78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



but only the individuals of the regularly migratory race responded by 

 becoming restless. This indicated that not only was a predisposition 

 for migratory behavior necessary but that it could be manipulated. 

 What can be manipulated experimentally by the investigator may 

 also be effected out of laboratory conditions by "natural" causes. 



At this point it seems useful to note the results of some recent 

 studies because they correct a concept of migration based too largely 

 on what has been recorded in north-temperate areas of the world. 

 The pattern of migration there, with its easily accepted geographic 

 inferences and correlations, is usually expressed in terms of Pleisto- 

 cene climatic fluctuations. However, Moreau (1951) has shown that 

 bird migration is probably as old as bird flight and that what happened 

 during the Pleistocene in Europe and North America merely deter- 

 mined the geographic details of the migrations of individual species; 

 but not the migratory behavior itself. It is true that most of the 

 major, "best organized" migrations of considerable geographic magni- 

 tude seem to have reflections of Pleistocene events, but we realize that 

 migration may have begun anywhere, anytime, with different groups 

 of birds (Drost, 1950, p. 231). Pleistocene glaciation was not its 

 cause. Moreau (1951) and Mayr and Meise (1930) indicated that 

 migration may have originated in any localities where seasonal food 

 scarcity may have caused some birds to move away seasonally and 

 thus have a better chance of survival. Ostensibly, it would seem that 

 this would be acted upon by natural selection, and in this way migra- 

 tory behavior would become established, with or without any influence 

 of Pleistocene glaciation, and, in some cases, probably was much 

 earlier than Pleistocene in origin. In defense of this argument Moreau 

 (1951, p. 247) cited cases of migration entirely within warm areas, 

 and mentioned among them ". . . the Indian population of the cuckoo, 

 Clamator jacohinus, which travels all the way to East Africa after 

 breeding . . ." 



Cuckoos, as a group, are birds with a great tendency or predisposi- 

 tion toward migration. Many years ago, W. L. Sclater (1906) cal- 

 culated that of the 814 species of birds then known to occur in South 

 Africa, 731 were resident, and only 21 were to be considered as 

 African migrants (as distinguished from European and Asiatic winter 

 visitors), and of these 21 no fewer than 9 were cuckoos. Many years 

 prior to Sclater, Emin Pasha, prior to 1888, (published by Schwein- 

 furth, et al., 1888, p. 392) noted the seasonal wanderings of a number 

 of purely African savannah birds in "Equatoria" (the southern part 

 of the present Sudan and the adjacent area of the Republic of the 

 Congo), among which he mentioned Clamator. 



