68 BIRD LIFE GLIMPSES 



leads up to pairing, and I can say positively from my 

 own observation that rooks often pair upon the nest. 

 This is the regular habit with the crested grebes, 

 and I have seen it in operation between them after 

 some, or at least one, of the eggs had been laid — 

 possibly they had all been. But this must surely be 

 to the danger of the eggs, so that, as these birds 

 build several nests, natural selection would favour 

 such of them as used separate ones for pairing and 

 laying. It does not, of course, follow that a ten- 

 dency to make a secondary nest and use it for a 

 secondary purpose would develop itself in any bird 

 that was accustomed to pair or court upon the true 

 one ; but it might in some, and, whenever it did, 

 the evolution of the "run" or "bower" would be 

 but a matter of time, if, indeed, it should not be 

 rather held to exist, as soon as such separation had 

 come about. There would be but a slight line of 

 demarcation, as it appears to me, between an extra 

 nest, which was used for nuptial purposes only, and 

 the so-called bowers of the bower-birds. As for the 

 ornamentation which is such a feature of these latter 

 structures, the degree of it differs amongst them, 

 and we see the same thing — also in varying degrees 

 — in the nest proper. The jackdaw, for instance — 

 and the proclivity has been embalmed in our 

 literature — is fond of putting a ring " midst the 

 sticks and the straw " of his, and shags, as I 

 have noticed, will decorate theirs with flowers, green 

 leaves, and bleached spars or sticks. It seems 

 natural, too, that an aesthetic bird, owning two 

 domiciles, one for domestic duties and the other for 

 love's delights, should decorate the latter, more and 



