NO. 9 CASQUED HORNBILLS — KILHAM 2/ 



Since this episode took place early in the nesting period, I conjectured 

 that the foreign pair had, perhaps, not found a suitable nesting site 

 and the female was trying to take possession of one already occupied. 

 A second episode was difficult to interpret. It took place late in the 

 nesting period, on January 23. I saw a foreign pair fly into the tree 

 containing nest 15. The male repeatedly bent over the nest rim and 

 there was a rattling of bills. He produced a "cherry" at his bill tip. 

 Then he either gave it to the nesting female or dropped it into her 

 nest. The female rattled her bill at the strange male. Ten minutes 

 later the foreign female swung dramatically on a long tangle of 

 epiphytic roots, then landed on the nest rim. This was the only time 

 I ever saw a pair of foreign hornbills perched together on a nest. 

 The intruding female waggled her bill vigorously in the opening. 

 A few minutes later the owning male swooped in and drove the in- 

 truders away. He fed his mate some yellow fruit. She now screamed 

 repeatedly. 



On one occasion I saw a lone male attacking a nest. This was on 

 November 21 at nest 6 in Mpanga Forest. The foreign male came 

 quietly to a limb above the nest, then dropped to the nest rim. He 

 appeared wary, bending his head to one side, then to the other, as he 

 hung his head down to look through the entrance. The female had 

 her bill ready but made no noise. He finally struck at the cement, then 

 sparred with the female within the nest through the opening. I could 

 hear their bills clashing. After 12 minutes the returning male owner 

 drove the trespasser away. He had a leaf in his bill tip which he gave 

 to his mate along with some fruit. It should be mentioned that a male 

 may attack his own nest. At midmorning on November 28 the male 

 from nest 7 flew down and rattled his bill in the opening. He was 

 apparently in a bellicose mood for he next flew to a limb directly 

 over my head, which was unusual. I could see his bill markings 

 clearly. Meanwhile, his mate rattled her bill in the entrance. 



Lone females were the most frequent intruders at hornbill nests. 

 I often saw one at nest 11. She had a favorite perch 10 feet from 

 the entrance where she would sit for some periods. The nesting 

 female would rattle her bill and scream repeatedly, but her mate, on 

 feeding visits, paid little attention to the intruder. On December 12 

 a foreign female perched calmly on the bole above nest 6. She repeat- 

 edly leaned down into the opening, giving the feeding chuckle eight 

 times as she did so. The female in the nest rattled her bill. After 

 15 minutes the male returned and drove the foreign female away. A 

 final and most unusual case of interference occurred at nest 16, which 

 was 30 feet above the ground. On January 30 we had placed some 



