14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



the small differences in the eggs. Mountfort and Ferguson-Lees 

 found that as many as three cuckoos laid in one nest. 



The various topics of interest in the brood parasitism of Clamator 

 are discussed in detail below (pages 14 to 62). 



HOST SELECTION AND ITS EVOLUTION 



A study of the four species of Clamator yields considerable data 

 relevant to the evolutionary changes that formed their present host 

 preferences. Not only are the hosts of each fairly definitely restricted 

 in kind, but two of the four parasites show unmistakable signs of 

 changes in their selection of favored fosterers. To this extent they 

 afford glimpses of the past development of their host orientation, a 

 basic part of their parasitic mode of reproduction. The two that 

 show these signs of evolutionary change are C. jacobinus and C. 

 glandarius, the most primitive and the most advanced members of the 

 genus. In both species, the change took place together with extensive 

 geographic expansion of their ranges. Furthermore, on the basis of 

 the total survey it is possible to sense the course of host selection in 

 the other two Clamators as well. 



Clamator jacobinus (figs. 4, 5, pp. 15, 16) 



The presumed ancestral home of the pied cuckoo, C. jacobinus, 

 is in southeastern Africa, the area now inhabited by the race serratus. 

 In this region, ranging from Cape Province, Natal, Transvaal, 

 Orange Free State, parts of South-West Africa, and Bechuanaland, 

 to Southern and Northern Rhodesia and Nyasaland, the cuckoo has 

 been found to lay its eggs in the nests of 22 species, but 13 of these 

 have been recorded as hosts but once, and 2 others but twice. The 

 only species definitely known to be frequent and regular fosterers are 

 four species of bulbuls of the genus Pycnonotus (nigricans, barbatus, 

 capensis, and importunus) and two shrikes, Lanius collaris and 

 Telophorus zeylonus. These 6 hosts account for 101 of the total 123 

 cases of parasitism by serratus known to me. 



When the pied cuckoo began its geographic expansion, giving rise 

 to the race pica in equatorial and northeastern Africa and in India, 

 the population inhabiting these new areas turned from bulbuls and 

 shrikes to babblers as their chief fosterers. The race pica has been 

 found to parasitize some 36 species of birds, half of which have been 

 so recorded but a single time. No fewer than 26 of the known hosts 

 are babblers, and all the hosts for which there are 5 or more records 

 are species of this group. More than four-fifths of all instances of 



