Friday, January 6, 2012

Bigblackblushingchickens and the art of using a Ladder

Adult Male Southern Ground Hornbill - sometimes we
are the ones that get scrutinised!
As part of its activities, our Lowveld-Kruger National Large Bird project has focused on locating and monitoring as many groups and nesting sites of the Southern Ground Hornbill Bucorvus leadbeateri in the Kruger National Park since its inception in 2007. Part of the activities also include the harvesting of a set quota of second chicks from selected nests to augment the captive breeding population that is used by the South African Southern Ground Hornbill Action Group (SASGHAG) to attempt to re-establish this species in its historical range in the country. The Southern Ground Hornbill is currently listed as Endangered according to the IUCN’s Red List and is now largely restricted to protected areas in South Africa with a few small groups still being found on private land in the Eastern Cape, KwaZulu-Natal and along the escarpment. Due to their generally shy nature (except for those few birds that have been seduced by the tidbits offered by unthinking tourists) and large patch of red skin on the face, I prefer to call them Bigblackblushingchickens.

Two eggs is the norm for this species
Southern Ground Hornbills mostly lay two eggs of which only one chick eventually survives to the fledging stage. The weaker chick does not survive the competition for food, etc in a Cain-and-Able-like situation similar to some large eagles, and it is therefore possible to harvest this chick for captive rearing to play an important role in terms of the overall conservation of the species in the country as part of the captive breeding population. The hand-rearing and captive breeding process is managed by our partners in the SASGHAG such as the Mabula Ground Hornbill Project, Mpumalanga Parks (Delecia Gunn), Johannesburg Zoo and the NZG, Pretoria. However, before we even get to the stage where chicks can be harvested, there is a lot of work that must be done.
We encourage rangers, guides and tourists in the Kruger National Park to report any sightings of groups of birds or nesting activities to us and have so far identified over 150 individual groups of birds across the 2 million hectares of the Park. These range in size from two to as many as nine birds. In the Kruger National Park, these birds mostly nest in suitable cavities in large trees, often along drainage lines. A range of tree species are used. There are also two known sites where potholes in a cliff were used to nest in, but neither of these are currently active.
Female giving us a beady eye
while huddling over over her eggs
Finding the nests of these birds is not as easy as it sounds as they tend to be quite secretive about its location and the birds themselves can, despite their large size, disappear quite quickly in the bush, especially during the wet season. We therefore often go out very early in the morning to try and find the birds when they start calling at first light. This means that one gets up at about 02.30 in the morning to be at a site by 3.30-4am. Once the birds have been located, one hopes to either see the female move off in a particular direction to a nest after calling, or to quietly try and follow the group that will eventually make their way to the nest to provide food to the incubating female or, if the breeding attempt has advanced that far, to the fast-growing nestling. This is often the time of year when Ground Hornbills are most visible and when all members of the group can be seen carrying an array of food items to the nest.
Once the nest has been located, it is monitored throughout the season and, if it is used for more than a season, for as long as possible. One known nesting site on the Letaba river has been in use for almost 40 years! This requires a lot of time and effort and we travel lots of kilometres annually during the breeding season to check on nests and how the breeding season progresses at each site. In fact, the demands are such that we can realistically only focus on about 30-40 nests annually (See Google Earth image).
Nest sites currently monitored in KNP
The monitoring season starts in October when all known nests are visited and checked for activity. The commencement of breeding is often determined by the first decent rains. This is followed by another visit a few weeks later to check for eggs and, if those are present, to “candle” them to obtain an idea of when they are likely to hatch. Candling involves looking at the egg contents by shining a flashlight through them in a poorly-lit environment. This is quite a specialised process and we make use of the services of Mike Harman (Jhb Zoo) and Eugene Marais (NZG) to assist us in this regard. The poorly-lit area is created by covering the two observers with a thick, dark cloth and you can imagine the numerous curious stares we have encountered from passers-by over the years. One can only wonder what they made of two middle-aged men hunkering under a dark sheet in the bush during broad daylight!
Putting heads together? No, just candling an egg
A rather steep climb in this case
and the ladder just makes it
The nests are located in large trees of a range of species of all shapes and the height of the nest entrance and depth of cavity vary considerably between groups. Some cavities are fairly easy to access while other provide a particular challenge. This is often where the art of using a ladder comes in. Knowing the exact location and configuration of each nest does help, but it’s not as simple that. Placing the ladder against the tree at the suitable height, ensuring that it is stable before climbing up and other aspects are all standard considerations when using a ladder in the bush. The ladders often need to be carried for some distance to the nest tree and it always helps to have a volunteer or two to accompany you to assist with this.
Female leaving the nest
Cavities in trees in the African bush are however not just sought after by Ground Hornbills as nesting sites, but are also used by a range of other creatures ranging from diminutive rodents and bush-babies to slightly more tricky customers such as genets, the odd snake ranging from pythons to mambas and a number of other birds such as Barn Owls. So far, we have been fortunate to not encounter anything larger such as leopard. The ability to duck and dive and rapidly descend from a ladder should one of the more aggressive creatures be encountered is often another aspect of ladder use that is often underestimated, especially if it is leaning precariously against the slippery branches of a tree and you are about 12 metres above ground. It is however a skill that is rather quickly acquired should such a situation arise!
Genet hiding in an old SGH nest
Once the candling has been done, we keep an eye on specific nests that have been identified for harvesting to ensure that this can happen at the most opportune time. Harvesting generally takes place through December, but is mostly concentrated in the latter half of this month which can play havoc with any festive season plans and arrangements for those concerned! Both harvested and un-harvested nests are monitored thereafter until the nestlings are old enough to ring at about 60 days of age. This takes place from late January to mid-March, depending on when the chicks hatched.
Barn Owls flying out of an old SGH nest
We have to date fitted 17 chicks with colour-rings in the Kruger National Park and have been quite successful in obtaining reports of re-sightings of these birds from visitors to the Park. This number is set to increase considerably in the next three months when this season’s chicks will be ringed. Posters have been placed at a wide range of locations such as entrance gates, reception areas and at restaurants. Please look out for these when you next visit Kruger and please let us know if you do spot any of these birds. Re-sightings of these birds initially provide us with an idea of the home-range of individual groups and will over time hopefully also provide an indication of movement of ringed between groups, especially in the case of evicted females which often leave their natal group when approaching adulthood.
Colour-ringing a SGH nestling
The poster requesting reports of re-sightings
All of the information gathered will assist us in getting to know these birds better and to hopefully make better-informed decisions in terms of their conservation and the re-introduction into their former range in South Africa. Another exciting recent development with regard to our work in Kruger is the registration of a PhD-project which will look at a range of aspects related to this species such as spatial use and criteria for nest-site selection. Such information learnt from the wild population will further assist and inform a range of decisions with regards to suitable sites for the future re-introduction of the species.
Here’s to hoping that the Bigblackblushingchicken remains part of the South African savanna- and grassveld-landscape and that the efforts of the SASGHAG partners assist in the species successfully repopulating a significant part of its former range in the country.