92 U.S. NATIONAL MUSEUM BULLETIN 2 65 



hatched in a red bishop's, Euplectes orix, nest, had a nesthng period 

 of between 19 days, 18 hours, and 22 days. The reason for this uncer- 

 tainty may be seen from the follomng details. On March 4 at 7:15 

 a.m. the nest contained four identical, plain blue eggs, and at 12:15 

 p.m. on March 5, it contained one hatched didric cuckoo and three 

 eggs. At 6:30 a.m. on March 25 the didric cuckoo chick was still 

 present in the nest, but when this nest was examined again at 6:30 

 a.m. on March 26 it was empty and deserted. 



In nests in which the cuckoo eggs hatch several days later than 

 those of the host (i.e., probably nests parasitized after incubation 

 has begun in the host's own eggs), the young parasite is unable to 

 evict the larger, heavier young of its foster-parent. On this point R.A. 

 Reed sent me the following notes, which may be given in toto. 



It is by no means always the didric chick which hatches first 

 when a nest is parasitized by this species. Out of a total of 40 nests 

 which I found parasitized by this cuckoo and a total of 37 which 

 I have found containing the young of this cuckoo, three contained 

 cuckoo chicks considerably younger than their nest mates (the 

 offspring of the host). On February 22, 1955 I found a newly hatched 

 didric chick in the nest of a red bishop together with two red bishop 

 chicks approximately seven days old. When I revisited this nest 

 on March 2 I found the didric chick dead in the bottom of the nest 

 apparently trampled to death by its nest mates. On March 2, 1955 

 I found in the nest of a Cape sparrow not more than 100 yards from 

 the above red bishop nest, a newly hatched didric cuckoo chick 

 together with one addled Cape sparrow egg and a Cape sparrow 

 chick approximately six to seven days old. When I revisited this 

 nest on March 4 the Cape sparrow chick and egg were still present 

 with the cuckoo which was calling fairly loudly for food. Unfortu- 

 nately, on my next visit this nest had been robbed of all its contents. 

 The third case was that of a didric cuckoo chick which I judged to be 

 approximately seven days old (it was quite naked) in a Cape sparrow 

 nest which it shared with three nearly fully-fiedged Cape sparrow 

 chicks .... This didric chick was calling so lustily for food that it 

 could be heard from 15 to 20 yards away. 



From these records it would appear that when the didric chick is 

 hatched several days later than its nest mates it is incapable of evict- 

 ing them and is sometimes reared with them. Yet it appears that if 

 all the eggs in the nest are hatched at about the same time the didric 

 chick evicts the young of the host. As an example I cite a red bishop's 

 nest in which I found one didric cuckoo chick and one red bishop 

 chick both approximately two days old on January 15, 1955. On 

 January 17 when I again visited this nest it contained only a didric 

 cuckoo chick. On another occasion I found a red bishop's nest 



