A CITY OF BIRDS 59 



right when he described instinct and intelligence as upon 

 divergent tacks of evolution. But the point is that they 

 intertwine, and never more closely than in nidification. 

 Once the nesting site is chosen, then instinct operates upon 

 the ground-plan of intelligence. But if there is a spice of 

 instinct in choosing the site of the nest, so there is a spice 

 of intelligence in building it, since the bird can and does 

 miiet circumstances which break the routine and experi- 

 ment (as sometimes happens) with new materials. It was 

 intelligence, not instinct, which this chaffinch lacked. In 

 prospecting for sites, activity is chiefly unpredictable and 

 indeterminate ; in building upon them, fixed and regulated. 

 Or, to put it in another way, the present trains the 

 cannon, the past charges it (viz, directs the bird how 

 to build its nest), and the present discharges it. Nidi- 

 fication, I am sure, is an example of the most delicate 

 interaction of instinct and intelligence. 



Blackcap and garden-warbler sang almost side by side 

 in the steep wood fronting one angle of the town, the 

 softer and thicker rush of " pettychap's " fairy music 

 contrasting with his congener's " full, deep, sweet, loud, 

 wild pipe," as White described it, while the tremulous 

 sighs of the wood-wrens not so high up among the 

 " melodious greenery " as they get later in the season 

 seemed to express pleasure at the privilege of enjoying 

 these two princely warblers beneath its fresh, bright 

 canopy. It is not often that garden-warbler and 

 blackcap can be heard in close proximity, for the 

 former (it may be) seeks to avoid any critical comparison 

 of his melody with that of his more brilliant cousin. 

 In quality and general likeness there is very little 

 difference between the two songs, though the garden 

 warbler's is more sustained ; in the manner and spirit 

 of delivery the birds are poles apart. The garden- 

 warbler is a more approachable bird — I have watched 

 him singing and flitting about in my sight for half an 

 hour at a time — he sings more frequently, and his lay 

 is of a soberer colouring. In the blackcap's song there 



of the eggs and young to the shingle being, he said, as perfect as 

 that of terns. Here initiative, experiment and intelligence were 

 completely justified of instinct. 



