The Zoologist — March, 1873. S435 



remiss on the subject, assuredly our more pains-taking and 

 enquiring German friends have not; and I proceed to produce 

 from the pages of the 'Journal fur Oraithologie' for 1871* some 

 very valuable statistics on a large series of cuckoos' eggs, given by 

 Dr. E. Rey, from specimens in his own collection, all of which were 

 obtained either by himself in the neighbourhood of Halle, or 

 by a friend in Dessau, so that he is able to rely upon his facts as 

 authentic. 



Dr. Rey modestly begins by desiring to contribute a little mite 

 to the history of the propagation of the cuckoo, in connection with 

 the interesting observations of Baldamus and others, and says that 

 "amongst his cuckoos' eggs many are found whose colouring and 

 (foster) parentage speak very much for that theory;" and adds 

 that " amongst these he reckons also the cases where the cuckoo's 

 egg did not indeed occur in a nest of the species whose eggs it 

 resembled in colour, but where a cuckoo's egg was introduced 

 which corresponded with those of some allied and similarly- 

 building species of warbler." t 



The author then goes on to discuss the question of blue and 

 bluish green cuckoo's eggs, eggs of which colour alone (as he 

 affirms) the cuckoo places in the nests of Ruticilla phcenicurus, 

 and while they are also found of this colour in the nests of the 

 hedgesparrow and the whinchat, in the nests of no other birds, to 

 which the cuckoo is accustomed to entrust her eggs, are they ever 

 found ; and this " striking phenomenon," he suggests, can be best 

 explained by accepting the theory of Baldamus. 



There is one more preliminary remark, in reference to the blue 

 cuckoo's eggs, which I cannot forbear to quote, because it advo- 

 cates a principle to which I have often called attention in the pages 

 of the ' Zoologist' and elsewhere, t'/s'., the valuable testimony which 



♦ Pp. 225—228. 



+ It is, pcthaps, worth while to remind my readers, that the argument here, as 

 expressed originally hy Baldamus, is, that though for the most part the cuckoo finds 

 the nest of that species of warbler which it requires for its peculiar circumstances, it 

 will oftentimes happen that it does not find such nests in the necessary numbers, or 

 sufficiently advanced or retarded for its purposes : — " It wiU, therefore, be unable to 

 find for each of its eggs a fitting nest of that species to which it was prepared to 

 entrust it, and to which it was used ; so it finds itself obliged to introduce one and 

 another egg into the nests of some other warblers, if haply by good chance it can do 

 BO. Thus, then, it comes to pass that there are, and according to the nature of 

 circumstances there must be, proportionahly many exceptions oT the rule." 



