66 U.S. NATIONAL MUSEUM BULLETIN 2 65 



probably all been laid by one bird which, by inference, was prone to 

 use this one species of fosterer. 



To sum up, we have either no data at all (ruficoUis, meyerii, flavi- 

 gularis) or no usable data {maculatus, xanthorhynchus, cupreus) for 

 half of the species of glossy cuckoos. For the other six species for 

 which some (still uneven and at best meager) , information is available, 

 the only currently permissible interpretation informs us that in all 

 species there seem to be some individuals that are not host specific 

 and others tliat are host specific, and that in some areas all of the 

 individuals have the same host choice, making for a local situation 

 of specific-host specificity. This last statement is true for geographic 

 segments of malayanus and lucidus, and almost so, in some areas, for 

 osculans. As far as the current observational records permit of inter- 

 pretation, individual host specificity is found together witli individual 

 nonhost specificity, in parts of the populations of malayanus, lucidus, 

 osculans, klaas, and caprius. 



This is a rather surprising state of affairs. From the standpoint of 

 the reproductive biology of avian brood parasites, the matter of host 

 specificity would seem to be an important, almost a basic, character- 

 istic, explainable as a result of a prolonged adaptive process under 

 the influence of natural selection. To find that it is subject to geographic, 

 subspecific, and even individual variation shows otherwise. In some 

 parasites, such as the European cuckoo, practically all the individual 

 hens are host specific; in others, such as the brown-headed cowbird 

 the great majority are nonspecific, but in the glossy cuckoos we find 

 all stages within each of several species! Lest the novelty of this 

 situation seem unique, however, one may recall that a similar diversity 

 in another aspect of their total behavior exists m many birds, including 

 some of the glossy cuckoos, namely in their migratory habits, M'here 

 the same species may have highly migratory as well as completely 

 sedentary races and, as in the case of the song sparrow, migTatory 

 and sedentary sympatric individuals. 



Egg morphism 



Inasmuch as adaptive resemblance between the egg shells of brood 

 parasites and those of their regidar hosts is very marked in some 

 instances and inasmuch as this is one of the more obvious areas in 

 which evolutionary adaptation to a parasitic mode of reproduction 

 may be expressed, it is essential that we review the situation — and 

 the evidence behind it — in the various species of glossy cuckoos. 

 Fortunately, the coloration and dimensions of the egg shells are 

 known for 9 of the 12 species, even though our knowledge of some of 

 them is less ample than we might like. 



