Abstract
Introduction
The Southern Ground Hornbill
(SGH) and its northern congenor, the
Abyssinian Ground Hornbill B. abyssinicus
(AGH), are the largest and
most carnivoro us h o rn b ills in the
world. These birds inhabit wooded
savanna and steppe, spending most
of the day walking around in search
of small prey animals but taking to
trees and rocky outcrops to rest and
nest.
The SGH is widely distributed in
the moist savanna of Africa south of
the equator with a total range of
about 4.5 million sq. km of which
less than 2% extends into South
Africa. Outside the limits of South
Africa it is not recorded as having
declined in its range, but within the
country over the last fifty years has
disappeared from about 70% of its
original distribution (Cyrus & Robson
1980, Vernon 1986, Tarboton et al.
1987). Only land that is provided for
game reserves, forestry or tribal lands
support populations of the birds.
They occur in small groups varying
from 2 to 11 individuals. In the
Kruger National Park (KNP), 98% of
the SGH population are groups of
this size, 72% are groups of three to
five and 2% is solitary (Kemp 1990).
Groups occupy territory of about
100 sq. km per group. A number of
reasons have been suggested as contributing
to this decline including
dense human settlement, felling of
trees in savanna, forestation of grasslands,
direct persecution and indirect
poisoning.
Breeding Program
With the current status of the SGH
in South Africa in mind, an attempt
was made to establish a breeding
program at the National Zoological
Gardens (NZG). On the suggestion of
Dr. Alan Kemp of the Transvaal
Museum, it was decided to harvest
second hatched chicks, which die of
starvation in nature. This was agreed
to by the National Parks Board and,
since the mid-1980s, a handful of
chicks have been harvested in the
KNP. Unfortunately only a few have
been successfully reared. Fortunately
a few adult birds have been acquired
and currently the NZG has two males
and two females, with the strong
possibility of an additional three
birds from Zimbabwe. Two other
institutions, namely Umgeni River
Bird Park (URBP) and World of Birds
at Hout Bay, are also currently very
interested in being part of the joint
effort in breeding the SGH. The URBP
currently has an adult female.
During 1990 a breeding unit was
constructed at the NZG covering an
area of about 400m of natural bush in
a quiet corner of the zoo. The birds
have settled down extremely well
and during July 1991 started to excavate
a nesting area in a stoney ridge.
In the KNP, adult turnover has
been estimated at 1.5% per annum,
groups fledge on average one chick
every 9.3 years which attain maturity
at about six years of age (Kemp
1990). With this slow reproductive
rate, it is of great importance to
establish as many breeding groups as
possible, thus maximizing production.
Both species of ground hornbill
have been bred repeatedly in captivity
(e.g. Olney 1985). Observations
on captive breeding of the AGH suggest
that captive propagation can far
exceed that in the wild, by rearing
both hatchlings and by removing
fledglings to produce rapid and
repeated relaying (Penny 1975).