PARASITIC WEAVERBIRDS 17 



Territorial behavior is reduced to the defense of the nest by both 

 members of the pair. The territory is hmited to the nest and its 

 immediate approach. A strange individual is mobbed if it comes 

 close to the nest, but it is not pursued once it leaves. Territorial 

 defense and aggressiveness are at a maximum during the period of 

 pair formation and incubation. 



Both sexes incubate for short periods at a time during the day, but 

 only the hens stay on the eggs at night. Throughout the duration 

 of incubation and the rearing of the nestlings, the males continue 

 to add straws to the nest. 



To all these rather unusual aspects of the reproductive picture as 

 it exists in tliis species, one more aspect must be added. Not infre- 

 quently whole colonies are abandoned simultaneously by the breeding 

 birds, as if at a signal. The abandonment may happen just after the 

 construction of the nests, or even during the time when nestlings 

 are being reared. In one such abandoned colony tlu'ee-quarters 

 of the nests contained unincubated eggs. 



The reports of the red-billed weaver and of species of bishop birds 

 may be considered as evidence of the unusual ethological background 

 more particularly of the cuckoo finch, Anomalospiza imberbis, than of 

 viduine species. 



About the territorial and mating relations of the nearest relatives 

 of the viduines, the estrildines, most of the observations indicate 

 monogamy as the usual condition. V. G. L. van Someren (1956, 

 p. 478) placed on record dissenting data. He noted two females of 

 Euodice cantans simultaneously involved in the same nest, which held 

 what appeared to be two sets of eggs — one fresh and the other well 

 incubated. Of the partridge finch, Ortygospiza atricoUis, he (p. 481) 

 "often found nests within about six yards of each other. There were 

 two hens, but only one cock. Is the little finch polygamous?" Ob- 

 viously, more observations are needed to answer this question. 



In looking back over the data, I can assume only that mating 

 relations may effectively influence temtorial behavior or may be 

 influenced by it, but that neither of these activities seems to have 

 contributed immediately to the advent of brood parasitism. 



Nest building: This component is the most conspicuous and 

 important one of the series. In related, but self breeding, nonparasitic 

 members of the family, diminution or loss of nest building is expressed 

 in the incidence or frequency of adoption of available nests built by 

 other bhds. This occupation is usually peacefully made in old and 

 abandoned nests, and does not involve seizing them forcibly from 

 their builders, but at times it may involve aggressive action against 

 the builders. At least under conditions of captivity such action may 

 take place. Thus, Parker (1931) wrote that in an aviary, Amadina 



