Spring time again

The knobthorns are in full bloom again, heralding in a new season of hope and expectancy. Among over seventy species of Acacia in South Africa the Acacia nigrescens, in the lowveld, probably gives as good a show as the yellow flowering species in other areas. I have mentioned them previously but would like to draw attention to the variation in flower colour.

Many of our trees have flowers that vary in colour, particularly the white ones with pink individuals and the blue or purple ones with white mutations. The usual flower colour of the knobthorn is cream, with flowers opening from spikes of reddish buds. Certain trees have particularly ‘lemon’ coloured flowers and on closer inspection you will notice that these lighter coloured flowers are opening from green coloured buds. The bud colour appears to vary from red, through a khaki colour to bright green.

It is a genetic variation that makes what might seem monotonous colouration just that little bit more interesting.

FOOD FOR BIRDS AND INSECTS

Acacia blossom does not produce much nectar for birds but enough for numerous insects which conduct most of the crosspollination. Go-way birds and monkeys, among other species, feed on the buds and the attendant insects provide a good feeding ground for many insectivorous birds. When they have young, even seed-eaters and nectar feeding birds will feed their chicks on a high protein diet of insects.

WILD COTTON

I have previously mentioned some of the variety of nesting materials, including spider web, used by different species of birds. Nest building is controlled by the availability of these materials. The varieties of ‘wild cotton’ form an important source of nest material for many species. The true wild cotton belongs to the genus Gossypium of which there are three species in South Africa - (G. herbaceum - which is a scrambling shrub. G. hirsutum - which produced useful cultivars, and Gossypioides kirkii with less woolly seeds). The genus is restricted to the north and east in South Africa and it was in this area and in central Africa where the first plants for cultivation were discovered.

Also restricted to the north and east of South Africa is a creeper - Ipomoea albivenia (climbing kapok) - which produces a slightly less woolly cotton. The white flowers are prominent when they climb over trees and shrubs. The cotton-covered seeds persist for many months and are probably helped in their dispersal by birds taking the cotton fluff for nest building.

COTTON NESTS

Many species of birds line their nests with wild cotton - mousebirds, certain sunbirds, canaries and warblers. There are certain species that use wild cotton as the main nest construction material.

The penduline tits weave an amazing little nest that looks like a little bag of white felt, while the Marico sunbirds use the cotton in a more coarse form to construct their white nests. It is interesting that the tits and Marico sunbirds (Nectarinia mariquensis) - which are one of our rarer sunbird species - have almost the same distribution in the northern and eastern areas as the plants they use for nest building. The benefit of a prominent, white nest is not clear.

Although they may reflect heat they appear Acacia nigrescens with green buds and 'lemon' flowers Acacia nigrescens with reddish buds and cream flowers Ipomoea alba (Climbing Kapok - Wildekatoen) 'Knob-thorn' (Acacia nigrescens) in flower Marico sunbird female on 'wild cotton' nest - feeding its young Marico sunbird male feeding chick with insect to be an easy target for predators - despite a slight effort at camouflage by the sunbirds.

CONSERVATION

With such reliance on a particular nest material, we have a good example of the dependency of one species on another - and there are numerous others. We have been fortunate, up to now, not to have had many veld fires in the agricultural and game farm areas this year. If there had been fires the wild cotton and other nest material would have been destroyed and certain bird species, like the Marico sunbirds, would not have been able to breed. Always bear in mind the likely ripple effect on other species before you carry out any action. Environmental network gets database manager

The Phalaborwa-based Ndlovu Node of the South African Environmental Observation Network (Saeon) has recently gained an information manager in the form of Nicola Stevens, who will begin the important process of developing the GIS (Geographical Information Systems) database that is an integral component of Saeon’s mandate to collect long-term environmental data. Stevens has a master’s degree in evolutionary biology and ecology, and has worked for the CSIR and Global Vision International. She attained her master’s degree studying buffalo in the Hluhluwe- Umfolozi Game Reserve as part of the reserve’s bovine tuberculosis research project. According to Saeon’s head, Johan Pauw, among her first tasks will be sourcing digital maps that are pertinent to the node’s savanna ecosystem in its focus area of the lowveld.

Many digital maps of things like geology, landuse, infrastructure, demographics and other biological information already exist, but in many different locations. As part of their mandate, Saeon will bring all these together into a single comprehensive database, and will make the information in the database available to policy makers as well as other interested parties. As Saeon has a strong networking focus, the data will be sourced from both private and governmental organisations, and Pauw is positive about the connections that Saeon has already developed, both in the lowveld and across the nation. A new manager for the Ndlovu node has yet to be appointed, after previous manager Dave Balfour left to take up the position of head of scientific services for Eastern Cape Parks