36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



tail coverts in both were well developed. In both nestlings the bill showed no trace 

 of a casque and was a yellowish-horn color ; the feet were dark lead color ; the 

 skin light pinkish ; the iris bluish gray. The tail folded up against the back so 

 well as to look like a definite adaptation to living in crowded quarters. In fact 

 it seemed to be muscularly easier for the birds to hold their tails up than to 

 straighten them out [pi. 6, fig. 2]. One of the nestlings when put on the ground 

 fell over forward on its head and breast and the tail remained sticking straight 

 up in the air as though the bird were unable to drop it into what would be con- 

 sidered the normal position. The adult female when about to enter a nest before 

 egg-laying usually begins to molt and is for some time thereafter in quite a help- 

 less condition. New feathers grow in while the eggs are incubating and the 

 young growing to the flying stage. The female taken from the nest had all the 

 new tail feathers well developed but all of them were still basally enclosed in 

 their sheaths. The bird was still missing the outermost secondaries and innermost 

 primaries but the other remiges were there, most of them more or less still in 

 their sheaths basally. The bird could fly only very poorly and seemed dazzled by 

 the light. Several times I let it go and each time it flew or rather half fluttered, 

 half flopped through the air very laboriously for a short distance and stopped by 

 smashing against a tree or the side of my tent. 



I had some evidence that pied hornbills also breed in March. From 

 November on I had been observing a pair of casqued hornbills in the 

 Botanical Gardens and had kept watch on a squirrel hole 50 feet up 

 in a nearby tree. It was not until March i that I noticed a pair of 

 pied hornbills showing any interest. At 7 ."30 a.m. a pair were preen- 

 ing nearby. Between them they made 10 visits to the hole, poking 

 their bills inside. When a crowned hornbill appeared, they chased it 

 away. The following day the pair were at the hole morning and eve- 

 ning. On March 8 I saw them putting their bills into the hole and 

 tossing out debris. I had no subsequent evidence that the pair nested. 

 The hole may have been occupied by a squirrel which I had seen using 

 it previously. Apparently smaller hornbills may compete with hole- 

 nesting mammals. On February 18 I was driving near Kaboona, in the 

 arid country of Karamoja, when I noticed a pair of Jackson's horn- 

 bills (Tockiis jacksoni) catching insects and flying to a 2-inch hole 

 in a dead tree. When I returned 4 days later the pair were still in- 

 specting the nest hole. Thinking young hornbills might be in the tree, 

 I cut it down. To my surprise, the cavity contained a mother bush 

 baby (Galago scnegalensis) with a mouse-sized young one. These 

 limited observations may have interest because I could find no breeding 

 dates for these three species of Tockus in eastern Uganda. 



The investigations of Gordon Ranger (1949-52) offer an opportunity 

 to compare the habits of Bycanistes with those of Tockus in some 

 detail. These investigations on African hornbills are the most com- 

 plete known to me. They have extended over many years and concern 



