POOD OF SOME WELL-KNOWN BIEDS. 



treated together. All are residents of coniferous forests, from Avhich 

 they sometimes wander a short distance in winter. 



The great bulk of the food of these birds consists of the larvaj 

 of wood-boring beetles or moths. These are eaten with great regu- 

 larity throughout the year, but somewhat more in the colder months 

 than in summer. Unfortunately only 28 stomachs of Picoides air- 

 ticus (fig. 1) and 23 of P americanus were available for examina- 

 tion. In the first analysis the food divides into 88.69 per cent of 

 animal matter to 11.31 of vegetable ^or arcticus, and 94.06 per cent 



of animal to 5.94 



wood-boring cole- 

 opterous larvae. 

 These amount to 

 64.25 per cent with 

 arcticus and 60.66 

 with americanus. 

 Caterpillars, which 

 in this case are 

 mostly wood-bor- 

 ing species, amount 

 to 12.28 and 14.45 

 per cent for the 

 two birds, respec- 

 tively. This brings 

 the total of wood- 

 boring larvae, in- 

 cluding both cater- 

 pillars and beetles, 

 up to 77.13 per cent 

 for arcticus and 

 75.11 per cent for 

 americanus, or 

 more than three-fourths of the food of each species. Stomachs con- 

 taining 15 to 20 of these grubs are common and one held 34. Prob- 

 ably the stomach is filled several times each day, and it does not seem 

 unreasonable to assume that a bird will eat 50 of these insects every 

 24 hours for 6 months and at least 25 daily for the other half of 

 the year. At this rate one bird will annually destroy 13,675 of these 

 destructive grubs. Beetles other than wood borers amount to 3.41 

 per cent for arcticus and 10.39 for americanus. Ants constitute 6.35 

 per cent, of the food of arcticus and 8.29 of that of americanus. 



506 



Fig. 1 . — Arctic thrce-toofl woodpecker. 



