20 General Notes on the Cuckoo. 



currence said to have been actually witnessed by 

 Adolf Miiller, a forester in Darmstadt. Closely 

 connected with the above parasitical habits is the 

 question of the colour of the ^gg. Red or blue 

 specimens have undoubtedly been found in Germany 

 and elsewhere, as well as the typical brown or grey- 

 ish varieties ; but they do not always assimilate to 

 those of the foster parent, albeit to the eggs of 

 Pipits, Wagtails, and so forth, that of a Cuckoo is 

 often exactly similar. The theories advanced to 

 account for this are by no means conclusive, though 

 hereditary habit may afford a clue ; we may, how- 

 ever, be sure that the hen cannot determine the 

 colour of her egg. With it the most usual foster- 

 parents are the Meadow Pipit, Pied Wagtail, Reed 

 Warbler, Hedge Sparrow, and Robin, perhaps in the 

 above order. They seldom, if ever, seem to resent 

 the intrusion, or to notice their consequent losses. 

 The careful observations of Jenner, Hancock, and 

 Mrs. Blackburn show that the young Cuckoo when 

 some thirty hours old begins, unaided, to remove 

 from the nest the rightful progeny or unhatched eggs 

 by means of its broad back, which has a central de- 

 pression for the first twelve days ; but after this 



