PARASITIC WEAVERBIRDS 13 



plumage, and on present knowledge it seems that it may fit into the 

 picture not far from them. Its choice of brood liosts, all grass warblers, 

 gives no clue in this regard, but the fact that its juvcnal plumage is 

 streaky, quite "sparrowy," agrees with the Eapledes group fairly 

 well. The curious presence of a spina interna on the sternum suggests 

 that the cuckoo finch is not a typical ploceid, but I cannot imagine 

 where else to place it. In the character of its sternal spine it recalls 

 such genera as Bvbalomis and Dinemellia, but in no other respects 

 does it seem related especiaUy to them. 



Boetticher (1952, p. 8) placed the cuckoo finch in a separate sub- 

 family, the Anomalospizinae, but there seems to be no need for this 

 arrangement, and in fact no reasons were given. He placed tliis 

 subfamily in a linear list between the Amblyospizinae and the 

 Estrildinae, 



Ethological Background 



Behavior as well as systematic relations must be studied from the 

 same general approach of phjdetic descent. Concerning the behavior 

 of brood parasites, it is important to survey variational trends particu- 

 larly in breeding behavior in the various sections of the v/hole familj^ 

 to which the parasites belong and especially in the groups most closely 

 related and most probably antecedent to the parasites. We must 

 understand what may be termed the psychobiological background 

 from which the parasitic mode of reproduction developed. Without 

 such an understanding it is difficult to formulate the phyletic homol- 

 ogies in behavior essential for a better understanding of the results 

 now visible in the life histories of the brood parasities. 



I made a start on such a survey some years ago (Friedmann, 1950), 

 and to avoid needless duplication, I want to start here with some of the 

 conclusions arrived at in the earlier study. As we saw in the previous 

 section, the Vidiiinae are somewhat intermediate between the typical 

 weavers, Ploceinae, and the waxbills, Estrildinae, but are more 

 closely allied to the latter group. In many species of ploceines and 

 also in many of the estrUdines: 



The hens breed in nests, the actual construction of which has been foreign to 

 their experience and their efforts; in many forms of the latter group, and at least 

 some members of the former subfamily, the care of the eggs is taken over, at least 

 in part, by the cocks. 



The parasitic mode of reproduction occurs ... in five widely separated and 

 quite unrelated families of birds . . . and it is not without , . . suggestive value 

 that this highly aberrant reproduction pattern has developed among the small 

 passerine birds ... in those two families some of whose members have carried 

 the habit of nest-building to its highest and most complex development. It is all the 

 more noteworthy that in the weaverbirds . , . the parasitic habit has developed 

 in two subfamilies, apparently independentlj'^ — the cuckoo finch, Anomalospiza 

 imherhis, in the Ploceinae, and in the members of the Viduinae. . . . Many more 

 details have still to be learned of the annual cycle of behavior patterns in these 



