58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



It should be kept in mind that even with its longer incubation of 14 

 days, glandarius averaged 3 to 4 days less in its incubation period than 

 the magpie hosts it used in Spain, where Mountfort studied it. This 

 would be true for its other corvine hosts as well. It may be that 

 the greater size of glandarius, as compared with jacohinus is reflected 

 in its longer incubation period, but this is by no means established. 

 The incubation periods of the various hosts — shrikes, bulbuls, and 

 babblers — that are used by jacohinus are shorter than those of the 

 magpies and crows used by glandarius. It may be that the change 

 in host choice in the latter offset any advantage that more rapid 

 embryonic development might otherwise have given it. 



HOST-PARASITE NESTLING RELATIONSHIPS 



The development of brood parasitism in Clamator has not included 

 the development of eviction by the newly hatched young. 



In some parasitic cuckoos, notably those of the genus Ciiculus, the 

 newly hatched bird, while still featherless and with still unopened 

 eyes, evicts from the nest in which it finds itself other nestlings and 

 eggs. This it does by pushing against them and slowly burrowing 

 under them until it gets them on its back, when it climbs slowly to 

 the rim of the nest, where with a final and violent, muscular effort it 

 heaves them out of the nest. Thereupon, it falls back into the nest, 

 where it rests momentarily before tackling the next nestmate. This 

 evicting behavior usually lasts only until the fourth day of life, after 

 which the nestling cuckoo tolerates anything that may be in the nest 

 with it. 



This highly peculiar, and obviously instinctive, behavior is one of 

 the features associated with brood parasitism that has not been de- 

 veloped by the species of Clamator. In C. glandarius and C. coro- 

 mandus we have ample numbers of observations to be able to state 

 that usually eviction by the newly hatched cuckoo does not take place. 

 In glandarius, the elimination of the host young that often happens is 

 due to their being either starved or smothered by their parasitic nest- 

 mates, and their dead bodies removed by their own parents. Thus, 

 Mountfort (1958, pp. 54-56) wrote that in only one magpie nest in 

 Spain did he find young of the host and of the great-spotted cuckoo 

 together, and this was only for a very brief period, as the nestling 

 magpie was gone 2 days later. It had hatched 3 days after the eggs 

 of the parasite, and the emerging nestling was never able to overcome 

 this disadvantage. Mountfort concluded that the shorter incubation 

 period of the cuckoo (shorter by 3 days) doomed the young magpie, 



