AFRICAN PARASITIC CUCKOOS — FRIEDMANN 389 



The Nestling and Its Development 



When I wrote my earlier account of this cuckoo there were ahnost 

 no data on the giowth and development of the young bird in the nest. 

 Within the next year Hughes (1949, pp. 2-4) filled in part of this gap 

 in our knowledge, while Liversidge (1955) has since filled a good deal 

 more. In addition to these data, there are available some observa- 

 tions kindly supplied me by R. A. Reed. It is from these three com- 

 bined sources that the following description is compiled. 



To begin with the more important items: The duration of the 

 nestling stage (i. e., from the time of hatchmg to leaving the nest) of 

 this cuckoo in nests of the Cape robin-chat was found by Reed to be 

 from 17K to 19 days, by Liversidge to be 20 days ±6 hours, while in 

 the nest watched by Hughes the young cuckoo was found to have been 

 killed by a predator in the nest on its 20th day; one leg, severed from 

 the body, was all that remained. The nestling period for the related 

 European cuckoo, Cuculus canorus, is 20 days, agreeing with the 

 data for the present species. 



On hatching, the young cuckoo is devoid of down and is very dark 

 all over. According to Hughes it is shining black; Reed describes it 

 as dark bluish black; and Liversidge records it as brown, changing 

 within the next two days to purplish brown. The gape at first is 

 yellowish orange with yellowish edges, but becomes wholly bright 

 orange by the end of the second day. The bill is dark horn color 

 with a whitish egg-tooth; the feet are dark flesh color. Liversidge 

 found a day-old chick to weigh 4.9 grams. 



On the fourth day the quill-like, stiff feather sheaths appear on the 

 upper surface of the wings. The next day these sheaths are 3 mm. 

 long and show some black pigment basally; on this day sheaths first 

 appear on the cervical tract. On the sixth day the skin over the eyes 

 begins to open, but only slightly, hardly enough to enable the bird to 

 see. On this day the sheaths begin to show up on the chin, forehead, 

 and sides of the breast, flanks, and abdomen, the longest ones are 

 twice as long as they were on the fifth day, 6 to 7 mm. By the seventh 

 day the cuckoo, now more than four times its natal weight, shows the 

 first sprouting of feathers out of the sheaths on the wings and tail 

 according to Hughes; Liversidge reports this as taking place on the 

 eighth day, and notes that the feathers are grayish with a white 

 terminal bar. On this day sprouting also begins on the sides of the 

 breast, and by the end of the ninth day this condition extends along 

 the entire ventral tract. 



On the 10th day the eyes fully open, a most important change in 

 the development and behavior of the chick. The rest of the plumage 

 breaks from the enclosing sheaths on this day and the next and the 

 bird suddenly becomes quite fluffy, a marked change in appearance. 



