AVIAN GENTJS CHRYSOCOCCYX 107 



Egg coloration shows agreement between some closely related 

 species and discordance between others. Thus, the eggs of the related 

 malayanus and lucidus are plain olive-bronze, but in the also closely 

 related basalis they are white, speckled finely with pinkish red; in 

 oscidans they are deep mahogany-reddish; while in Haas and caprius 

 they are variable, the last named species having half a dozen ovo- 

 morphs, varying from unmarked white, pale greenish, pale or darker 

 bluish to any of these colors or even pale, creamy grayish, variously 

 spotted or even blotched with shades of brownish and grayish. 



In size the eggs of the glossy cuckoos are relatively small for the 

 body size of the birds, but they show none of the drastic reduction in 

 size found in the Eiu-opean cuckoo, Cuculus canorus. In many para- 

 sitized nests the Chrysococcyx eggs are somewhat smaller than those of 

 the host species, in others the reverse is the case. Apparently the need 

 for reduction in egg size has been less than in the larger cuckoos that, 

 like Chrysococcyx, use nests of smaU passerine victims. 



As indicated in the present survey and discussion of host selection, 

 host specificity, and egg morphism, the glossy cuckoos as a group have 

 evolved diverse host preferences and have done this to varying degrees 

 of rigidity or intensity, but they have not gone so far as to evolve 

 gentes within any of their species, as has Cuculus canorus. All of the 

 changes described in this paper, all the expansions of the range and 

 variety of host nests utilized, and the contracting specializations 

 within these enlarged choices of hosts, have made it possible for the 

 glossy cuckoos to find relatively noncompetitive niches, as far as their 

 congeners are concerned, and yet to take advantage of a vast passerine 

 fauna in three contments and many oceanic islands. The degree to 

 which sympatric species of Chrysococcyx have become mutually allo- 

 xenic is an indication of evolutionary change; the degree to which 

 they are still homoxenic implies the distance they have still to travel 

 toward a theoretically perfect intraspecific independence and non- 

 competitive coexistence. 



