NO. 9 CASQUED HORNBILLS — KILHAM 9 



ing a hole in a stump 25 feet above ground. I suspected that they were 

 trying to find an alternative to their other nest cavity. They both 

 lit on the rim together, but he kept bending in to remove bits of rotten 

 wood up to 2 inches long. She took a few of these from his bill, but 

 let him continue the excavating. In January I observed further pio- 

 neering by a male under unusual circumstances. The male of nest 5 

 had been killed and his mate had broken out by January 2. I arrived 

 shortly after 9 a.m. To my surprise, I saw a male picking up dirt in 

 the forest clearing. I had seen no signs of nest construction for many 

 weeks. The male's flight led me to the abandoned nest. Here he 

 perched by his mate, then clung to the lower rim of the hole and spent 

 some minutes poking his bill about inside. His mate scrutinized the 

 hole carefully before flying to it. She clung to the rim momentarily, 

 but dropped away as if frightened. This desultory type of inspection 

 went on for 3 weeks. After losing interest in the hole, presumably 

 due to lateness of the season, the pair continued to use the tree as a 

 perch. 



Location of nests. — Locations of nests are summarized in table i. 

 It was apparent that casqued hornbills preferred the largest trees and 

 a hole as far from the ground as possible. Very large trees were 

 scarce, even in Mpanga Forest. Nest 3 was in one of the finest trees 

 {Antiaris toxicaria) in the forest, a huge specimen 6 feet in diameter 

 at breast height and possibly 150 feet tall. The large branches sup- 

 ported a growth of epiphytic plants and were draped with lianas. Text 

 figure I is a sketch of the nest opening in a limb 85 feet above the 

 ground and shows the male as he always perched preparatory to bend- 

 ing over to feed his mate. Such large trees, free of limbs for 60 or 

 70 feet, were impossible to climb. Nests were often located where a 

 large limb had broken off, exposing an area of decay. Such a site is 

 illustrated by text figure 2. Plate 3, figure i, is a photograph of a large 

 tree in the open, showing location of a nest entrance in the stub of a 

 broken branch. Nest 5 was located in a huge arching limb of a 

 Piptadenia, as shown in plate 3, figure 2. Some few nests were in less 

 favorable sites. Nest 16, for example, was only 30 feet from the 

 ground in a comparatively small tree. It was relatively easy for an 

 African to climb up and open it. Three nest trees were isolated and 

 in the open and the remainder were in forests. Nest 2 was in a unique 

 position. The cavity was located in a crotch in the top of an exceed- 

 ingly tall, dead stump. Since the entrance faced vertically upward, 

 one wondered what might happen in a heavy rain storm. 



Gatheriny dirt for bidlding at nest i. — I learned the most about wall 

 building from a pair of hornbills in Mpanga Forest. Their hole was 



