28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



ladders and an African was preparing to climb up and open the nest. 

 As we stood below, a foreign female flew in and lighted on the edge 

 of the nest. I thought that the mother had already emerged, but it 

 was later discovered that the mother and young were inside. 



Territory. — Neighboring pairs of hornbills tolerated each other 

 well. For example, nests 7 and 10 in Mpanga Forest were within 

 120 feet of each other and a third pair made persistent attempts to 

 nest within an equal distance. Within this triangle I could watch 

 activities of all three pairs at one time. They paid no attention to each 

 other, their sense of territory apparently being limited to the nest tree 

 and its immediate vicinity. Some trespassing was accidental and with- 

 out interest in the nest itself. Thus nest 4 was centrally located in 

 Mpanga Forest so hornbills engaged in their various activities fre- 

 quently came near it. The male from this nest did more chasing than 

 any other I had under observation. He had a peculiar habit of perch- 

 ing during the day within 10 feet of his nest hole. No other male 

 perched close to its nest. Some might occasionally perch within 100 

 feet, but usually I saw males near their nest trees only on feeding 

 visits. Females were frequently alone for 45 minutes to an hour at 

 a time, and during these periods the nest tree was open to intruders. 

 Hornbills may have a sense of territory in relation to roosting areas ; 

 I did not make sufficient observations to determine whether this 

 was so. 



Aggregations of hornbills. — Sometimes a number of hornbills would 

 come together, usually owing to a common attraction such as a flight 

 of insects, a fruiting tree, or a passing hawk. This did not appear to 

 be true flocking. Nine was the largest number of hornbills I ever saw 

 together. They were in our garden on August 26. Other observers 

 told me that they had seen larger gatherings. On November 28 I 

 watched two males and four females closely besetting a harrier hawk. 

 A week later I came across what appeared to be the same group in 

 the same area of Mpanga Forest. This time a band of redtail monkeys 

 were working along the forest edge. Six female and two male horn- 

 bills followed along with them sitting in the same trees but making 

 no noise. I believe that the association was an idle one, for the horn- 

 bills were playing with sticks and showed no alarm. The excess of 

 females was of interest. Pairs of hornbills were also frequent during 

 the nesting season. I wondered if there had not been enough nesting 

 sites to go around. On February 15 I saw a curious association of 

 two adult male hornbills. They came to our garden and hunted to- 

 gether closely, going over cracks and crevices in a big tree. Two 



