GREY BREASTED MARTINS 339 



What often is taken for instinct really is a newly acquired 

 habit which, under other conditions, might be altered. Thus 

 it happened, on the following day, that the martins instinc- 

 tively commenced to build a new nest, but, from habit, used 

 the old site. From habit they roosted there, even though 

 they knew some enemy to be abroad that had knowledge of 

 their hiding place, and though an innate instinct must have 

 urged them to choose another location. 



I do not pretend to intimate that newly formed habit 

 runs contrary to instinct among all birds and animals, for 

 such is not the case. If it were, there soon would be no ani- 

 mals or birds left, nor other intelligent life. If the weak 

 inoffensive bird in the bush did not instinctively change its 

 abode after that abode had been pillaged, a second outrage 

 from the same source would soon follow. The same prompt- 

 ing causes that bird to change its abode from season to sea- 

 son, for, if the home were permanent, it would not long sur- 

 vive the encroachments of its enemies and, once discovered, 

 would immediately became a prey to repeated maurauding 

 expeditions. On the other hand, there are certain birds, 

 which, because they build in protected localities, have no need 

 to change, and so, season after season, and year after year, 

 return to the same spot to nest. 



To such a class belong the martins. They have been pro- 

 tected for hundreds of generations, first by tree holes and 

 then by the buildings of civilization. The instinct for pro- 

 tective change of home has gradually become dormant and 

 the habit now nearly an instinct, of permanency has be- 

 come dominant, just as the habits of civilization dominate 

 our own savage instincts, which often burst forth in times 

 of crisis. If repeatedly disturbed, the birds will change, 

 often at terrible cost, as has been the case of many of our 

 game birds, ducks and even song birds, and the old instinct 

 of natural preservation against enemies, never really absent 

 only dormant becomes uppermost. They will learn new 

 habits with which to combat most effectively the new enemy 



