Hwange - Ground Hornbill Stronghold?

Is Hwange one of the remaining Ground Hornbill strongholds?

The Ground Hornbill conservation project (www.mabulagroundhornbillconservationproject.org.za) states that their work shows that the Ground Hornbill qualifies for "Endangered" status and possibly "Critically Endangered" status under the IUCN guidelines and that makes me wonder if Hwange is one of the last remaining strongholds. I have lived and worked full-time in Hwange for over 5 years now and we seem to be seeing more and more Bucorvus leadbeateri.
Once I counted 21 individual birds in the course of a days lion work in Hwange (probably less than 100km of driving!)

The photo above is one adult that flew into the tree ahead of my truck and then let me park underneath and photograph it.

The Hwange Birder