AVIAN GENUS CHRYSOCOCCYX 101 



recall that Layard long ago (1875-84, p. 155) quoted Mrs. Barber to 

 the effect that G. caprius in South Africa remained near the nests 

 it parasitized, "watching over" them. This, of course, is not evidence 

 in itself, but it makes one wonder what actual observations Mrs. 

 Barber may have had. 



This leads us to a recently published statement. Ottow and Duve 

 (1965, p. 432), based on the latter's extensive field studies in the 

 Transvaal, concluded that the tendency of C. caprius to feed its own 

 fledged young was sufficiently consistent and well developed to play 

 a role in restricting the size of the breeding territory of each adult 

 didric cuckoo, ethologically attached as it was to the nests from which 

 would emerge its future charges. They thought that this caused a 

 very real limitation on the freedom of movement of the didrics, 

 especially if compared with the unhampered movements of a non- 

 fledgUng-feeder such as Cuculus canorus gularis. However, it is by no 

 means established that the latter cuckoo is not also territorial, and the 

 regularity of fledgling feeding by the didric needs farther quantitative, 

 observational proof. 



Benson and Serventy (1957, pp. 347-349) suggested that feeding of 

 young by the adult cuckoo may be due to the fact that those young 

 were reared by seed-eating fosterers and, in their need for insect food, 

 depended on their own species. This suggestion was answered by a 

 more probable one by Marshall and Moreau to the effect that, as 

 responsiveness to the food-begging calls and movements of the young 

 is still present — even if relatively vestigial — in the adult cuckoos, it 

 may have some survival value for those young reared on seeds and in 

 need of the animal protein of insect food. 



Even if the recrudescence of attentive parental behavior may oc- 

 casionally have some such value for the recipients of it, this value 

 cannot be looked upon as explaining its occurrence. It would seem 

 more to the point to ask if species of fosterers that rear young para- 

 sites on seeds alone might be disadvantageous, or at least ill-adapted, 

 for the cuckoo, and if in time they might be eliminated from its selec- 

 tion of hosts. This line of thought would raise the related question as 

 to whether these particular victims are "normal," regularly used 

 hosts at present or whether they are imposed upon only occasionally. 



The basic, theoretical, biological interest attached to fledgling 

 feeding is that it is a revealing atavism. That it occurs in those cuck- 

 oos that also exhibit a tendency toward courtship feeding serves to 

 stress the similarity in the two behavior patterns. The persistence of 

 food-offering in courtship may well expedite the response to the 

 begging reactions of fledglings and may help to bring into expression 

 what must have been an ancestral habit prior to the advent of para- 

 sitism in the cuckoos. 



