A STUDY OF ACQUIRED HABITS 65 



or demented woodpeckers. Why should there not 

 be such individuals among birds ? One point is 

 certain : so notable a habit could not long escape 

 detection, since it is a barnyard crime. He who 

 robs hen's nests gets caught — if he is a bird. 

 Either these occurrences are very rare, not seen 

 because of their extreme rarity, or they indicate 

 a new custom just coming in. And the same is 

 true of the habit of hoarding food ; it is rare, or 

 it is new. 



The frequency of such occurrences can be de- 

 termined only by observation ; but the time of 

 their origin might be approximated in another 

 way. If we could fix the date when the bird 

 could not have done what he is now doing for 

 simple lack of opportunity, we might say that the 

 habit has been acquired since a certain date — 

 as we have said of the English sparrow eating 

 maize, of the chimney swift nesting in chimneys, 

 and the cliff swallow building under the eaves. 

 But we have no such help on the case of the red- 

 head, which never has been without opportuni- 

 ties to scet birds' esfsrs and to kill other birds. 



But there is a parallel case in another species 

 where the date of an acquired habit can be 

 proved. In Florida the red-bellied woodpecker 

 has earned the names Orange Borer and Orange 

 Sapsucker because he eats oranges. It is true 



