THEORY OF THE ORIGIN OF NESTS. 147 



for so doing. Again, as in the case of the Blackcap, no female 

 was present, the females, as we all know, arriving late. 



One more case — this time a Hedge-Sparrow. The male was 

 hopping along a wall in front of the female, carrying a piece of 

 straw, excited, as far as Hedge-Sparrows can be, shuffling his 

 wings and flirting his tail. But, as Mr. Selous aptly remarks, 

 it is the beginning of everything that is fraught with such signifi- 

 cance. Is this a non-purposive movement springing out of sexual 

 passion, or is it an outward representation of an idea contained 

 in the bird's mind ? 



It appears to me that the fact of the male Blackcap and 

 Whitethroat going through this performance before any females 

 had arrived tends to prove that it belongs to the former hypothesis 

 rather than to the latter, and thereby upholds Mr. Selous' theory 

 that this was the origin of the nest. For, watch a Blackcap on 

 his arrival, or any other male before actually having mated, and 

 you will see that his or their movements point to the fact that all 

 the thoughts are concentrated on the one object — the possession 

 of a female — and to attain this object all their powers, chiefly 

 vocal, are directed. Any thought of the construction of a nest — if 

 really there is at all at this period, which I am inclined to doubt — 

 must be in comparison with the other momentous event in the 

 bird's life wholly insignificant. At no time are the vocal powers 

 of the Blackcap shown to such an advantage as when mating ; his 

 song then is continuous. When not loud it is a low expressive 

 warbling, and if you will watch him you will see that his whole 

 body is trembling with this nervous excitement. At this time 

 also he puts himself in all kinds of curious contortions. I have 

 seen him carry his tail more than at right angles to his body, 

 which he does at no other period of his life. The same thing 

 may also be said of the Whitethroat, only, in his case, warbling 

 would hardly express his nervous vocal production — it is more 

 of an angry scolding. 



Again, the Chiffchaff only floats about the air like a big moth 

 when trying to win a mate. Much the same might be said about 

 the Garden Warbler. 



The Marsh-Warbler produces far more vocal variations at 

 this time. The Red-backed Shrike never mimics to such per- 

 fection as when mating. I have heard in succession Swallow, 



