AVIAN GENUS CHRYSOCOCCYX 113 



This is especially significant in the case of plagosus and basalis, as these species 

 are superficially fairly similar, and it points to the existence of very effective 

 isolating mechanisms. In the absence of personal field experience with these two 

 Australian cuckoos, I cannot evaluate accurately the potential ethological barriers 

 from the published accounts of their vocalisms, posturings, and so forth, but it 

 may be assumed that it is here that the restriction of random mating is controlled. 

 Mayr (1963, pp. 95-107) has brought together from many groups of animals data 

 which show that differences in behavior which may seem slight to human eyes 

 may be all important in this respect. He concluded that, if one were to estimate 

 the relative importance of the various isolating mechanisms, behavioral isolation 

 would head the list. 



Cuckoos as a family appear to be remarkably free from hybridization. In her 

 1958 compilation of known avian hybrids A. P. Gray listed none for any members 

 of the family. Subsequently Parkes (1965, pp. 94-95) has reported only one 

 instance of crossing between two species of terrestrial, sedentary coucals, Centropus 

 viridis and Centropus bengalensis, in Luzon. The absence of any such records 

 in the other, more arboreal and more active cuckoos, suggests that specific differ- 

 ences in appearance, vocalisms, and behavior are constantly effective in their 

 role of isolating mechanisms. 



2. The plumages of Chrysococcyx flavigularis 



Although this report is not intended to include detailed plumage descriptions 

 of the well-known species of glossy cuckoos, in this case it may be useful to have 

 such an inclusion. The following description is based on that of Reichenow 

 (1902, p. 100), with modifications due to other material seen and with the addition 

 of Chapin's notes (1939, pp. 199-201). 



Adult male: upper parts glossy bronze to copper-red, according to Reichenow 

 and Shelley, but dark, glossy bronze-green in the material I have examined 

 personally; the two inedian rectrices dark purplish coppery color, darkest on the 

 middle portion and at the end, the next pair similar on the inner web but yellowish- 

 white to white on the outer web, except for a coppery-bronze band near the tip 

 and also on the basal portion of the feathers, with a white tip; the remaining 

 rectrices white with interrupted dusky bronze subterminal bands and similar 

 bases, the outermost rectrix almost entirely white; remiges dark brown, barred 

 incompletely with whitish or pale buffy on the inner webs; chin and middle of 

 throat and breast bright yellow, bordered with bright, dark glossy green (like the 

 top and sides of the head) ; posterior underparts of body and the under wing 

 coverts pale cinnamon-buff with narrow, somewhat wavy bars of dusky earth- 

 brown, some of these bars with a faint bronze sheen, the interspaces between 

 the bars a little more than one and a half times as broad as the bars; under tail 

 coverts similar but the dusky bars more widely separated; iris dull chrome-yellow, 

 edge of eyelids light yellowish-green; bill dull greenish-yellow, base of the maxilla 

 blackish; feet dull yeilowish-green, claws black; wing 91.5-100; tail 70-80; culmen 

 from base 17-18; tarsus 14 mm. 



Adult female: top of head dark bronze-green with fine, whitish transverse 

 vermiculations on the forehead, sides of crown, and sides of occiput — occasionally 

 these fine markings extend right across the crown and occiput and hind neck; 

 nape, back, scapulars, upper wing coverts, rump, and upper tail coverts dark 

 glossy bronze-green, sometimes with a slightly lighter, more golden, tinge; the 

 lesser and median upper wing coverts with narrow cinnamon tips and widely 

 spaced narrow bars of the same; remiges fuscous, with a faint bronze sheen, 



