CONTRADICTIONS 249 



another nest, than to waste their time in efforts 

 which, even if at last successful, would make them 

 the parents of fewer offspring. 



" June \st. — The nest above my window has been 

 built at a great rate, and is now almost finished. 

 Compare this with the very slow building of some 

 martins last year, and with Gilbert White's general 

 statement. There is no finality in natural history, 

 and any one observation may be contradicted by any 

 other. This nest, the day before yesterday, was 

 only just beginning, and now it is almost finished. 

 A layer of half an inch a day, therefore, is quite in- 

 adequate to the result, and so the supposed reason 

 for the slow rate of advance, when the nest is built 

 slowly, falls to the ground.^ Late in the year, the 

 nests do, sometimes, drop — by which I have made 

 acquaintance with the grown young, and the curious 

 parasitic fly upon them — but this, I think, belongs 

 to the chapter of accidents, and is not to be avoided 

 by any art or foresight of the bird. Other nests 

 have now been begun, and these, like all the rest, 

 as far as I can be sure of it, are on the exact sites of 

 so many old ones. What interests me, however, is 

 that, on two of these sites, nests, for some reason, 

 were not built last year, though they were the year 

 before. Possibly they were begun there last year, 

 but destroyed without my knowledge (women and 

 gardeners would do away with birds, between them), 

 in which case no further attempt was made to build 

 there. But this I do not think was the case. The 



1 As, were it the true one, this nest should have done— but did 

 not, as I remember. Instead, it stood firm through the tune of 

 sitting and rearing. 



