Abstract
The Bird department of the Houston ~ Zoological Gardens received a ·~ newly imported pair of Crowned ll>-
Hornbills Tockus alhoterminatus in ~
October 1989. This arboreal species is ~ a resident of southcentral and southeast -§ African riparian, montane, and coastal ct forests. The birds are rather plain in appearance compared to some of the other Tockus hornbill species, however, they have their own appeal. The upperparts, head and neck are a dusky brown, with the feathers of the back of the head and neck shaggy and white-tipped; it is the appearance
of this feathering which presumably gives them their common name. The breast is grayish, beneath this the rest
of the underparts are snow white and Weighing a chick 27 days of age. Average weight, 200 g.
the tail is tipped in white (Fry, Keith, Urban, 1988).
The birds can be sexed visually, primarily by their eye color. The iris of the males are red and the females a light yellow. Additionally, the male is a bit larger in overall size. The hills of both sexes are a translucent orange-red, with a narrow creamy yellow band at the hase, with the male having a larger ridge or small casque atop his hill (Maclean, 1993).
After a thirty-day quarantine at the zoo the birds were housed in their own 12 ft. long, x 10 ft. wide x 7 ft. high exhibit in a row of outdoor aviaries where they remained for 17 months. Throughout this period they excavated wood shavings from a horizontal plywood nestbox and even hegan plastering food items and feces, with their hills, around its opening. The staff was very encouraged by this behavior as this is the beginning of the typical hornhill mode of reproduction. This type of behavior leads to the female heing immured in the nest cavity with an opening reduced to only a narrow slit, through which the male feeds her during the entire nesting period. However, while at this location the hirds never progressed past this initial stage.
In April 1991, the pair was moved to a mixed species exhihit measuring 20 ft. long x 20 ft. wide x 12 ft. high in a new series of outdoor aviaries, The Fischer Bird Gardens. They were joined hy a pair of White Headed Buffalo Weavers Dinamellia dinamella and a pair of Hottentot Teal Anas punctata as cagemates. The hornhills have always heen fed small halls of Nebraska Brand Bird of Prey Diet, soaked dog, cat and primate chows and a chopped fruit mix (papaya, cooked sweet potato, apple, grapes, soaked raisins) and chopped greens. An assortment of live food was offered daily: mealworrns, waxworms, crickets. furred and pinkie mice. The hirds are also adept at catching a variety of wild insect prey on their own. In addition, the hornhills have heen observed eating sunflower seeds and perhaps other seeds from the Buffalo Weaver's diet.
When we transferred the hornbills we moved their original nesthox (24 in. long x 12 in. wide x 13 in. deep into their new quarters. Shortly thereafter, two other nestboxes were added in the exhibit in case the first one was not to their liking. One was a vertical 37 in. long x 14 in. wide x 13 in. tall plywood hox with a natural tree knothole having a six inch diameter opening attached near the top of the hox as the nest entrance. The other was a 13 in. diameter hollow palm log, again placed vertically with the entrance near the top.
Over the course of the next two years our pair exhihited a variety of courtship and breeding behaviors. The male feeding the female, the male chasing the female, the male trying to lure the female to the nesthox with food and high-pitched calls, each hird entering the nestboxes and pulling woodshavings out, and again plastering around the nest openings. These are all typical hornhill hehaviors. However, the birds never seemed to get "over the hump," their activity would increase for a while and then activity would taper off. The hird staff finally decided we had been patient long enough and hegan consulting a numher of zoo professionals for advice.
These discussions resulted in two suggestions for the hreeding of Tockus species in captivity. First, the nestbox entrance should he very small. The opening should just be wide enough for the hirds to fit their hills through. Secondly, the nest entrance should he located toward the bottom of the hox rather than the top of the hox so that the female can reach the entrance from a hrooding position. With these in mind, a 13 in. on long x 13 in. wide x 19 in. tall nestbox was constructed of half inch plywood. A teardrop shaped opening, four inches tall and two inches wide, was made on the lower third of the nesthox face. The hox wa equipped with a shelf in the upper third which allowed the female to jump to if frightened.