AVIAN GENUS CHRYSOCOCCYX 87 



Number of eggs 



The number of eggs laid by one glossy cuckoo in one breeding 

 season is another aspect of their breeding biology on which we still 

 need further information. There are no data, either direct or infer- 

 ential, on any of the Australasian species of these birds. In the case 

 of the African species, klaas, I noted (1949a, p. 137) that one dissected 

 hen had one nearly ripe egg in the oviduct and three much enlarged 

 yolks in the ovary, suggesting that at least four eggs would have been 

 laid by this bird. In the case of caprius, Plowes (1946b, p. 271) found 

 three white eggs of this cuckoo in a smaU colony of masked weaver 

 nests {Ploceus velatus) near Bloemhof, Transvaal, and concluded that, 

 since this is an uncommon egg morph of caprius, aU were probably the 

 product of the same hen, which would thus have laid at least three 

 eggs. In another colony of masked weavers containing 37 nests, I 

 reported (1949a, pp. 158-159) that examination showed that 20 were 

 in use and that of these, 4 each contained one caprius egg. The eggs 

 were all alike in size, color, and markings and were probably all the 

 product of the same hen. In another case, a colony of 28 nests of the 

 same weaver, 3 contained one egg each of the didric, again all alike in 

 color, markings and size. In this case I collected the female didric 

 and "although the bird was badly spoiled by the shot, I could make 

 out with the aid of a hand lens that there were three discharged egg 

 follicles in the ovary. There might, however, have been more but I 

 could not make out any others definitely. . . ." Ottow and Duve 

 (1965, pp. 433-434) concluded from their data that each female didric 

 lays not more than four or five eggs during a breeding period. It is 

 not clear from their paper if by a breeding "period" they mean an 

 annual breeding season or a section of such a season, comparable to a 

 single clutch or to one nesting of a two- or three-brooded bird. Also, 

 as we have seen above in our discussion of egg intervals, there is some 

 reason to ask if this number accurately represents the total. 



Removal of Host Eggs by Adult Cuckoos 



The habit of removing one or more of the hosts' eggs from a nest 

 has been known for a long time in many quite unrelated avian brood 

 parasites, cuckoos of several genera (Cuculus, Clamator, Chrysococ- 

 cyx, Cacomantis, etc.), cowbirds (Molothrus) and widowbirds (Vidua), 

 and possibly honey-guides (Indicator). While the correlation of this 

 habit with a parasitic mode of reproduction seems obvious, the origin 

 of the behavior is still completely unknown. As yet, no one has been 

 able t-o suggest an antecedent behavioral trait that might have been 

 altered into one of removal of eggs from the host's nest by the para- 

 sitic bird. While egg removal by the adult parasite operates to its 



