NO. 4 AVIAN GENUS CLAMATOR — FRIEDMANN 73 



of serratus. However, Strickland (1850, p. 219) was aware of the 

 difference, and commented that to his knowledge this ". . . Cape bird 

 has never before, I believe, been obtained to the north of the equator 

 . . ." Certainly the November bird from Gabon, in very fresh plum- 

 age, cannot have been a migrant from southeastern Africa, where 

 at that time of the year serratus is breeding. Furthermore, the Kulme 

 and Lake Tchad birds, taken in July, and the June specimen from 

 Sagon River, are all in the same stage of molt as Natal birds are in 

 February. This indicates that whether they were resident in the areas 

 of capture, or whether they wandered there from elsewhere, they may 

 not have come from southeastern Africa, where the molting season 

 differs by a third to a fourth of a year from theirs. 



The ranges of the melanistic phases of C. jacohinus and C. levail- 

 lantii are not readily expressed in terms of vegetational areas. Thus, 

 if we take Keay's 1959 Oxford "Vegetation Map of Africa south of 

 the Tropic of Cancer," we find that the black-plumaged C. /. serratus 

 overlaps in its breeding range, the "Relatively Dry Woodlands and 

 Savannas" (characterized by savannas of tall grass with Acacias as 

 well as other trees) and the "Temperate and Subtropical Grassland" 

 (pure grassland above 3,500 feet). The melanistic phase of C. 

 levaillantii appears to be contained within, but is not coextensive 

 with, the "Coastal Forest Mosaic" area. 



To clarify the recorded data, it may be stated at this point that 

 the old report of a black -phase serratus from Denkera, Fantee, Ghana, 

 listed by a number of authors in their compilations, is based on an 

 error. The actual specimen involved, examined by me in London in 

 1962, is not a Clamator at all, but a black cuckoo, Cuculus cafer. 

 Similarly, the supposed record of melanistic serratus from Lamu, 

 Kenya, cited by several writers on east African birds, is actually 

 based on an example of the black phase of C levaillantii, to which it is 

 properly referred in the present study. 



To return to Ford's illuminating appraisal of the whole question of 

 polymorphism, it appears that the situation in the two species of 

 Clamator fits the definition of what he terms neutral polymorphism. 

 It may be explained that Ford distinguishes three types — transient, 

 neutral, and balanced polymorphism. The first is, as its name sug- 

 gests, a polymorphism in the process of spreading through a popula- 

 tion, but once it becomes fixed and ceases to spread it is no longer 

 to be termed transient, but becomes either neutral or balanced. When 

 a variant phase, or morph, has a selective advantage only as long as 

 it does not dominate numerically the total population in which it 



