(5) Birds that injure useful animals and plants, e.g. 

 house sparrows which spoil crops and drive away insecti- 

 vorous birds ; wood-pigeons which eat enormous quantities 

 of grain ; herring-gulls when they become very vegetarian 

 and destroy full-grown turnips and the ears of corn in the 

 sheaves ; the kea-parrot that kills sheep in New Zealand. 



(6) Birds that spoil or destroy man's permanent products, 

 e.g. house-sparrows which sometimes make an ivy-covered 

 house intolerably dirty ; starlings in so far as they do damage 

 in a farm-steading. 



(7) Birds that keep a check on creatures {a) that hinder 

 man directly, {b) that injure useful animals and plants, and 

 {c) that spoil or destroy man's permanent products. 



Thus {a) some birds destroy snakes, others rats, others 

 mosquitoes. 



{b) Others check the increase of voles and sparrows, 

 plant-lice and scale-insects. 



{c) Others check various injurious insects that destroy 

 man's permanent products. 



The uses of birds are much more varied than one might 

 think, and we take a few illustrations from an interesting 

 lecture by Mr. Hugh S. Gladstone (1920). Canaries, being 

 about fifteen times more sensitive than man to poisonous 

 gases are used in this connection in mines and were used in 

 the war. ... In 1910 about ^^i, 500,000 worth of ostrich 

 feathers were imported into Great Britain, in 1919 more 

 than ^30,000,000 worth of eggs and poultry. Some 

 domestic strains of poultry are veritable egg machines, laying 

 as many as 3000 eggs in a lifetime, whereas the original 

 Jungle Fowl in a wild state lays at the utmost forty or fifty. 

 ..." After the conquest of Gaul relays of pigeons carried 



