32 TJ.S. NATIONAL MUSEUM BULLETIN 22 3 



when laying their own, or damage the eggs in the nest at the time. 

 Also the young parasite may, within the first few days after hatching, 

 by aggressive competition or actual eviction, take the place of the 

 normal brood of the host, which one young parasite roughly equals 

 in size and weight. In those parasitic species that are approximately 

 the same size as their hosts, the implication is that the host should 

 be able to raise more than just the young interloper. 



Lack cited the example of the great-spotted cuckoo, Clamator 

 glandarius, the young of which do not "eject the nestling corvids. 

 However, on the argument developed here, the full clutch of the 

 corvid should correspond to its most efficient family-size, so that the 

 addition of even one nestling should upset the balance. It is, there- 

 fore, pleasing to find that the parent Great Spotted Cuckoo removes 

 one egg of the host species when inserting its own." 



The viduines are fairly similar in size and weight to their commonly 

 imposed upon estrildine victims, and they act much like the great- 

 spotted cuckoo. The evidence is still divided as to how consistently 

 egg removal is practised by the laying viduine hen, but that it is 

 frequently done is clear. The case is not, however, as definite as 

 Lack's theory made it out to be. Certainly other parasites, which 

 are hardly larger than their frequently used fosterers, such as the 

 honey-guides (parasitic on barbets of the genera Lybius and Pogon- 

 iulus and the smaller bee eaters of the genus Melittophagus) , and the 

 didric cuckoo (parasitic on various species of Ploceus) usually replace 

 the entire brood of the host with one individual of their own kind. 



Morris (1957, p. 198) found that the parental behavior of the 

 estrildines is fairly uniform, there being no marked differences in the 

 various species that he studied. The incubation period is about 2 

 weeks and is followed by a nestling period of about equal duration, 

 which, in turn, is followed by a period of fledgling dependence on 

 the parents lasting as much as 4 weeks. While we still lack accurate 

 data on these periods for the viduines, it would be strange indeed if 

 they differed greatly from their favored hosts in these respects. 



Antiquity 



The data pertaining to the age of the brood parasitic habit in the 

 weavers has led some writers to a conclusion diametrically opposed 

 to the one presented below. It is only proper to make this point clear 

 at the outset as it shows either that the data are inconclusive as 

 evidence, or that interpretation may influence the appraisal of the 

 known facts. 



While it is generally unwise to carry over evidence and argument 

 from one group of birds and apply them to another, it is necessary to 



