124 CUCKO W 



becoming hereditary, it will be seen that it requires but an applica- 

 tion of the principle of " Natural Selection " to shew the probability 

 of this principle operating in the course of time to produce the facts 

 asserted by -^lian, by the anonymous Solognot of the last century, 

 and by Dr. Baldamus and others since. The particular gms of 

 Cuckow which inherited and transmitted the habit of depositing in 

 the nest of any particular species of bird eggs having more or less 

 resemblance to the eggs of that species would prosper most in those 

 members of the gens where the likeness was strongest, and the other 

 members would [cgsteris paribus) in time be eliminated. As already 

 shewn, it is not to be supposed that all species, or even all 

 individuals of a species, are duped with equal ease. The operation 

 of this kind of natural selection would be most needed in those 

 cases where the species are not easily duped, — that is, in those 

 cases which occur the least frequently. Here it is we find it, for 

 observation shews that eggs of the Cuckow deposited in nests of 

 the Red-Backed Shrike (Lanius coUurio), of the Bunting (Emberiza 

 miliaria), of the Redstart (Ruticilla phoenicura), and of the Icterine 

 Warbler approximate in their colouring to eggs of those species — 

 species in whose nests the Cuckow rarely (in comparison with 

 others) deposits eggs. Of species which are more easily duped, 

 such as the Hedge-Sparrow, mention has already been made. 



More or less nearly allied to our Cuckow are many other forms 

 of the genus from various parts of Africa, Asia, and their islands, 

 while one even reaches Australia. How many of these deserve 

 specific recognition will long be a question among ornithologists 

 which need not be discussed here. In some cases the chief differ- 

 ence is said to lie in the diversity of voice — a character only to be 

 appreciated by those acquainted with the living birds, and though 

 of course some regard should be paid to this distinction, the possi- 

 bility of birds using different " dialects " according to the locality 

 they inhabit (see Song) must make it a slender specific diagnostic. 

 All these forms are believed to have essentially the same habits as 

 our Cuckow, and, as regards parasitism, the same is to be said of 

 the large Cuckow of Southern Europe and North Africa, Coccystes 

 glandarius, which victimizes Pies (Pica mauritanica and Cyanopica 

 cooki) and Crows (Corvus corniz). True it is that an instance of this 

 species, commonly known as the Great Spotted Cuckow, having 

 built a nest and hatched its young is on record, but this is a mani- 

 fest error (c/. Salvadori, Uccelli d' Italia, pi. 42) ; the later observa- 

 tions of Dr. A. E. Brehm, Canon Tristram, Stafford Allen, and 

 others leave no doubt on the subject. It is worthy of remark that 

 the eggs of this bird so closely resemble those of one of the Pies in 

 whose nest they have been found, that even expert oologists have 

 been deceived by them, only to discover the truth when tha 

 Cuckow's embryo had been extracted from the supposed Pie's egg. 



