AVIAN GENUS CHRYSOCOCCYX 97 



third day when it ousted its nest-mates. On the other hand, Reed 

 (1953, pp. 138-140) reported that a nest of Euplectes orix contained 

 one chick and two eggs of the bishop bird when a didric egg in the 

 nest hatched; four days later the nest was found to contain three 

 young bishops and the young didric cuckoo, indicating that no evic- 

 tion had transpired. In another nest of a red bishop Reed found only 

 a young caprius about foiu* days old. He then put two Euplectes eggs 

 in the nest, and 4)4 hours later both were out of the nest. This sug- 

 gests that the evicting habit persisted until the didric's fourth day at 

 the least. Notwithstanding the apparent absence of eviction in the 

 first case reported, Reed concluded that the nesthng caprius "appears 

 to eject the eggs or young of its host in all cases because in no single 

 instance were large Didric Cuckoo chicks found with Red Bishop 

 young in the same nest , . . ." 



Hunter (1961, pp. 55-63) concluded that the young cuckoo was 

 unable to eject chicks of the masked weaver, Ploceus velatus, if it 

 hatched too long after they did. Unfortunately, no more explicit time 

 was given, but it would seem to be a matter determined by the size 

 and weight of the Ploceus cliicks, plus their increased ability to with- 

 stand the actions of the would-be evictor. 



The young of normal, self-breeding birds are often crowded in the 

 nest and cannot help but push against each other, although they 

 make no attempt to evict. Furthermore, the crowding usually comes 

 later when the young are larger, and since the evicting habit of the 

 young cuckoo is restricted to the first few days, before the nest is 

 really crowded, it follows that it is not a result of crowding but is 

 merely a contact reaction. 



We know that the young of some parasitic cuckoos, such as the 

 crested cuckoos, Clamator, and koels, Eudynamis, do not practice 

 eviction and that in the nests on which they are reared crowding often 

 is very great. We know also that parasitic vddowbirds, Vidua, and 

 cowbirds, Molothrus, do not have the evicting habit, although not 

 infrequently the host young are stai'ved out by the parasite and then- 

 dead bodies removed by their own parents. 



The nest-mate evicting habit reveals no alteration in the glossy 

 cuckoos; it is apparently a trait that was ah-eady present in the stock 

 from wliich they evolved, and, as far as present observations go, they 

 have neither added to, nor subtracted any featiu^es from, its mode of 

 expression. In some Ploceine nests it is often difficult for the young 

 didrics to evict their nest-mates, yet species of Ploceus with domed 

 nests with tubular entrances are among the commonest victims of 

 caprius. Similarly, the nests of many of the sunbirds used frequently 

 by klaas present difficulties for the would-be evictor as they are often 

 deep, frail, pouchlike structures. It might be said ot the glossy 



