Nyika-Vwaza Transect

Explanation: In May and June of 2002, my wife and I found ourselves exploring some remote natural areas of northern Malawi in east Africa.

After spending time in the amazing high country grasslands and woodlands of Nyika Plateau, we did a drive to Vwaza Wildlife Reserve.

The drive took us from the Nyika highland elevation of 7100 ft (2164 m), down through numerous life zones and ecosystems, to the wetlands of Vwaza at 3420 ft (1042 m).

En route, we stopped many times, and I kept track of the changes in trees and birds, and marked the elevations of those changes.

This week's main image is a summary of my observations on this Nyika-Vwaza Transect.

Here is the extent of the transect, starting at the high plateau at
point A (upper right), winding through steep mountain country
of evergreen forests, and woodlands of Brachystegia, miombo,
and acacia, and ending at the wetlands of Vwaza at Point B.
Click on the photo thumbnails for larger images,
and elsewhere on the map for a larger map image:

It was most striking how tied the birds were to the trees and vegetation along this transect.
For example, I found Red-tufted Malachite Sunbirds and Miombo Double-collared Sunbirds only in the Brachystegia woodlands above 6500 ft (1980 m) elevation, whereas most of the higher-elevation birds dropped out when we reached the miombo and mixed miombo-Brachystegia woodlands at about 5500 ft (1675 m). Of course, some bird species migrate across altitudes by season, so this was just a "snapshot" during the late May-early June period.
As we entered the acacia woodlands at 4000 ft (1220 m), suddenly appeared Marshall Eagles, Red-billed Queleas, Paradise Flycatchers, and Cardinal Woodpeckers. And at the base elevation of Vwaza Wildlife Reserve, a whole new suite of tree species appeared, including baobabs, monkey orange, African star-chestnut, marula, bushwillow, pod mahogany, and a wonderful tree named after the appearance of its large seed pods set within a flat disk, "hedgehog in a saucer."
Such observations can prove very important as baselines from which to compare later conditions cause by climate change. For example, if the local climate should trend toward regional increases in temperature, the first occurrence of some tree and associated bird species might be moving upslope to higher elevations. The directional trend and rate of such indicators could prove to be valuable for understanding the pace of changes in other parts of the ecosystem.
I am not aware of any study that has been conducted on the elevational ranges and co-occurrence of birds and trees in this part of Africa. Perhaps this little study can spur others to replicate the transect and discover different species and new relationships, and to monitor shifts over time in the face of climate change.

EPOW - Ecology Picture of the Week