Alien Crows Targeted for Total Extermination in S. Africa

Leon Marshall in Johannesburg
for National Geographic News
May 9, 2006
South Africa's environmental authorities are preparing to wipe out the
country's entire population of alien Indian house crows.

The invasive crows arrived about five decades ago and have become such a threat to local bird species that officials say the only option is to kill them all.

"If successful, it will be the first time we have succeeded in eradicating an entire alien species," says Guy Preston, a specialist on invasive species for the South African government and leader of the campaign.

He says the crow, whose home range reaches from Iran to Pakistan and India, is a particularly aggressive species and a scavenger. It kills and drives off other birds until it is the only bird in its range, posing a serious threat to South Africa's biodiversity, Preston added.

The alien bird is smaller than South Africa's native black crow. The house crow keeps to urban and suburban areas, where it tends to nest in buildings and roofs.

The worldwide spread of bird flu has become an additional concern, given the crows' habit of scavenging in chicken coops, preying on eggs and chicks.

"We just have to get on top of them. If we don't, it will have catastrophic consequences for our biodiversity, and it will endanger people because of the diseases they carry," Preston said.

Poisoned Food

Attempts have been made before to exterminate the birds, but these efforts failed mainly because of a lack of funds.

This time sufficient money has come from the Washington, D.C.-based Global Environmental Facility, the United Nations Development Program, and the South African provincial governments, whose port cities of Durban, Port Elizabeth, and Cape Town have been invaded by the species.

(See map of South Africa.)

"Once we have eradicated [the crows] … we'll have to protect our frontiers and monitor shipping to see that they don't come here again," Preston said.

Louise Stafford, coordinator of the program for the Western Cape Province, says the extermination will be done during the first four months of next year. That is when the birds congregate after having paired off to breed from September to December.

But preparations for the project have already started. Sites where the birds congregate are being identified. The sites will then be baited with food laced with lethal doses of anesthetics that will put the birds to sleep before they succumb.

Gerhard Verdoorn, director of the conservation group BirdLife South Africa, supports the extermination program. "They are an utter menace," he says of the crows.

"The intention behind the mass euthanasia project is to get rid of the birds in the most humane manner possible and in a way that should not pose a threat to any other birds or animal life," Verdoorn said.

"Trying to shoot them has proved futile. They are too cunning. The moment they hear the first shot, they are gone."

Public Concern

The food will be poisoned with starlicide, alpha chloralose and chloral hydrate, chemicals that are normally used in smaller dosages to tranquilize birds.

Other birds are unlikely to be endangered by the poison, Verdoorn says, because the house crows drive them away from their feeding places.

Aware of the likelihood of public concern, birding clubs affiliated with BirdLife South Africa will launch information campaigns to ensure people know what is being done and why.

Stafford, the provincial coordinator, says the public response so far has been encouraging. Rather than objecting, people have been calling to pledge support and offer assistance.

"People generally seem to understand the danger this species poses for our indigenous birds. And they breed so fast, we simply cannot do nothing about them," she says.

The project has the support in principle of South Africa's Society for the Prevention of Cruelty to Animals (SPCA), although its senior inspector, Rick Allan, says there are still two issues that need to be cleared up.

"We know these birds are problematic, but we have asked for a detailed justification for their extermination," he said.

"The other issue is the methodology. We want to make sure about the poison used and that it is indeed the most humane method of killing the birds.

"But we support the project. It is just a matter of formalizing matters," Allan said.

Backers of the program point out that they can even find support in the birders' guide book Roberts Birds of Southern Africa.

The book describes the house crow's feeding habit as creeping "silently through undergrowth in search of birds' nests" and killing and eating adult birds.

On the topic of house crow conservation, the book bluntly declares, "Successful and destructive alien; eradication measures are warranted."

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