They are one of Africa’s most loved birds, with graceful aerial skills, distinctive plumage and an unmistakable call that shatters the dawn quiet over lakes and rivers.
The future once looked bleak for the African fish eagles at Lake Naivasha — one of the bird’s previous strongholds.
In 1996, conservationists recorded just 67 individuals living around the lake and there were fears that pollution from the flower farming industry, growing population and other environmental pressures would destroy a once abundant ecosystem.
Now though, the fish eagle population has recovered to around 240 — close to the numbers seen in the lake’s wildlife heyday in the 1960s.
This remarkable conservation story is the subject of a beautifully shot two-part documentary called Resilience: Fish Eagles of Naivasha, which airs on NTV on Wednesday.
“The African fish eagle is one of the most charismatic birds in Africa,” says Mr Munir Virani, global director of conservation strategy with Peregrine Fund, who made the film, which was supported by Aga Khan University’s Graduate School of Media and Communications. He has been studying the birds at Lake Naivasha for 23 years and has documented the fish eagles’ remarkable comeback.
The lake is still under intense environmental pressure from human activities, but efforts to clean up pollution and mitigate some of the worst impacts appear to have borne fruit, at least for the fish eagles.
ADAPTABLE BIRD OF PREY
“The African fish eagle is a very adaptable bird of prey. Because they are generalist feeders (they feed on a multitude of things) and are tolerant of human activity, they generally do well even when conditions are not ideal,” said Mr Virani. When fish numbers in the lake have dropped, the eagles vary their diet by taking water birds and even feeding on dead animals on the lake shore.
The bird has also benefitted from the arrival in 2001 of an invasive fish — the common carp. It has caused ecological havoc by outcompeting many other fish species, as well as eating their eggs and disrupting their nests on the lake bottom. But the fish have provided an abundant source of food for the eagles.
It is this flexibility that has allowed the birds to adapt to the profound ecological changes that have impacted Lake Naivasha in the past half century. One concern is pollution from pesticide runoff from the burgeoning flower industry on the lake’s shores.
Prior to the insecticide DDT being banned, it was having a significant impact on many bird species — including the African fish eagle — by interfering with reproduction.
Once taken into the birds’ bodies via food, it prevents the shells of their eggs forming correctly. These extra-thin shells are liable to crack, meaning that many chicks do not survive.
Masumi Gudka, of the Birdlife Africa Secretariat in Nairobi, has studied DDT levels around the lake.
“Lake Naivasha is a hub for floriculture-horticulture activities, so there’s been a lot of concern over how those practices are being run and how they are affecting the lake and the biodiversity around it,” she told the documentary-makers.
Although she found DDT in all samples collected from around the lake, the levels in the fish eagles blood have dropped considerably compared with previous
measurements. “[It] was nowhere near where it used to be in terms of causing eggshell thinning and impairing reproductivity. They were very low levels,” she said.
Some of the credit for the improvement, says Virani, should go to Lake Naivasha Growers Group, which represents about half of the flower farming industry in the region. Encouraged to act by Imarisha Naivasha — a government initiative set up in 2011 to bring together lake users and the local people to improve the health of the lake — the farms have introduced measures to limit the amount of pesticides, keep them contained on site and reduce water use.
“Most of the growers now have adopted closed system hydroponics which means that any excess water in the greenhouses is usually recycled for reuse” says Joseph Kariuki, chief executive of the Lake Naivasha Growers Group.
Perhaps the most profound threat to Lake Naivasha are the sheer numbers of people now living around it. Sewage flows into the lake without being treated and overfishing is a big problem. It will take a huge effort to ease the environmental strain.
‘Resilience: Fish Eagles of Naivasha’ airs on NTV at 10pm on Wednesday evening.