NO. 9 CASQUED HORNBILLS — KILHAM 43 



(Aqtiila zvahlbergi) for comparison. It is approximately the size of a 

 casqued hornbill and has been studied by Leslie H. Brown (1952) in 

 Kenya Colony. He observed an incubation period of 46 days and a 

 fledgling period of 72 days at a nest where a single eaglet was raised. 

 This gave a total of 118 days. The total time is about the same as for 

 the casqued hornbill, which, I have estimated, leaves the nest when 

 10 to II weeks of age. I would have supposed that young hornbills 

 would grow more slowly on a fruit diet — they had animal food only 

 occasionally. However, as indicated by white matter in the feces, 

 they may have had more animal protein, particularly in the form of 

 smaller insects, than I realized. It was almost impossible to feed my 

 young captive hornbills on fruit alone. The volume required was 

 exhausting. We reduced the number of feedings, first by coating 

 pieces of pawpaw with powdered milk, then by giving each bird six to 

 eight half -grown mice a day. 



Intrusions of foreign hornbills on nesting pairs of their own species 

 presented an interesting stud3^ In a few instances the intruders came 

 in pairs. There were many free pairs of hornbills throughout the 

 nesting season and I wondered if these were not an index of an in- 

 creasing shortage of suitable nest trees. Intrusions by single female 

 hornbills were more difficult to explain. At one nest the same female 

 apparently stayed around for months, and possibly attacked and 

 crippled the young one soon after it left the nest. Several explana- 

 tions suggest themselves. First, intruding females may have been 

 offspring of the season before, unwilling to leave their parents or, 

 second, they may have been unmated adults attracted by a seemingly 

 lone male; possibly they fell into both categories. Some of them 

 seemed to be more attracted to the nest itself and others to the male, 

 coming and going with him as he made his feeding visits. I had an 

 impression that there was an excess of females in the hornbill 

 population. 



In conclusion, the pleasure of watching hornbills comes from their 

 love of play, unexpected agility, clownishness, and seeming intelli- 

 gence. This last quality is difficult to assess. The intelligence of the 

 crow family is well recognized. I have kept tame blue jays, crows, 

 and magpies and rate my captive hornbills on the same level. Both 

 groups are playful and curious, examining new objects with interest. 

 They have a wide range of vocal expression. The large eyes of horn- 

 bills, together with expressive movements of head feathers, give an 

 impression of intelligence which is hard to disregard. Whatever their 

 mental capacity, however, it is difficult to see how these birds can 

 adapt themselves to civilization, as they are destined to inhabit large 



