12 U.S. NATIONAL MUSEUM BULLETIN 2 65 



The change of this aspect of plumage patterns, associated as it 

 is with the presence of sexually dimorphic plumages in the adults, is 

 a biologically interesting development and merits further discussion 

 here. Ventral barring as a pronounced pattern is found in the young 

 of maculatus and xanthorhynchus and of the four African species, 

 while the young of the Malaysian-Australian species have uniform, 

 unhanded underparts from chin to vent. Conversely, the adult males 

 of the latter group show a well-developed trend for crossbars on the 

 underparts, while all but one (Jlavigularis) of the former group do not. 

 In other words, a fairly basic pattern is associated with immaturity 

 in one group and with maturity in the other. The one western excep- 

 tion, C. Jlavigularis, has the barred pattern on the abdomen in the 

 adult-female plumage, and in this respect it forms a significant link 

 between the two sections of the genus. 



The biological appraisal of the evolutionary significance of ventral 

 barring is difficult to form. While such barring is characteristic of the 

 yoimg of many other cuckoos of the subfamily Cuculinae, such as the 

 various species of Cuculus, Cacomatis, and Cercococcyx, it is absent 

 from others of such genera as Clamator, Scythrops, and Coccyzus. 

 It is, therefore, not necessarily an immature plumage pattern in itself, 

 although there are many bu'ds unrelated to the cuckoos in which the 

 young are banded, spotted, or streaked, while the adults are relatively 

 free of such markings. 



It should be kept in mind that we are discussing here, not an exact 

 replication of a transverse pattern, but a tendency to produce this type 

 of marking. In this connection, the following thoughts might well be 

 mentioned. If, as is widely assumed, the juvenal and immature 

 plumages tend to reflect earlier, more "primitive" phylogenetic stages 

 in the history of a group of species to a greater extent than do the 

 corresponding adult plumages, how are we to understand the reversal 

 of pattern sequence within such a fairly compact group as the glossy 

 cuckoos? One solution of this enigma would be to regard the Asiatic 

 and African species as a genus apart from the Malaysian-Australian 

 ones. This, however, would merely reword the question in terms of 

 two related genera instead of one somewhat divergent group of con- 

 generic species. Also, the plumage patterns oi jlavigularis, as already 

 mentioned, help to bridge the gap. If we were to interpret the presence 

 of strongly barred ventral-plumage pattern in the young as more 

 "ancient" than the absence of such a pattern, we might ask if the 

 Malaysian-Australian species were actually more recent in their 

 origin than the others. Yet this seems most unlikely; we can only 

 conclude that the tendency to produce a barred ventral-plumage 

 pattern in the young was developed at the time that a portion of the 

 ancestral stock began to spread westward to the Asiatic mainland and 



