Power line peril for terrestrial birds in South Africa
In a tracking project by BirdLife South Africa since 2011, eight out of 13 young secretary birds have perished, several after colliding with power lines and fences.
“This highlights a scary reality that recruitment of young birds into the breeding population is very low and could spell future disaster for South Africa’s secretary bird population if urgent steps are not taken,” said Dr Melissa Howes-Whitecross, the acting terrestrial bird conservation programme manager and raptors and large terrestrial birds project manager at BirdLife South Africa.
Kwezi, a 6-month-old secretary bird, was tagged in February as part of a secretary bird conservation project on a farm near Besters in KwaZulu-Natal.
In February, Kwezi was fitted with a tracking device at the age of around 8 weeks.
“She showed the typical developmental pattern of the previously studied secretary birds, exploring the environment around her natal nest in ever increasing distances,” said Howes-Whitecross.
On July 23, Kwezi set off on her first major dispersal flight away from her nest and by July 25, she had travelled approximately 26km from her natal nest. Dispersal means that a young bird is capable of fending for itself.
“Unfortunately, she would travel no further after she collided with the overhead cables of a large electrical transmission line.”
BirdLife SA selected the secretary bird as its Bird of the Year for 2019 and has been trying to profile the conservation concerns facing these charismatic, long-legged birds who are apex predators in the open grasslands and savannahs of sub-Saharan Africa.
“Southern Africa’s secretary bird population is in trouble and urgent steps need to be taken to ensure that these regal birds which stride across the African grasslands do not become another statistic of lost biodiversity in the ever increasing global crisis,” it said.
Recent studies have shown declines of between 70%-80% of secretary birds across southern Africa.
The tracking project started in 2011, after which 10 juvenile secretary birds were fitted with lightweight solar-powered, GPS-GSM telemetry devices between 2012 and 2014.
Over 45900 location points were collected and the “groundbreaking” findings have improved the understanding of the movements, dispersal and survival of juvenile secretary birds.
“Unfortunately, a darker side of the telemetry study has been the reports of mortalities of several of the young tracked birds,” said BirdLife SA.
“Fences and power lines are a considerable threat to young raptors and large terrestrial birds, in particular secretary birds.”
Ernst Retief, who previously co-headed the tracking project, and who is working to understand and mitigate the impacts of fences on wildlife, said: “It’s likely we’re vastly underestimating the detrimental impacts infrastructure such as fences and electrical cables are having on our terrestrial birds.”
Howes-Whitecross, who took over co-ordination of the project in 2018, has since fitted telemetry devices to three additional juvenile secretary birds, two of which have already been lost to collisions with high-voltage electrical cables, including Kwezi.
Tambo, a young secretary bird rescued from the edge of the OR Tambo International Airport runway after suffering from a severe foot infection, was rehabilitated by the Johannesburg Wildlife Veterinary Hospital for four months and released in the grasslands of Devon, Gauteng.
He died after colliding with electrical infrastructure just four weeks after being released in October last year.
BirdLife SA has reported Kwezi’s collision incident to Eskom and the Endangered Wildlife Trust.
“Kwezi’s death will hopefully result in the marking of the power line, to prevent further mortalities. The attachment of bird flight diverters will increase the visibility of the lines and deter birds from colliding with them in future.”
Secretary birds, other raptors and large terrestrial birds are already under pressure from high levels of habitat loss across the region.
“This, coupled with the high mortality rates of young secretary birds, is a concerning factor when considering their long-term survival and conservation,” said Howes-Whitecross.
“If young birds are not making it successfully into the breeding population we will see the knock-on impacts of this with a future population crash.”