380 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loe 



be recalled that the nest I was watching was destroyed 14 days after 

 the last host's egg was laid and the smashed cuckoo's egg in the nest 

 seemed then about in hatching condition. One of Skead's cases 

 suggested a possible incubation period of 12)^ days, while his second 

 one seemed three days less, and caused him to ask if the cuckoo's 

 egg might begin its development some time prior to ovulation. It 

 would seem unlikely that the incubation period is under 12^ days. 



Evicting Habit 



Our knowledge of the evicting habit in the jacobin cuckoo stiU 

 requires clarification. In 1949 (Friedmann, 1949a, p. 37) I was aware 

 of no real evidence and could only conclude that while the young 

 cuckoo was almost always the sole survivor of a nest, the absence of 

 any of the rightful young might be the result of their failure to compete 

 for food with their parasitic nest-mate rather than that they were 

 actually evicted alive by it. Skead (1951, pp. 172-173) has described 

 an instance in which the nestling jacobin tolerated eggs and young 

 in the nest for up to four days, and another in which it made no 

 attempt to evict eggs for four days but in which a chick of the host 

 was found to disappear within less than a da}^ after hatching (but 

 not necessarily evicted by the cuckoo). In the first case, Skead 

 conmients that, considering how the young cuckoo covered and almost 

 suffocated its nest-mate (a Layard's bulbul), the "possibility of death 

 of nestlings b}^ this means must not be ruled out. The chick was so 

 weak . . . when retrieved . . . that had it remained there much 

 longer, it would have been smothered. Therefore, I wish to draw 

 attention to the suffocation of cuckoo's nest-mates and the possibility 

 of their subsequent removal by the foster-parents during nest-sani- 

 tation . . . ." 



In this connection, an observation by Pike recorded by Godfrey 

 (1939, p. 23) and inadvertently overlooked in my earlier report is of 

 interest. At Butterworth, Transkei, Cape Province, he found a nest 

 of a fiscal shrike on January 15 containing only one egg— a jacobin 

 cuckoo's. On February 27 the nest was revisited and was found to 

 hold a young jacobin and three j^oung shrikes. Still later he saw 

 the four young birds perched on twigs near the nest, and still later 

 he noted that the young shrikes had left but the cuckoo was still 

 being fed by an adult shrike. This is the only definite instance 

 known to me of the nest-mates surviving together with a jacobin 

 cuckoo. From this, and from the two instances described b}' Skead, 

 in which eviction by the cuckoo, if any took place, did not occur for 

 some days after hatching, it follows that evicting is certainly not 

 invariable or immediate, and, for that matter, it is still not possible 

 to say that the young parasite was responsible for any evictions. 



