Raptor numbers plummet, and the race is on to find out why
Even in highly protected areas like northern Botswana, these iconic birds have alarmingly decreased
Many birds of prey are vanishing from one of Africa’s last great wildernesses, say University of Cape Town ornithologists.
A team from the Fitzpatrick Institute of African Ornithology, which re-created part of a survey completed more than 20 years ago, said it was shocked by what it found in northern Botswana.
“Although declines in raptor populations have been seen elsewhere in Africa, particularly across west Africa, we were not expecting these declines to be quite so dramatic in Botswana, which has a relatively low human population size and where nearly 40% of the land is under some form of protection,” said project supervisor Arjun Amar.
“Species declines were detected for 14 out of 29 species monitored. Eleven of these species declined by over half in the last 20 years.”
Sightings of iconic species of eagle and vulture declined by up to 80%, and some migrant species recorded last time have vanished, according to the study published this week in the journal Biological Conservation.Researchers spent two years driving more than 20,000km, repeating part of a journey undertaken in the 1990s by Marc Herremans, a biologist for Botswana’s wildlife and national parks department.
They retraced Herremans’s route on gravel and tar roads in a similar vehicle to the one he used and driving at the same speeds. In line with the original survey, they spotted birds with the naked eye, only using binoculars.
Amar, whose team conducted the study with conservation NGO Raptors Botswana, said some of the species showing the greatest declines are the white-headed and lappet-faced vultures, African hawk eagle, secretary bird, bateleur eagle and red-necked falcon. Only three species increased: brown and black-chested snake eagles and the tawny eagle.
Beckie Garbett, a PhD student who led part of the roadtrip, said: “We found declines occurring across species with varying diet and habitat use, which make it hard to pinpoint the main drivers of decline.
“Climate change is one candidate for these declines, but urgent research is needed to better understand the drivers of these declines.”
Herremans said he was pleased his data had proved valuable, but added: “It is sad, though, to learn that even in this country with so much of the land devoted to conservation, biodiversity is in steep decline.”
Conservationists say vultures, in particular, are vulnerable to poisoning by poachers for whom the birds’ habit of circling carrion is a threat because it draws game-rangers’ attention.
Another recent study found a third of all vultures caught and tested in a separate Botswana study had elevated levels of lead in their blood, probably due to ingesting bullet-contaminated flesh.