BIRDS 



year. They have a high bodily temperature and lead 

 an active life, entailing a great expenditure of muscle 

 and nerve energy, with a considerable loss of heat, 

 consequently their requirements in the way of food are 

 large. Nature has provided for this in giving the bird 

 a strong and rapid digestion, which impels it to seek 

 food at frequent intervals. When the parent birds 

 have a nestful of youngsters to provide for, they are 

 on the war-path from daylight until dusk. A pair of 

 birds with four nestlings destroy as many insects as a 

 dozen single birds, because the rapidly-growing fledg- 

 lings require an abundance of food. Birds are not 

 only formidable foes of insects, but they help very 

 largely in keeping weeds and other forms of undesir- 

 able vegetation in check. Also they are largely 

 instrumental in forming forests, both by sowing tree 

 seeds broadcast, and by protecting the growing trees 

 against the ravages of insects. 



Birds which feed largely on fruit and berries do 

 not, as a general rule, digest the seeds ; these pass 

 through their digestive organs unchanged. 



On the contrary, the true seed-eating birds, which 

 feed chiefly on the seeds of weeds, digest the seeds 

 completely, and thus render man very valuable 

 services. 



When these birds attack corn-lands in unusually 

 large numbers, of course it lies with each farmer to 

 use his judgment as to whether the harm they are doing 

 is paid for in full or not by the weed seeds and insects 

 they devour. It must be remembered that birds lay 

 their eggs during the spring and early summer, conse- 

 vol. i. 23 3 



