40 Life History of Common Cuckoo. 



" The eggs laid in the nests of Ruticilln phcenicurus 

 (redstart) and Fringilla montifringilla (brambUng) are 

 nearly always like those of the nest-owners in colour 

 and markings {57 out of 67 in those of the former, and 

 all in those of the latter). Imitations are also common 

 in nests oi Sylvia cinerea {vfhitethToa.t), Sylvia hortensis 

 (garden-warbler), Acrocephalus streperus (reed warb- 

 ler), and A. phragmitis (sedgewarbler), while they are 

 rare in others, and never yet found in nests of Troglo- 

 dytes parvidus (common wren). Accentor modidaris 

 (hedge sparrow), and the different Phylloscopi (warb- 

 lers). In most countries, it may be said that there 

 are many more cuckoos' eggs which do not imitate 

 those of other birds than there are successful imita- 

 tions." * 



But all this, acute as it looks, removes the difficulty 

 only a step or two further back. If the thing has 

 become a fixed habit or instinct by heredity, then at 

 some point the birds reached a decision on the subject 

 as to which birds could be imposed upon more easily 

 than others ; and one fatal disadvantage pursues this 

 theory that the earlier birds were the most discerning, 



* Mr. E. Hartert wrote to meeting of the British Ornitholo- 

 gists' Club, 2ist February, 1894, to this effect : " The statements 

 of Dr. Rey, in his Altes und Neues aits den Haushalte des Kuc- 

 kucks, are based upon an immense mass of material probably 

 greater than has ever been examined by a single naturalist, and 

 his results are founded upon a long experience. I myself can 

 add no comment." But it needs to be emphatically remarked 

 here that the unlike eggs are so very much more easily noticed 

 than the matched ones, and that several, and not a few, blue 

 eggs have now been found in nests with the blue ones of the 

 accentor, and that matched eggs have been found in the nests of 

 wrens. (See Zoologist, 1895, p. 228). 



