172 



The three methods of studying the food of birds need not 

 be discussed here, since they are the usual methods of ascer- 

 taining the kind and amount of food consumed. By their use 

 ornithologists have definitely shown that practically all of the 

 injurious insects on the mainland have their enemies among 

 the birds, and that often the amount of insect food consumed is 

 enormous. Owing to the active nature of birds they demand 

 large quantities of food. It has been sho^vn that sixteen ca- 

 naries (kept by Stanley) ate one-sixth their weight daily. Her- 

 rick observed three young red-winged blackbirds to be fed 40 

 times in four hours ; four young king birds were fed ninety-one 

 times in four hours, four young song sparrows were fed seven- 

 teen times in four hours, four young song sparrows were fed 

 seventeen grasshopper nymphs and two spiders in sixty-seven 

 minutes, while a house wren made one hundred and ten visits 

 to her nest in four and a half hours and fed one hundred and 

 eleven insects and spiders to her young. 



The relation of insect outbreaks and the damage done by 

 to crops fluctuates greatly. To obviate this a check should ]>e 

 provided by nature that would be always at hand and ready to 

 feed on any new pest that appears, without being too particular 

 as to the exact family and species to which the pest belongs. 

 Birds meet the requirement better than any other animal. They 

 are alert and active and mounted on swift wings. In more than 

 one instance they have proven their ability to work together for 

 the common good. Two illustrations selected almost at ran- 

 dom from published data are given to show the way bird con- 

 trol works out on the mainland. 



An observation conducted by Forbes in an orchard badly in- 

 fested with canker woims is of interest. He shot and examined 

 one hundred forty-one specimens. Of the thirty-five species 

 he found that twenty-six species had been eating canker worms 

 and eighty-five specimens, that is 72 per cent, of the species and 

 60 per cent, of the specimens, had eaten the w^orms. Of the 

 entire lot 35 per cent, of their food consisted of the canker 

 worms. He compared this result with the normal May food of 

 the birds and found that birds of varying sizes and habits had 

 migrated to the outbreak; that wrens, blue jays, meadow larks, 

 etc., etc., were among them; that in addition to the canker 

 worms a sufiicient per cent, of their normal food of different 

 kinds had been eaten to prevent its increase ; and that with one 



