90 U.S. NATIONAL MUSEUM BULLETIN 265 



removal is frequent, probably more often present than absent, from 

 the picture. We may mention the case reported by Pringle (1946, pp. 

 368-369), who saw a didric cuckoo leave the nest of a Cape sparrow, 

 Passer melanurus, with one of the sparrow's eggs in its bill. It flew 

 to a nearby tree where it broke the egg shell, ate some of the contents, 

 and dropped the shell fragments to the ground. Pringle kept the nest 

 under daily observation and found that the cuckoo (presumably the 

 same bird) returned the following morning and again the next day, 

 each time removing one sparrow egg and laying one of its own 

 (all three cuckoo eggs so similar as to make it highly probable that 

 they were all from the same hen) . Pringle's description suggests that 

 the egg removing was done by the female didric, not by her mate as 

 Pitman's statement (supra) might lead one to assume. However, 

 Pringle did not specifically state that he observed the second and third 

 egg removal, but only that the first was done by a female cuckoo. 



Ottow and Duve (1965, p. 434) concluded, from Duve's extensive 

 data on didrics parasitic on a colony of red bishops near Johannes- 

 burg, that the adult cuckoo removed eggs of the host only from nests 

 in which there were more than two eggs. Occasionally two host eggs 

 were missing from a nest, which these authors interpreted as implying 

 that a second didric hen was involved in the particular instances. In 

 six nests, each with two didric eggs, four no longer contained any of 

 the bishop eggs. Eggs of the didric were found with one host egg in 17 

 nests, with two host eggs in 26, with three host eggs in 4, and with 

 four host eggs in only a single nest. Duve assumed, but showed no 

 real proof, that the female didric did the actual removal of the eggs. 



In our present study we are looking primarily for evidences of 

 evolutionary change A\ithin the genus Chrysococcyx, and must admit 

 that present data fail to show any progressive, or regressive, alteration 

 in this particular segment of the parasitic behavioral program. It may 

 be that fuller knowledge of all the species will indicate a trend toward 

 greater utilization of egg removal in the behavioral nexus associated 

 with brood parasitism in certain species and less in others. The glossy 

 cuckoos arose from an earlier parasitic stock which already had the 

 habit of removing eggs from the nests of their hosts, and, so far as we 

 may see, they have not altered the expression of this trait. In the 

 European cuckoo, Cuculus canorus, which, in the present state of our 

 knowledge, must serve as a "standard of comparison," the male has 

 not been found to be involved in the removal of eggs from host nests. 

 If Pitman's statement should be found to have general validity, this 

 involvement of the male may shed some light on the particular devel- 

 opment this portion of parasitical behavior has undergone in the glossy 

 cuckoos. 



