PARASITIC WEAVE RBIRDS 21 



containing five eggs of the builder and two larger eggs tliat were 

 similarly unmarked white in color but that obviously belonged to 

 another species. No species of viduines occurred in the area, which 

 was under close and prolonged observation by the collector. Judging 

 from his notes, and from the elhnination of unlikely species (on the 

 basis of local ecological notes), I assume that the larger eggs were those 

 of either Granatina or Estrilda. 



Another case was reported by Cliapin (1954, p. 535), who wrote 

 that in Natal, J. Vincent found four eggs of Estrilda subjlava clarkei 

 in a nest with two eggs of Coliuspasser ardens. V. G. Jj. van Someren 

 inform^ed me (in litt.) that in Euodice cantans occasionally more than 

 one female may lay in the same nest. He has records of three simul- 

 taneous clutches in the same nest, represented by nestling birds, well- 

 advanced embr^'os, and nearly fresh eggs. He also has similar records 

 for the cut-throat finch, Amadina fasciata. 



As in nest building, we find much variability in incubation, the sort 

 of variability that if not necessarily conducive to, at least imposed no 

 obstacles in the way of, complete elimination of incubation as is 

 characteristic of brood parasitism. 



The tendency to incubate and to brood is hormonally controlled in 

 doves and in poultry, and probably this condition is also true of other 

 birds. Of species of weavers that often breed in adopted nests built 

 by other birds, variability in broodiness and incubation behavior 

 may also be associated with an underlying endocrine imbalance. If 

 found to be true, the occurrence of an endocrine imbalance would be 

 a "critical point" in the antecedent reproductive pattern — 'the point 

 at which the parasitic mode of breeding began. 



Care and feeding of nestlings: We have here essentially the 

 same pictm-e as we found in the survey of incubation. Both parents 

 are known to feed the 3^oung in the nest in Quelea qveha and in many 

 species of Ploceus — bicolor, capensis, cucullatus, nigerrimus , ocidarius, 

 pelzelni, philippinus, and reichenowi. The female alone feeds the 

 nestlings in species of Eupledes — orix and hordeacea — and in several 

 species of Ploceus — aureoflavus, bojeri, jacksoni, rubiginosus, and 

 velatus. 



Greater variability probably exists in nestling feeding than in egg 

 incubation since nestling birds, wliich are capable of movement and 

 vocalization, are more effective stimuli on the beha^'ior of the adults 

 than are such quiescent objects as eggs. I note that in captivit}' 

 even such an habitual parasite (in the wild state) as a combassou, 

 was known to indulge in attentive behavior, even to the point of 

 raising a brood of young. 



Because of its variable nature, nestling care offers less of a clue 

 about the advent of brood parasitism that do uest buUding and incu- 



526526—60 3 



