NO. 4 AVIAN GENUS CLAMATOR — FRIEDMANN 5 



this until later. However, in Egypt and in most of Africa south of 

 the Sahara where there are no magpies, this cuckoo parasitizes crows 

 of several species, and also it lays frequently in the dark, hole nests 

 of starlings. Its eggs show little resemblance to those of these hosts. 



If it could be demonstrated that the egg type of Clamator glandarius 

 had evolved as an adaptation toward the use of magpies as hosts (it 

 is the only species of Clamator laying speckled eggs, which egg type 

 in cuckoos generally is considered an "advancement" from the more 

 primitive unmarked eggs), then it would follow that the geographic 

 spread of this cuckoo to areas where there are no magpies would 

 appear to be a matter involving something akin to a "repudiation" 

 of the specialization it had achieved earlier through natural selection 

 with the magpie as the effective agent. This, if established, would 

 open a rare opportunity to study the biology of a highly adapted 

 species in a new environment where this adaptive excellence no longer 

 is a special advantage, but where it is apparently no critical en- 

 cumbrance with new and nonadapted hosts. 



In attempting to trace the course of the evolution of a group of 

 organisms, or of a habit and its correlated morphological characters, 

 it is a common experience to find that the trend generally is toward a 

 more and more perfected stage of adaptation, eventually reaching a 

 degree of perfection beyond which it cannot, or at least does not, 

 go. From the general to the specialized, from the "good enough to 

 survive" to the obviously advantageously adapted, seems to be the 

 history of case after case. What is unusual is to find a highly adapted 

 evolutionary product apparently departing from the particular set of 

 conditions which its past history appears to have been concerned in 

 meeting more effectively, and carrying with it in its secondary path the 

 primary adaptations no longer needed or especially advantageous to it. 



On the other hand, if it should seem more likely that the great- 

 spotted cuckoo developed its speckled-egg type south of the Sahara, 

 and subsequently spread to Mediterranean areas, where its egg 

 happened to "fit" so well with those of a new host, this would have 

 to be considered as a most unusual instance of preadaptation. It 

 should be kept in mind, however, that the known facts concerning 

 host egg similarity, or mimicry, in parasitic cuckoos generally cannot 

 be explained satisfactorily on the basis of any assumed preadapta- 

 tions, but, on the contrary, indicate the degree to which real adapta- 

 tions in egg coloration have been evolved. 



The situation in the jacobin cuckoo is just the opposite. The seem- 

 ingly similar success of the white-egg laying population with that 



