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 
roud 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 arobin 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. J 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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