2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



the African landscape and the African avifauna in such a way as 

 to avoid undue host competition among themselves . . . ."In the 

 present paper I am concerned with three of these cuckoos, all of 

 which occur together in many parts of the continent and on which 

 we have much more information than was available 20 years ago. 



In the prolonged task of amassing egg record data, I have been 

 helped by several collectors and observers who have generously sent 

 me unpublished data. Due thanks for their contributions are here 

 given to R. I. G. Attwell, G. Duve, B. V. Neuby-Varty, G. Symons, 

 V. G. L. van Someren, and C. Vernon. 



The red-chested cuckoo, Cuculus solitarius, is by far the best 

 known of all the African species of its genus. The black cuckoo, C. 

 clamosus, is becoming more adequately imderstood although its 

 suggestive and yet puzzling plumages (the so-called mabirae, jacksoni, 

 and gabonensis entities) are still awaiting satisfactory clarification. 

 The third member of the genus, C. canorus gularis, the yellow-billed 

 cuckoo, is the least often observed and, hence, the least fully docu- 

 mented. Enough is now known of the egg morphism and of the host 

 selection of each of these species, however, to be able to make some 

 meaningful comparisons. 



For the first species, there are now available to me data on 134 

 instances of its parasitism involving some 39 species of hosts (or 

 45 kinds of birds if we list subspecies as well). These data give a good 

 picture of the range and of the frequency of host choice by the red- 

 chested cuckoo. Of the 39 species of hosts, 20, or 51.3 percent, are 

 thrushes, but the percentage of the total number of records of para- 

 sitism that involve thrushes as hosts is even higher — 69 percent, or 

 93 out of the total 134 records. 



For Cuculus clamosus, we now have information on 39 cases of 

 its parasitism involving 16 species of hosts (or 21 if we include sub- 

 species). Of these, 26 instances, or 66.6 percent of the total, involve 

 seven species of shrikes. On the other hand, only three species of 

 thrushes have been noted as victims of the black cuckoo, and for two 

 of these there is as yet but a single record — and only two records for 

 the third species. 



The data for Cuculus canorus gularis are much less adequate: 14 

 definite and 3 indefinite records, involving 7 definite and 3 indefinite 

 host species. Of the definite records, 8, or 57 percent, involve three 

 species of shrikes; 3 involve one species of drongo; 1 each involve 

 single species of bulbuls, starlings, thrushes, and weaver finches; while 

 the 3 indefinite instances involve one shrike and two kinds of thrushes. 



In the present paper I list the currently known hosts of each of 

 these cuckoos and also describe their egg morphism in order to deter- 

 mine what, if any, host egg adaptations may have evolved. In con- 



