NO. 9 CASQUED HORNBILLS — KILHAM 5 



the tree, then fly off about 6:45 a.m. They thus spent nearly 12 hours 

 roosting. When I returned from a short safari on October 19, I 

 found that the pair had left. I presumed they had started to nest. 

 Unfortunately, I had not discovered at this time that male hornbills 

 can be identified by the white patch on the bill. I had spent many 

 evenings watching the pair and wondered if they would return. Later 

 I had some evidence that the male continued to roost alone in the 

 Institute Compound. This evidence was most suggestive. On the 

 evening of January 19 I heard a familiar bill whacking outside of 

 my window. A male hornbill was roosting on the same male perch 

 observed early in October. He spent only one night. I now recog- 

 nized, by the white patch on his bill, that he was the same bird I had 

 observed some weeks before roosting in an unusual place just beyond 

 our garden. At night he was perched on a bare limb 20 feet over a 

 driveway. On the nights of January 28 and 29, he was on the same 

 perch, silhouetted against the sky. On the evening of January 31, 

 this hornbill again came to our big tree, alighting first on the female 

 perch, then settling on the male perch. Apparently the lone male 

 alternated roosting places. Although territory among casqued horn- 

 bills was not obvious much beyond the vicinity of the nest tree, it 

 would appear possible that the area used for roosting might be more 

 permanent. This situation would be worth further investigation. My 

 captive hornbills, Mpanga and Zika, became extremely nervous at the 

 approach of the evening. This was true even when in a room with 

 artificial illumination. They appeared to have a strong desire to be 

 on a roost they were used to and where they felt secure. Each bird 

 perched on exactly the same place on the roosting pole night after 

 night. 



Courtship behavior and the pair bond. — Casqued hornbills remain 

 closely paired the year around, as far as I could determine. Some of 

 their activities prior to nesting appeared to be courtship behavior. 

 The pair of hornbills that roosted in our garden from August to Oc- 

 tober could be readily observed. They would come flying in about 

 dusk. Soon after they were perched side by side, the male would 

 jerk his head and pop a cherry-sized fruit to his bill tip. Then he 

 would bend over and try to feed the "cherry" to his mate. Usually 

 she would not accept. This never discouraged his efforts. For ex- 

 ample, on September 18 he hung his head and with a few slight heaves 

 ejected a "cherry" from his gullet. He held it delicately in the tip 

 of his huge bill as he offered it to his mate. She refused. The male 

 then opened his bill with an upward toss which sent the "cherry" fly- 

 ing back into his throat. In a few minutes he again produced the 



