Invasive house crows, mallard ducks and guttural toads

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The City of Cape Town has three management programmes for invasive animals that threaten the existence of local species.

House crows

There are 2 million house crows (Corvus splendens) in Dar-es-Salaam, where they are a major problem for local authorities. This invasive species has spread south from East Africa into the metropolitan areas of Cape Town, Durban and Richard’s Bay. The Cape Town population is the most southerly recorded population and has the potential to spread from here to the West Coast of Africa. Read more...

House crows are aggressive and opportunistic feeders and have negative impacts on indigenous bird and animal populations, agricultural crops and domestic poultry. House crows also pose a threat to human health, as they are intestinal carriers of at least eight human enteric diseases.

In 2008, the Cape Town population was estimated to be in the range of 10 000 birds and urgent measures were needed to prevent the number from increasing further. The City launched an intensive eradication programme in partnership with BirdLife SA, the National Resource Management (NRM) Programmes and the South African National Biodiversity Institute (SANBI), which all meet under the auspices of the National Problem Bird Forum, which is chaired by the Endangered Wildlife Trust (EWT).

The aim is to complete eradication by 2017. Thereafter an EDRR programme will be implemented to detect and remove any new arrivals before they establish.


Guttural toads (Amietophrynus gutturalis) pose a serious threat to the survival of our endemic, endangered western leopard toad (Amietophrynus pantherinus), as they compete for habitat, resources and breeding grounds. Read more...

Guttural toads were found in Constantia in 2005 and currently occur in about five square kilometres in the Constantia Valley area, where they are known to breed in garden ponds. If this population is allowed to continue spreading along the greenbelts there is a very real threat that they may in future colonise all major Cape Town water bodies, with potentially disastrous consequences.

Guttural toads are easily confused with the endemic leopard toad and the public is urged not to remove any toads, but rather to contact the Invasive Species Unit if they suspect that there are guttural toads in their gardens.

Mallard ducks

The City of Cape Town follows the National Mallard Strategy for South Africa. According to Professor Phil Hockey of the Percy FitzPatrick Institute of African Ornithology, the mallard is a relatively recent colonist and appears to be in the early stages of a large scale invasion. Hockey regards the mallard as the most threatening invasive bird species in the country today. Read more...

To implement the country’s mallard strategy, Cape Town’s Invasive Species Unit works closely with BirdLife South Africa, the Western Cape Invasive Animal Working Group, National Resource Management (NRM) programmes, Ezemvelo KZN Wildlife and the South African National Biodiversity Institute (SANBI) – which all meet under the auspices of the National Problem Bird Forum, currently chaired by the Endangered Wildlife Trust (EWT).

Mallard hotspots in Cape Town include Marina Da Gama (where there are an estimated 800 mallards), Sonstraal Dam in Durbanville and water bodies on golf courses and housing estates across the city.