BLACKBIRDS, NIGHTINGALES, ETC. 305 



general principles by the female blackbird, and she 

 found it in the spreading network of rootlets, belonging 

 to water-loving plants that grew in little rills and ditches, 

 near about her bosky brakes. But to this, mud clung, 

 and, in consequence, there came to be a good deal of 

 the latter in the cup of the nest. Something must be 

 done with it. She began to daub and press it, and, as 

 she became, gradually, more and more a plasterer, mud 

 seemed more and more the proper sort of material to 

 use, till, at last, she sought it for itself alone, utilising 

 the fibres which bound it together, and which had, at 

 first, been what, alone, she sought, as a means of con- 

 veying it. But when the mud, thus brought, had been 

 thoroughly smoothed and plastered, so that the nest 

 seemed perfect and " a thing complete," like the 

 thrush's, there would still be something more to be 

 done, for she — our hen blackbird — had always been 

 accustomed to work in stages, and the final or grass- 

 thatching stage had not yet been entered upon. There- 

 fore, she would cover up and entirely conceal all her 

 fine plaster-work, so that no one, seeing the finished 

 nest, would imagine that it existed in any part of it. 

 But will she always do this ? I cannot think it, for 

 she is a bird of sprightly intelligence, and I believe 

 that, like the thrush, she will some day find out that 

 the neatly-plastered cup of mud does quite well enough 

 to lay her eggs in, and that the further labour of 

 thatching it with grass can be very well dispensed with. 

 Any saving of time or of labour must be of advantage 

 to a species in the struggle for existence, and those 

 birds who thatched their nests more thinly would be 

 enabled to lay their eggs sooner, and thus rear more 

 offspring. In this way, as well as on the " least action " 

 U 



