Why do some birds collide fatally with power wires? This question is an especially important one for South African ornithologists and conservationists. Here there are a number of larger birds species that live in open habitats, such as in the Karoo and the farming areas of the Overberg, whose populations now seems threatened by the scale of power wire collision deaths. Among these species are the endangered Blue Cranes (the national bird of South Africa) and various species of Bustards. Graham Martin recently spent three weeks in South Africa working with Jessica Shaw from the Percy Fitzpatrick Institute of African Ornithology at the University of Cape Town, as the guest of the Endangered Wildlife Trust. They were looking into the vision of these birds with the aim of understanding why cranes and bustards are so prone to collisions. They found that compared with many bird species the frontal vision of both cranes and bustards is particularly restricted; suggesting that in flight they are often unable to see anything ahead. Thus no matter what may be attached to power wires to make them more conspicuous, the birds may simply not see what is ahead. Full analysis of this preliminary data will be reported to the power generation company Eskom, who are responsible for the power distribution network, with the hope that a solution can be found to this problem, especially in key areas where collision rates are high.
Photos: Top Blue Crane Anthropoides paradiseus, Bottom Kori Bustard Ardeotis kori
