THE BLUE CAP. 319 



with the greatest certainty and from a considerable 

 distance, the leaf in which they can find something to 

 eat. When they leave these, or rather when the season 

 ' is so far advanced that there are not any caterpillars 

 upon the leaves, their hunting upon the trunks and 

 among the branches is as incessant. Their motions are so 

 rapid that one of them will hunt over the whole surface 

 of a pretty large fruit tree, round and round every 

 branch, in the course of a few minutes, and so intent 

 are they upon their sport, that one may stand close by 

 and watch them all the time, without their giving them- 

 selves the least alarm. The chief places on the wood 

 of an apple tree where insects and larvse lodge, and 

 eggs are deposited, are in the cracks and fissures on the 

 undersides of the branches ; and the dexterity with 

 which the blue-cap supports himself at these, until he 

 has captured the tenants, is very extraordinary ; and 

 while he runs and hops about, he keeps uttering his 

 rasping noise, as if he were whetting an instrument 

 with which to cut the tree down. That sound is not a 

 love note, neither does it appear to be a call note, but 

 an ordinary noise, a subject which has not been much 

 investigated ; but as many birds utter a noise when there 

 is no apparent excitement, it would be at least a grati- 

 fication of curiosity to know what purpose of their eco- 

 nomy is served by it. 



As the blue-cap is among the trees at all seasons, the 

 quantity of insects which it destroys, and the number 

 of which it prevents the existence, must be very great ; 

 and therefore it and its congeners, and indeed all the 

 scandent birds that feed upon insects, are to be re- 

 garded as nature's guardians of the orchard and forest ; 



