38 U.S. NATIONAL MUSEUM BULLETIN 2 65 



of Cuckoo. I have worked this area for 10 years, and although hundreds 

 of Cuckoos have been reared durmg that period, I cannot see that the 

 Sericornis has diminished in numbers. In July and early August 75 

 per cent of the Scrub-Wrens' nests contain one or more eggs of a 

 Cuckoo; later on in the season no Cuckoo eggs are noted. It appears 

 to me that Sericornis . . . rears a brood of its own to keep up their 

 numbers. Sericornis, in my experience, does not resort to the habit 

 of the Blue Wren (Malurus) of embedding the Cuckoos' egg [in the 

 lining material, thus preventing the hatching out of the imposter's 



egg]." 



To turn now to the problem of competition for hosts between the 

 various members of the genus Chrysococcyx, obviously more similar 

 to each other than they are to such different, although closely related 

 genera as Cuculus and Cacomantis, \\q may note that in areas where 

 two or more species of glossy cuckoos are sympatric as breeders there 

 is a considerable overlap in their host lists. Thus, in southern Asia 

 maculatus and xanthorhynchus utilize many of the same fosterers; 

 in Africa caprius and Haas overlap, but on the whole the former is 

 much more prone to use weavers as hosts w^hile the latter uses sun- 

 birds and warblers primarily. The yellow-bellied emerald cuckoo, 

 C. cupreus, is apparently, so far as present knowledge goes, an indis- 

 criminate user of both groups of hosts but also lays often in the nests 

 of a bulbul, which the other two do not. Thus, weavers, Ploceidae, 

 account for 78.5 percent of all host records for caprius and only 

 13 percent for klass, with 35 percent for cupreus; warblers and fly- 

 catchers, Sylviidae, account for only 9.5 percent for caprius as com- 

 pared with 47.5 percent for klass, and with 15 percent for cupreus; 

 sunbu-ds, Nectariniidae, comprise only 5 percent of the host records 

 for caprius, 30 percent for Mass, and 15 percent for cupreus. To these 

 last figures may be added the statement, made orally to me by Pitman, 

 that in his very extensive experience in Uganda he found sunbirds 

 to be the most frequent, almost the "regular," hosts of klass and very 

 se dom of caprius. 



In Australia basalis and lucidus (plagosus) overlap very considerably 

 in their host choices, more than half of their fosterers being parasitized 

 by both species, but they do exhibit some differences in that lucidus is 

 largely given to laying in spherical or domed nests rather than open 

 ones, while basalis uses all types equally. Thornbills of the genus 

 Acanthiza are the most frequently used hosts of lucidus (plagosus), and, 

 while they are often used by basalis as well, the latter cuckoo is more 

 partial to wrens of the genus Malurus. About 30 percent of all host 

 records of lucidus (plagosus) is with species of Acanthiza, in basalis 

 about 15 percent of the records involves thornbills, while Malurus 

 accounts for nearly 30 percent. 



In the pages that follow are enumerated the known hosts of all the 



