African Wildlife Environment Issue 75 FINAL

FAUNA, FLORA & WILDLIFE

Over the next 15 years I researched that question. My basic assumption was that the abundance of a wild species was proportional to the degree to which its living requirements were met. All I had to do was see where my birds were common and where they were scarce and then figure out the relevant habitat differences. I used bird dogs as my field assistants and we chalked up number of birds found per minute searching in habitats varying in geological substrate, elevation, landscape type, and years since last veld fire. My birds were commonest on veld burnt in the last year. They were scarce or absent in overgrazed and over-rested veld. Recent veld burning history explained a lot. My birds lived largely on the underground storage organs of forbs, dug up with their bills. Rank grass, arising from absence of fire and grazing, suppressed leaf-production and flowering of the forbs, as Bayer had said, and the birds surely used the above-ground plant parts as a guide as to where to dig. Besides, the birds lived on the ground and for them to get through thick grass was akin to us in a bamboo forest.

Another striking finding was that in my study area – Giants Castle Game Reserve – Greywing Francolin occurred only above the 1940 masl contour, whereas Redwing Francolin occurred above and below that elevation. The 1940 masl contour was a tortuous line. Why did Greywing follow it so exactly? It coincided with the interface between nutrient-poor Karoo sedimentary rocks below and nutrient-rich Drakensberg basalt above. Why should nutrients be so important to Greywing and seemingly not to Redwing? I found Greywing to be typical phasianids (fowl family). They had short small intestines and ate small volumes of high-quality food. Of course, Greywing occur below 1940 masl elsewhere, and can be found over base-poor sedimentary rocks, but wherever I have encountered them they are short-gutted and eat small volumes of quality food. Redwing on the basalt, above 1940 masl, behaved the same – standard phasianids eating small volumes of high-quality food needing only a short gut to digest it. But on the base- poor severely weathered Karoo sediments below 1940 masl Redwing ate large volumes of low-quality

If fire is kept out, grass accumulates and then when a fire does occur it burns intensely with grass tuft mortality (picture center) and even mineralization of the soil

In the long-term absence of fire the dead grass suppresses leaf and flower production of the non-grass herbs, like this iris

My birds were not alone in their preference for recently burnt veld. They were simply members of a community of plants and animals dependent on recurrent veldfire. In comparing francolin abundances on recently burnt with long-since burnt veld I was struck by the coincident effects on other birds and on antelope. My colleague, Dr David Rowe-Rowe, identified the same response in small mammals – their numbers and diversity increased after veld fire, but after a couple of years, in the absence of fire, declined.

food and had enormously long intestines. The low- quality food was compensated for by consuming larger volumes and by prolonging the digestion time with a longer gut. This was an intriguing adaptation by Redwing. It enabledthemtooccupyextensiveareasoflandwithout competition from Greywing. It was another lesson for me in the importance of nutrients in the world of wildlife. As ecologists say, phosphate (P) is often limiting on ecosystem function. Most of the oceans of the world are wet deserts, for want of P. In contrast, in the upwelling zones, like our west coast, the sea is enriched and we have rich fisheries. With my interest

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