NO. 9 CASQUED HORNBILLS — KILHAM 37 



another crowned hornbill (Tockus alboterminattts) which occurs in 

 South Africa. Comparisons will be made first in regard to differences 

 of behavior, then to points of similarity with Bycanistes. All observa- 

 tions and quotations on the crowned hornbill are from Ranger's 

 publications. 



Differences in behavior between Bycanistes and Tockus. — (a) 

 Crowned hornbills have a definite territory which is fairly extensive, 

 is defended against trespassing hornbills, and is maintained year after 

 year by the same pair which temporarily share it wdth the offspring 

 of each season. I found little evidence that Bycanistes subcylindricus 

 maintains a definite territory other than the immediate vicinity of the 

 nest tree. 



(b) Crowned hornbills live more extensively on insects. This 

 greater consumption of animal protein is reflected in their white 

 excreta. In feeding his mate at the nest, the male carries the food, 

 usually a single insect, at his bill tip. He does not load his gullet, then 

 cough up fruits one at a time as do male casqued hornbills. Further- 

 more, crowned hornbills make casts of indigestible seeds, pips, and 

 hard parts of insects. Casqued hornbills, on the other hand, pass every- 

 thing out in the feces — even large fruit stones, whole baby mice, and 

 mantis nests. 



(c) There are a number of differences in the manner of plastering 

 nest walls. Crowned hornbills make plaster of feces, finer soil from 

 the floor of the nest, and insect remains. According to Ranger "the 

 female does not swallow anything for the purpose of disgorging it 

 in the form of plaster," and "the male plays no part whatever in 

 plastering the nest hole." Bycanistes collect soil and lumps of earth 

 from the ground. Both sexes do this, but the male brings the most 

 and is a kind of "bricklayer's helper," supplying his mate who does 

 the actual plastering. 



(d) A distinction between Bycanistes and Tockus lies in the time 

 of emergence of the female from the nest. Ranger (1955, personal 

 communication) has extensive data on this subject. He has found that 

 the female may emerge 62 to 74 days after being walled in. At this 

 time the precocious young reseal the entrance. Both parents then 

 feed the young which emerge 19 to 34 days later. Moreau (1936) 

 has collected similar information in regard to Tockus deckeni and 

 T. alboterminatus. 



Similarities in behavior between Bycanistes and Tockus. — A close 

 relationship between the two genera of hornbills is indicated by simi- 

 larities in their behavior patterns. Many of Ranger's descriptions 

 (1949-52) of the habits of Tockus alboterminatus australis apply 



