50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



The situation we have just outlined in Clamator glandarius, es- 

 pecially in Africa south of the Sahara, and in Eudynamis scolopacea 

 in southern Asia, appears, at first glance, to go counter to this idea. 

 However, one important factor that enables their excessively multiple 

 egg deposition to continue as a reasonably well-functioning habit is 

 that both of them use large hosts, mostly birds as large as, or even 

 larger than, themselves, that are capable of incubating successfully 

 more of the eggs and of rearing more of the young of the cuckoos 

 than is the case with other species of cuckoos, regularly parasitic on 

 birds smaller than themselves. In the latter situation one cuckoo 

 egg is often close to the limit of the hatching potential of the host, and 

 in such cases multiple-egg deposition would merely bring about the 

 loss of the nest and its contents. In other words, the fact that in the 

 case of the great-spotted cuckoo and the koel the parasite-host size 

 ratio tends to favor the host has the effect of lessening, if not eliminat- 

 ing, any selective pressure against multiple parasitism. This has made 

 it possible for sub-Saharan glandarius to become established over a 

 vast area. It seems, however, that as the frequency with which it 

 selects smaller birds, such as starlings instead of crows, as fosterers 

 increases, it will again be committing itself to the selective pressure 

 to which it is temporarily fairly immune. 



EGG MORPHISAI 



The great development of egg morphism in Cucidiis canorus, with 

 its connotations of adaptive evolution, could only have come about 

 from a basic wide range of original variations in eggshell coloration. 

 However, this is a highly specialized species, far removed from the 

 situation in the crested cuckoos of the genus Clamator. In fact, the 

 very simplicity of the whole matter of eggshell coloration in Clamator 

 permits some suggestive glimpses into the early stages of a process 

 that has not gone far in this genus, but that has not only advanced, 

 but, in doing so, has obscured its past history, in Cuculus. 



The basic, primitive, unspecialized type of eggshell in the cuckoos, 

 as a family, is unpigmented, unmarked white. In this character the 

 cuckoos agree with the doves, the parrots, the owls, the touracos, and 

 also with the bulk of the scansorial and picarian families. The eggs 

 of the relatively unchanged, nonparasitic cuckoos are either plain 

 white or tinged with plain, unmarked, pale bluish, and this may be 

 looked upon as the original, basic type in all cuckoos. However, 

 numerous kinds of cuckoos lay eggs that are pigmented in a plain, 

 overall tone, and, in the most highly specialized species, we find some 



