234 Foundations of the RooVs Nest. 



ments. The latter are not large or thick : they are 

 clearty the work of one, or at most two, seasons only ; 

 for it is noticeable that when rooks build at a distance 

 from the centre of population they are some time 

 before they finally decide on a site, abandoning one 

 place after another. But the nests forming the prin- 

 cipal streets are piled up to a considerable height 

 fresh twigs being added every year and are also 

 thick and bulky. The weight of the whole must be 

 a heavy burden to the trees. 



Much skill is shown in the selection of the branches 

 upon which the foundations are laid. In the first 

 place, the branch must fork sufficiently to hold the 

 bottom twigs firmly and to give some side-support. 

 Then it must be a branch more or less vertical, or it 

 would swing with the wind too much up and down as 

 well as to and fro. Thirdly, there should be a clear 

 or nearly clear space above the nest to give easy 

 access, and to afford room for it to increase in size 

 annually. For this reason, perhaps, nests are gen- 

 erally placed near the top or outer sides of the tree, 

 where the boughs are smaller, and every upward ex- 

 tension reaches a clearer place. Fourthly, the bough 

 ought not to be too stiff and firm ; it should yield a 

 little, and sway easily, though only in a small degree, 

 to the breeze. If too stiff, in strong gales the nest 

 runs the risk of being blown clean out of the tree. 

 Fifthly, no other branch must rub against the one 

 bearing the principal weight of the nest, for that 

 would loosen the twigs in time, and dislocate the en- 

 tire structure. Finally, rooks like an adjacent bough 

 on which the bird not actually engaged in incubation 

 can perch and ' caw ' to his mate, and which is also 



