POWER TO EXPRESS THOUGHT 27 



denly one of them is overmastered by the nest-building 

 instinct which has hitherto lain dormant. This par- 

 ticular bird is impelled by some irresistible force t6 

 seek out a site and then forthwith to begin to build 

 the nest. The nest-biulding instinct of its mate, which 

 is dormant, is at once awakened by the sight of its 

 spouse collecting material. When this happens the 

 second bird begins collecting, and is content to work 

 at the structure already commenced by its mate. 

 Assuming the correctness of the suggestion that the 

 nest-building instinct does not, as a rule, become 

 awakened simultaneously in a pair of birds, what will 

 happen in the exceptional cases when the instinct does 

 awaken simultaneously ? When this happens, it is my 

 belief that each sex commences to build a separate 

 nest. When one of the pair discovers what its mate 

 is doing, it, of course, gets angry and scolds it. The 

 other returns the compliment. Probably the next step 

 is that each examines the handiwork of the other and 

 thinks very little of it. Possibly at first each refuses 

 to 3aeld to the other, or the one whose nest is the 

 least advanced leaves this in favour of the other, or — 

 a third alternative — the stronger bird may attack the 

 weaker and compel it to desert its nest. 



This, of course, is pure conjecture. But it is in 

 accordance with the fact that numbers of nests are 

 commenced which are never completed, and which, 

 indeed, never progress very far. There are at present 

 in my verandah two nests belonging to bulbuls which 

 have been left after about three hours' work was put 

 into them. Several explanations of this phenomenon 



