CUCKOO'S FOSTER-PARENTS AND BOGS '.>:< 

 other instances occur in which there is no resemblance whatever 



between tli. I-L.-L: of iln- cuckoo aiitl that of tin- fostei parent The 

 plate of cuckoos' eggs has been specially arranged to bring out some 

 of these anomalies. Figs. 1, 3, and 0, in which cuckoos' eggs are 

 represented with one egg of the fosterer from the same nest, show 

 remarkable contrasts in colour and general appearance. This is also 

 observable in Figs. 13, 16, 17, 21, 27, and 30, all of which differ widely 

 from typical eggs of the foster-parent 



On the other hand, Figs. 2, 4, 5, 10, and 11, each of which in 

 figured together with a fosterer's egg, show remarkable mimicry, and 

 it is apparent also in Figs. 15, 19, 22, 24, as well as to some extent in 

 some of the other illustrations. It will be noticed that out of the 30 

 cuckoos' eggs figured, 27 are of British origin, while 3 are from various 

 part- of tin- ( 'onlim-iit Tin- first of these < l-'i-. 1 1 > is the historic blue 

 egg obtained by Seebohm in North Brabant in a redstart's nest, 

 from which he extracted the embryo and noticed its zygodactyle feet, 

 thus proving that it was not an unusually large redstart's egg, as had 

 been suggested by some of the more incredulous English collectors. 1 

 Although there is some evidence that this blue type of egg occasionally 

 occurs with us, there appear to be no thoroughly authenticated speci- 

 mens in existence to prove the fact ; while in some parts of the 

 Continent, such as Finland, it is not very rare, and is always found 

 in the nest8 of birds which themselves lay blue eggs. This is the 

 more remarkable in view of the fact that the hedge-sparrow is very 

 frequently adopted as a foster-parent in England. Figs. 15 and 

 22, representing eggs taken from a robin's and a redbacked-shrike's 

 nest respectively, are also noticeable as exhibiting mimicry in the 

 opposite direction red predominating instead of blue. 



An examination of a large series of British taken eggs leads to 

 the following conclusions. In some species (of which the hedge- 

 sparrow, wren, and willow-warbler are perhaps extreme cases) there 

 is practically no attempt at mimicry. In others (of which we may 



1 Cf . Ibit. 1806, p. 180. 



