44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



forest trees. My unusual opportunity to study their breeding and 

 other habits in the vicinity of Entebbe has been most fortunate. 



SUMMARY 



Sixteen nesting pairs of casqued hornbills (Bycanistes sitbcylin- 

 dricus) have been studied in the vicinity of Entebbe, Uganda. An 

 unusual concentration of nests was found in the Mpanga Research 

 Forest. 



In courtship the male presented his mate w^ith food and bits of 

 bark or sticks. Mutual preening and calls back and forth were im- 

 portant in maintenance of the pair bond. 



The male did the pioneering in exploration of possible nest sites 

 and tried to entice the female to them with wailing cries. Plastering 

 was done by the female from the inside of the nest cavity, using a 

 rapid tapping with the side of her bill tip. Both sexes flew to the 

 ground to collect dirt for building. Most of this, however, was done 

 by the male. He attended the female, furnishing her with pellets for 

 construction of the nest wall. Termite earth was preferred for 

 building. 



Two eggs are laid. Although both may hatch, only one chick is 

 raised. 



Male hornbills feed their mates about every 30 to 60 minutes, 

 heaving up fruits held in their gullets. Often a stick or piece of bark 

 is presented first. 



Nest sanitation is accomplished by female and chick expelling feces 

 through the entrance. The female may also toss debris out with her 

 bill. If such debris collects outside of the entrance, it is regularly 

 cleared away by the male. 



Ants which swarm in some hombill nests may act as scavengers 

 and keep down insect fauna. 



Females walled within nests can be extremely noisy if alarmed. 



Observations made at one-third and two-thirds through the nesting 

 period indicate that females have a gradual molt. Two females re- 

 moved when two-thirds through their nesting could fly readily. 



The total period a female was walled in one nest was 119 ±2 days. 

 A young hornbill, captured two days after emerging, was in full 

 plumage. 



The majority of casqued hornbills in eastern Uganda probably begin 

 nesting in September and break out in January. 



A hornbill territory is confined largely to the vicinit}' of the nest 

 tree. 



