<em>By
Rebecca Bates, Primary Keeper
Tracy Aviary, Salt Lake City, UT</em>

<strong>Summary </strong>
During the 2009 breeding season, the southern ground hornbills (Bucorvus leadbeateri) at the Tracy Aviary were housed as a family group consisting of the dominant breeding pair and two juvenile females. Since the breeding pair had successfully raised nine chicks with varying levels of assistance, and they were not a high priority to breed, we decided to allow them to try to breed completely without assistance. We provided daily dietary enrichment of mice, chicks, rabbits, nuts, fruits, vegetables, and bugs in a manner that encouraged foraging behavior. Soon the male was displaying with food and leaves to the female and they were frequently heard calling back and forth to each other.

Sadly the female abandoned the first clutch half way through incubation. The eggs were candled and no signs of fertility were seen. The second clutch was developing normally when the eggs were candled half way through incubation, but one egg had a small hole. Since hornbills only raise one chick even if both eggs hatch, this egg was pulled and artificially incubated. The second chick hatched without assistance. The feedings were increased to three times per day to give the hornbills access to fresh food to feed the chick at all times. The male diligently provided the female with food as soon as the food pan was placed in the exhibit. Surprisingly, after a few days the juveniles began presenting the female with food. The male allowed this but watched very closely. Perhaps even more surprisingly, the male began to feed the female less and allow the juveniles to provide the majority of the food to the female.

As the chick grew, the female would start spending more and more time off the nest. On several occasions, the oldest juvenile was seen brooding the chick while the female was off the nest. The juveniles continued to care for the chick even after it had fledged. According to their natural history, hornbills stay with their family group for five to six years and assist in chick rearing and territorial defense. Based on my observations and their natural history, I believe much of their breeding behavior is learned. Experience watching and participating in breeding like our juveniles did, will likely make them more successful breeders. I believe that if zoos are to have a sustainable breeding population of southern ground hornbills more effort should be made to keep the juveniles with their parents for as long as possible and allow them to observe and participate on future breeding attempts.

<img class="alignnone size-full wp-image-1845" title="ground_hornbills" src="http://aecetia.net/gws/aazk/wp-content/uploads/ground_hornbills.jpg" alt="ground_hornbills" width="635" height="509" />

<strong>Ground hornbill juveniles playing in their exhibit at the Tracy Aviary. </strong><strong><em>(Photo: Allyce Linder)</em></strong>

<strong>Introduction</strong>
Southern ground hornbills are the second largest hornbill and can be found in the savannahs and woodlands of Kenya, Burundi, Nambia, Botswana and South Africa. They are found in family groups of two to 11 birds comprised of a dominant breeding pair and several juvenile and non-dominant male helpers. These groups hunt together feeding mainly on arthropods, but they have also been seen taking larger prey such as snakes, hares and tortoises. The group is sedentary and becomes very territorial during breeding season going so far as to swoop on and killed a Verreaux’s eagle (Aquila verreauxii) when it ventured too close to the nest cavity (del Hoyo, 2001).

Ground hornbills are unique among hornbills because they nest in open cavities in trees or on rock cliffs instead of sealing themselves into a tree cavity. Only the dominant pair will breed. The dominate female will lay two eggs three to five days apart. The eggs are incubated for 37-43 days.  If both eggs hatch, the younger sibling will almost always die of parental neglect. During incubation and chick rearing, the dominant female is provided with food by all members of the group. The chick will fledge after 86 days but will stay with the family group for five to six years until it reaches sexual maturity and males may stay much longer (del Hoyo, 2001).

Although the species has been classified as a species of least concern on the 2009 IUCN red list, many conservationists are concerned about the stability of the population due to the political instability of the countries within their range. They fear that a civil war could not only kill many individuals, but also destroy their habitat making it very difficult for their population to recover. The only country in which they occur that is politically stable is South Africa, and the South African population is declining. They have lost 50% of their original habitat to human encroachment and are often the victims of close association with humans through loss of large dead trees used as nest sites, incidental trapping, shooting and poisoning. For this reason, the Mabula Ground Hornbill Conservation Project has been working to establish hornbill troops in the Mabula reserve in South Africa which was historically within their range. This effort entails pulling the second chick from wild nests and hand- rearing it.

The first attempt to introduce a group of hand-reared chicks was met with many obstacles. The youngsters were so naïve that they had to be provided with supplemental food and a shepherd was hired to follow the troop around. He made sure they didn’t get eaten by predators and found a proper roost for the night. This care continued until the project received an adult male from rehab whose troop had been poisoned. The male was introduced to the juveniles and he accepted them and took over care. With the adult male helping the youngsters find food and look out for predators, the troop was soon self-sufficient. Happily, the Mabula Ground Hornbill Conservation Project reported their first successful fledging from a reintroduced group. The parents were a hand-reared female and a rehabilitated male.  This illustrates the importance of parental care for this species (Turner, 2007).

At the Tracy Aviary, we believe that the group interactions are important for proper development of the chicks, so our southern ground hornbills are………..

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