The rare bird that could reveal whether Botswana’s Okavango Delta is in trouble
· The South African
A rare waterbird in Botswana’s Okavango Delta is giving scientists an unusual way to monitor the health of one of Africa’s most important wetland ecosystems.
The vulnerable slaty egret is found only in southern Africa, with its range centred on the Okavango Delta and nearby floodplains in the Okavango and Zambezi river basins.
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According to UNEP, the bird’s limited range makes it particularly important to conservationists trying to understand what is happening to the region’s wetlands.
Why scientists are watching the slaty egret in the Okavango Delta
The slaty egret is a long-legged wading bird that depends on wetland habitats for food and breeding.
Sergey Dereliev, Executive Officer at the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA), said the bird is endemic to southern Africa and is only found in the Okavango Delta and some adjacent floodplains.
That makes the species closely linked to the health of the wetlands where it lives.
Monei Onalethatai, Senior Wildlife Biologist at Botswana’s Department of Wildlife and National Parks, said the slaty egret is particularly sensitive to environmental disturbances and changes to the ecosystem.
“Whatever happens in the ecosystem will necessarily reflect in the distribution and the presence of the bird,” Onalethatai said.
In other words, changes in where the birds are found could provide scientists with an early indication that conditions in the wider ecosystem are changing.
A warning sign for the Okavango Delta
The slaty egret is not important simply because it is rare.
Researchers are also interested in its population, breeding success and distribution because these can provide clues about the condition of its habitat.
An international conservation plan for the species identifies the need to monitor its population and trends, protect important breeding and roosting sites and ensure sufficient food supplies.
The plan also highlights potential pressures including disturbance at breeding colonies, changes affecting water quality and availability, habitat degradation and pressure on fish populations.
The wider Okavango system faces pressures that extend beyond Botswana’s borders. The Delta is part of a larger river system involving Angola, Namibia and Botswana, making regional cooperation important for protecting its wetlands and wildlife.
Climate change adds another challenge
Climate change is among the pressures identified by AEWA as affecting waterbirds, alongside changes to hydrology, agriculture, infrastructure and other human activities.
For the Okavango Delta, changes in water availability and the timing and extent of flooding can have consequences for the plants, fish, birds and mammals that depend on the wetland.
That is why monitoring a species such as the slaty egret can provide information that goes far beyond one bird.
Botswana’s Okavango Delta is one of Africa’s most important wildlife destinations, supporting hundreds of bird species as well as large populations of mammals and other wildlife.
For scientists, the slaty egret could therefore serve as an important piece of the puzzle.