42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



when she swallowed it." I have previously described an almost identi- 

 cal situation which took place in Mpanga Forest. 



Important differences in appearance of hornbills are located about 

 the head, the region which can be seen best through a nest opening. 

 Head feathers in birds of all ages express emotions. In young birds 

 the feathers at the base of the upper mandible are brown instead of 

 black. The huge, forward-projecting casque of the male is his chief 

 sexual characteristic and white skin around the eye is a peculiarity of 

 the female. Many African hornbills have brightly colored patches 

 of skin and wattles about the head and neck. These, however, are en- 

 tirely lacking in Bycanistes suhcylindricus. One would like to know 

 what part these bright colors may play in courtship performances. 



Coition in one pair of casqued hornbills took place without any 

 special courtship other than some touching of bills. The pair were 

 returning to their nest, after gathering termite earth. Moreau (1936) 

 found that copulation took place in Bycanistes hrevis just after the 

 female had emerged from her morning's work and about 10 days 

 before the nest wall was complete. 



Good nesting sites are probably used annually. Pitman (personal 

 communication, 1955) believed that the nest hole that I watched in 

 the Botanical Gardens had been used in 1947 and in 1949. At nest i 

 the pair tried for weeks to close the opening. Interest, however, began 

 to fall oft' a week after coition, a situation that paralleled one de- 

 scribed by Moreau (1936) in Usambara. Pairs of Bycanistes hrevis 

 tried for 2 years to nest at one site without success. "In both years," 

 Moreau wrote, "building continued after copulation had taken place, 

 and when work had ceased, both birds still showed a keen interest in 

 the nest hole." Failure at the nest in Mpanga Forest may have been 

 due to the large size of the opening. Other factors could have been 

 operative also. The pair, or perhaps only the female, for example, 

 may have been young and inexperienced. It is difficult to follow 

 Moreau's hypothesis that in Usambara, failure to complete nests was 

 due to the male's running out of saliva. 



Casqued hornbills probably lay two eggs to insure that a single 

 healthy chick is produced. The young bird becomes so large that the 

 nest might be overcrowded if two chicks survived. Crowned hornbills 

 have two to three young. The mother, however, leaves the nest some 

 weeks ahead of time. This not only makes more room for the young 

 but enables her to help in the feeding. 



The length of time a female is walled in a nest (119 days for nest 

 5) does not appear unusual for a bird of hornbill size to lay eggs, 

 incubate, and rear a young one. One can use Wahlberg's eagle 



