NO. 9 CASQUED HORNBILLS — KILIIAM 39 



tenance of the pair bond. This is a matter of interpretation. Ranger 

 uses other phraseology, but the activities he describes are similar. For 

 example, he wrote of the following behavior as having taken place 

 26 days before final entry. "Investigation of a knocking and rat- 

 tling near Site I disclosed the hornbill pair, one striking its bill 

 with vibratory rapidity against a branch. The side of the terminal 

 part of the bill was used, and the point, vibrating, traveled around the 

 surface of the branch till in turn the opposite side came into play 

 . . . then the other bird . . . became enlivened and extending its 

 bill performed the same rattling action." Ranger believed this rattling 

 was the same motion employed in plastering and made special note 

 that both sexes were involved. I am not sure whether this perform- 

 ance is entirely related to the onset of nesting in Bycanistes. My 

 captives, Mpanga and Zika, do a good deal of tapping. They began 

 when 9 to lo months of age and sometimes do it against my clothes. 

 Ranger has stated further that his crowned hornbills made increasing 

 visits to the nest tree as the season progressed. Such flights were 

 initiated by the male. A new behavior was noted 19 days before final 

 entry into the nest when the male began to present food to the female. 

 This was done anywhere, not necessarily near the nest tree. Finally, 

 bark presentation was frequent among crowned hornbills. Ranger 

 found that the female would take bark with ready interest from her 

 mate, then bite it to pieces. 



(f) Intruders. I have described intrusions on nesting casf|ued 

 hornbills by members of their own species. Apparently a similar 

 phenomenon takes place among crowned hornbills. Speaking of a 

 feeding visit Ranger wrote "the male and a young intruder arrived, 

 and this drew a single sharp cry from the female. . . . The male then 

 delivered an item and resumed his chasing of the intruder." This male 

 subsequently delivered "13 items of food and bark, but all the time 

 was worried by the young trespasser who followed him again and 

 again to the nest. ..." I was unable to tell whether the female in- 

 truders I saw by Bycanistes nests were young birds or not. The male 

 intruders were all adults. Ranger has also written of the nesting 

 female rattling her bill in the entrance. He describes this "habit 

 rattling" as useless activity. This was not true of casqued hornbills. 

 Every time I saw a female rattling her bill there was some cause, 

 such as presence of intruders, to evoke this alarm signal. 



(g) Plastering. Photographs of nest entrances presented by 

 Ranger show that the cement walls look much the same as those con- 

 structed by Bycanistes. The female crowned hornbill has the same 

 technique of plastering. "Always the bill works rapidly in vibratory 



