60 Double offspring in the southern ground hornbill reared at <strong>Ostrava</strong> <strong>Zoo</strong> Ivo Firla Southern ground hornbills (Bucorvus leadbeateri) have been successfully bred since 2007 at <strong>Ostrava</strong> <strong>Zoo</strong>. Following the failure to hand-rear the juvenile hatched in 2006, the bird hatched a year later was successfully reared by parents. Seeing that the female laid each time two fertile eggs, the team was considering possible use of the other egg, as they wanted to avoid any artificial rearing. Options included placing one egg under a different female in a different zoo provided one was available with unfertilised eggs or attempting at natural rearing of both chicks. In early December 2008, the birds started visiting their nest-box as with the previous years, first the female with the male following. Some 14 days later, on 16 December, the female laid the first egg and then another four days after, on 20 December. <strong>The</strong> eggs were removed one by one, put into the incubator and replaced with artificial eggs, but as they turned out to be unfertilised, the artificial eggs were removed and everyone believed the female would lay another clutch. This did happen and the female laid her third egg on 18 January, with another following four days after (on 22 January) as with the previous clutch. Again, these eggs were put into the incubator one by one and replaced with artificial eggs. Following a week of incubation, the eggs were checked using a candle lamp and both found to have been impregnated. <strong>The</strong>n they were undergoing successful development. On 25 February, when the chick was ready to hatch and started to call, the egg was placed under the female and one artificial egg removed at the same time. A day later, the egg was pre-hatched, with the chick intensely calling. On 27 February, the chick hatched, weighing 64 grams. Three days after, on 2 March, the chick from the fourth egg still left inside the incubator hatched as well. As no suitable female under which the second chick could be placed was available in other zoos at the moment, the team opted for the second alternative of attempting at rearing both chicks by a single female, based upon experience transferred from the colleagues at Prague <strong>Zoo</strong>. Placing both chicks immediately upon hatching is not possible, with the different size of the chicks being the issue, where the older bird will eat the food offered by the mother, leaving the younger chick starving. Thus, the younger birds need to be trained by hand-feeding to make sure they will able to take food properly. Once this was done, the chicks were exchanged on 4 March - five days after the first chick was hatched - where the chick brooded by the female was replaced by the other chick and moved into the incubator, where it was fed by hand another five days. Subsequently, there was another exchange and all was repeated. It resulted from routine checks and weighing that the parents were taking good care of each young bird and in fact did not matter the chick exchanges at all. As of 16 March, when the chicks were 15 and 18 days old, they were both left under the mother. As there was no option of visual check if the younger and lesser chick would take enough food or not, both birds were weighed on a periodical basis, which made the team assured the parents' care of both young hornbills was excellent. <strong>The</strong> older chick attacked its younger sibling from time to time, namely in feeding. <strong>The</strong> inspection by weighing was carried out until about middle of May. Somewhere between day 82 and 84, the young birds left the nest-box for the first time. Although already able to take food by themselves, the birds still begged from time to time, keeping themselves being fed by their parents. After blood was sampled for DNA testing, both juveniles were found to be females. Any critical periods occur namely in the
eginnings when the young are fed by the mother and the stronger of the two is distinctively more active than the younger one. <strong>The</strong> female turned out to be an excellent mother, devoting her attention to both young hornbills. 61
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