118 BIRDS OF THE COUNTRYSIDE 



hear the cries of the rushing, winged travellers drifted 

 upon one from the well of darkness is to be pene- 

 trated not only by the unsolved mystery of migra- 

 tion, but the sublime miracle of all life, until the 

 whole being responds. Thus do we pass onward from 

 the darkness of birth into the darkness of life and death, 

 speeding forward, and unknowing why we travel, w r hat 

 we pass, and whither we go, guided only by the spiritual 

 stars within the firmament of night. 



One curious nesting phenomenon I must not omit. 

 I have found half a dozen thrushes' nests built on 

 the terminal branches of large trees, fifteen and twenty 

 feet above the ground. This must be the result 



(1) of the few suitable nesting sites hereabouts, and 



(2) of their nests being invariably destroyed. Now, 

 if the birds brought off their young safely by this 

 new fashion, the variation would be seized upon by 

 natural selection and perfected into semi-automatic in- 

 stinct, and the bush-building habits of town-thrushes 

 would entirely disappear. The change is as revolutionary 

 as if special conditions made it necessary for a certain 

 village to build its houses underground. Darwin gives 

 some interesting nesting variations in his posthumous 

 chapter on " Instinct," and they are examples of what 

 Romanes calls " plasticity of instinct." I prefer to 

 call them examples of intelligence by which hereditary 

 instincts are not only modified, but discarded by the 

 associations and circumstances of the individuals of a 

 species. 



Thus impoverished by the departure of the birds, 

 we listen for the first songs of our resident birds 

 with an intentness sharper than in the country, and 

 when we hear them, familiar songs from familiar 

 birds, it is with a satisfaction not achieved by 

 countryfolk with their nightingales, just as light seen 

 through a chink may set the emotions vibrating more 

 than the whole visible day. 



Of late years, I personally could not feel in accord 

 with the throstle's song, which, intermittent with us 

 Londoners in a mild winter (I have heard it all 

 months except August), breaks into its full volume of 



