1164 The Zoologist — April, 1868. 



(5). Each hen bird lays but one egg in each nest. 



(6). She lays, as a general rule, only in those nests in which she 



finds eggs of the foster-birds already laid. 

 (7). The same hen bird lays eggs of similar colouring, as a general 



rule, in the nests of the same species only. 

 (8). The exceptions to 4, 5, 6, 7 are comparatively rare. 

 (9). Most of the warblers forsake their nests readily and at the 

 smallest interruption. 

 (iO). They pursue and drive away the cuckoo whenever it comes 



into their neighbourhood. 

 (11). The latter takes advantage of the absence of the parents to 



lay its egg in their nest. 

 (12). She lays her egg on the ground, and carries it in her beak to 

 nests not otherwise accessible, and she even does so when 

 she has the opportunity of laying it in nests perfectly 

 accessible. 

 (13). With that end in view, she even lays aside her customary 



shyness of buildings. 

 (14). One may occasionally find two cuckoo's eggs of different 

 colours in the same nest. 



We conclude from these facts, that — 



(1). Nature must have a special motive in these so many circum- 

 stances thus connected with one another, but so peculiar. 



(2). This motive is plainly to be seen. She will, by means of 

 arrangements originally made by her, ensure and facilitate 

 the preservation of a species otherwise much exposed to 

 danger. 



(3). She attains this motive by a very simple method, in that she 

 invests every hen bird with the faculty of laying eggs 

 coloured exactly like the eggs of the bird of whose nest she 

 prefers to make use, according to the locality;* or, in other 

 words, every hen cuckoo lays eggs only of a fixed colour, 

 corresponding (as a general rule) with the eggs of that 

 warbler in whose nest she lays them, and she only lays in 

 other nests when, at her time for laying [" legereife"], one 



* One cannot here make the objection, that so nothing at all is attained : if the 

 foster-mother has only accepted the first, and sat upon the strange egg, then the 

 instinct of becoming foster-parents, so preeminently strong in birds, will provide for 

 the further breeding up of the young. 



