THE THRUSH GENUS 381 



It contented itself with adding material to the lining and also to the 

 rim of the structure, thereby increasing its height. 1 A new nest is 

 sometimes built upon an old one. A striking instance of this fact is 

 supplied by the editor of the Zoologist in the year 1862 (p. 566) : he 

 examined an edifice, built by a blackbird in thick ivy on a summer- 

 house, which consisted of eight nests placed one above the other, out 

 of each of which a brood had been reared. That the blackbird does not 

 by any means always use again the same nest or the same site is shown 

 by the well-known case in which an individual of this species made 

 its first nest in ivy on a wall, the second in a yew-tree, the third in an 

 apple-tree against a wall, and, on deserting this, a fourth in a birch- 

 hedge, which, being likewise deserted, was followed by a fifth in a 

 vine trained up the wall of the house. In these nests twenty-five eggs 

 were laid, and fourteen young reared a creditable performance. 2 

 The thrush and mistle-thrush will frequently build fresh nests in the 

 same season. What is the behaviour of the ring-ouzel with respect 

 to its second clutch I have been unable to find out. So far the 

 evidence shows that three species either build new nests or repair 

 the old for their second broods. It may be that the normal course 

 is to repair, but that a bird will build anew, if it feels that the first 

 site has become unsafe owing to discovery or disturbance. But this 

 is mere conjecture. 



Cases of what are known as " dual nests " of Thrushes are occa- 

 sionally reported, that is of nests in which the eggs of two species are 

 laid side by side. But it is not always easy to decide whether the 

 juxtaposition is due to birds or boys. What has the appearance 

 of being a genuine case is one recorded by Miss E. L. Turner 

 in Country Life (May 22, 1909). She found and photographed a 

 hen blackbird sitting on a thrush's nest containing four young 

 blackbirds, and one young thrush. It contained originally three 

 thrush's eggs and four blackbird's. Another similar case is given 

 by Mr. P. G. Ralfe, in his Birds of the Isle of Man, of a black- 



1 See note 3, p. 372. Zoologist, 1848, 2997. 



