WAYS OF NATURE 



act more strongly in one kind than in another, just 

 as reason may act more strongly in one man than in 

 another, or as one animal may have greater speed 

 or courage than another of the same species. It 

 would be hard to find two live creatures, very far up 

 in the scale, exactly alike. A thrush may use much 

 mud in the construction of its nest, or it may use 

 little or none at all ; the oriole may weave strings 

 into its nest, or it may use only dry grasses and 

 horse-hairs ; such cases only show variations in the 

 action of instinct. But if an oriole should build a 

 nest like a robin, or a robin build like a cliff swal- 

 low, that would be a departure from instinct to 

 take note of. 



Some birds show a much higher degree of vari- 

 ability than others ; some species vary much in song, 

 others in nesting and in feeding habits. I have 

 never noticed much variation in the songs of robins, 

 but in their nesting-habits they vary constantly. 

 Thus one nest will be almost destitute of mud, while 

 another will be composed almost mainly of mud; 

 one will have a large mass of dry grass and weeds 

 as its foundation, while the next one will have little 

 or no foundation of the kind. The sites chosen 

 vary still more, ranging from the ground all the 

 way to the tops of trees. I have seen a robin's nest 

 built in the centre of a small box that held a clump 

 of ferns, which stood by the roadside on the top 

 of a low post near a house, and without cover or 

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