AVIAN GENUS CHRYSOCOCCYX 63 



much of Australia (C. I. plagosus), for which no fewer than 75 kinds of 

 local hosts are now recorded. It causes one to ask if there are no 

 suitable fosterers other than Gerygone on Bellona, Rennell, Loyalty, 

 and other islands, and it also makes one wonder why no breeding 

 popidations of either lucidus or malayanus have become established 

 in the Solomon Islands or in the Bismarks, where the elsewhere- 

 favorite hosts are to be found. 



3. C. basalis: the number of mere egg records in collections and 

 those mentioned in field observations give the impression that this 

 cuckoo is generally nonspecific in its host selection, with a long list 

 of 100 fosterers reported. However, intensive field studies may reveal 

 trends toward individual host specificities, as the following facts 

 suggest. One egg collector in Australia informed me that he had in 

 his personal collection some 15 sets of eggs, each with a single egg of 

 C. basalis, no less than 9 of which were of the blue wren, Malurus 

 cyaneus, and 7 of which came from one locality, indicating that in 

 that immediate area the basalis hens were more inclined to use the 

 nests of the blue wTen than those of any other potential host species. 

 Furthermore, the large number of instances of blue wren parasitism 

 reported by Barrett (1905, p. 22), Campbell (1901), Cleland (1924, 

 p. 181), de Warren (1926, pp. 78-79), Dickison (1928, p. 151), Dove 

 (1928, p. 224), Givens (1925, p. 28), McGilp (1921, p. 240; 1926, p. 

 278), North (1912), Parsons (1918, p. 145), White (1915, pp. 150-152), 

 and many others have clearly demonstrated that of aU the known 

 fosterers Malurus cyaneus is the favorite host of C. basalis. In the 

 Barrington area of New South Wales, Hyeni (in lift.) thought that as 

 many as 90 percent of aU basalis eggs were laid in nests of the blue 

 wren. Another observation suggestive of individual host specificity 

 in this cuckoo was reported by Cohn (1924, p. 76), who found six 

 nests of the red-capped robin, Petroica goodenovii, each of which had 

 an egg of C. basalis. "From the similarity of the eggs and the fact that 

 I saw only one Cuckoo near these nests, I feel reasonably certain that 

 the same Cuckoo laid all the eggs . . . ." Until further data become 

 available it is unprofitable to attempt any probing interpretations, but 

 the suggestion of specialized host trends is obvious. 



4. C. osculans: no definite observational data on individual hens, 

 but the large number of instances of parasitism on Chthonicola sagittata 

 and the close correspondence between the eggs of this host and those 

 of the cuckoo argue for the existence of frequent individual host 

 specificity on the speckled warbler. The fact that the species C. 

 osculans also parasitizes a number of other birds, even if less frequently, 

 indicates a degree of divergence from a one-host trend that amounts 

 to an absence of host specificity in some individuals of this cuckoo. 



