NO. 9 CASQUED HORNBILLS — KILHAM 4I 



formation takes place. It may have no immediate relation to the breed- 

 ing season. I had three young captives, hand-reared and approxi- 

 mately of the same age, in a cage at Entebbe. Mpanga and Zika were 

 definitely paired before they were 3 months of age. Zika would work 

 through Mpanga's throat feathers as he let his head fall back, then 

 he would do the same for her. The other hornbill, and later a fourth, 

 both males, led independent lives except for roosting. Unnatural 

 conditions undoubtedly favored this early pairing. Young birds, 

 however, do not necessarily pair up when confined together. This was 

 shown by three magpies (Pica pica hudsonia), taken before they left 

 the nest, which I kept in a large cage in the same manner as the horn- 

 bills. They showed no inclination to pair. 



Maintenance of close pair formation demands mutual attentions. 

 When casqued hornbills are perching in different trees, the members 

 of a pair are almost always in communication with each other, some- 

 times only with single notes such as "cak" or "ugh." When together, 

 mutual preening, in which the female may take the lead, is a common 

 activity. This preening about the head and nibbling of feathers under 

 the throat went on regardless of the time of year, I saw it going on 

 at dusk in the pair which roosted in our garden in October and again 

 with the pair in the Botanical Gardens, on the day the female emerged 

 with her young one in March. It took place early in the life of 

 Mpanga and Zika. 



I have interpreted as courtship, activities which bring a pair of 

 hornbills into the rhythm needed for the close cooperation involved 

 in nesting. The lead is taken by the male. He feeds his mate and 

 presents her with sticks and pieces of bark. In addition he becomes 

 noisier in his calls and wailing. Similar activities are not uncommon 

 to the courtship of many groups of birds. The male hornbill also takes 

 the lead in exploring possible nest holes. By his cries and wailings, 

 and his flights back and forth, he tries to induce his mate to look at 

 them. 



Stonor (1937) has given an interesting account of a pair of 

 trumpeter hornbills (Bycanistes buccinator) which attempted to breed 

 in the London Zoological Gardens. Courtship consisted principally 

 of the male feeding the female. She would fly down to the feeding 

 dish, then wait expectantly for him to feed her. Sometimes he would 

 do so. At other times he would swallow the food himself. Then, as 

 if stricken with remorse, when she would fly to a higher perch, he 

 would at once follow to feed her a morsel. Stonor wrote of a "curious 

 ceremony, wherein the female flew up from the ground with food in 

 her beak which she passed to the male, who then returned it to her, 



