By John Yeld
Environment and Science Writer
A pilot programme to eradicate the invasive alien House Crow from the Peninsula has proved highly successful, with about one quarter of the estimated 10 000-strong population eliminated in the past few months.
The predatory and scavenging crows, which feed on carrion and store food in places such as the eaves of houses, carry diseases including cholera, salmonella and entero-amoeba.
They also target indigenous bird species, robbing their nests and killing their chicks.
Louise Stafford, the City of Cape Town's invasive alien species co-ordinator, confirmed that they had conducted eradication trials during December in partnership with a service provider, the Nature Conservation Corporation, in preparation for the formal registration of the avicide poison, Starlicide.
This poison is widely used for problem birds, but is strongly opposed by some animal welfare groups, including the SPCA.
Stafford said the trials had involved testing the efficacy of bait and baiting methods, and that she hoped the avicide would soon receive emergency registration, after a 13-month battle.
She was responding to recent messages on the local birders' Internet forum, capebirdnet. One of these messages was posted by Gerald Wingate, who asked this week: "Where are the House Crows?
"While (bird) atlasing in Goodwood, I searched all around the N1 City Mall for the House Crows that have been there for years," he wrote.
"I also looked for them in Bothasig - no sign of them. I know that an eradication programme has been initiated - has it been so successful that the HCs in N1 City area have been eliminated within two weeks?"
Stafford said mass baitings had been conducted in Bothasig, Milnerton, Epping, Woodbridge Island, N1 City area, Nyanga and Woodlands.
"We also conduct weekly baitings at the airport and surrounding areas - for obvious reasons."
The bluegum trees that had served as the birds' main roost in Nyanga were trimmed, which resulted in the crows forming satellite roosts in various parts of the city, she explained.
"The strategy is now to conduct mass baitings at pre-identified satellite roosts, and to prevent the crows from moving inland. The furthest known sightings were Milnerton, and we addressed those. Recent reports of House Crows in the Stellenbosch area are not yet confirmed."
Other areas where crow numbers had been reduced to zero were Mandela Park and the Nyanga Clinic, Stafford added.
"We noticed they repopulate areas following successful baitings within two months. This trend is addressed through ongoing monitoring, and when the repopulation occurs, we follow up with a mass baiting."
Stafford said it would be of huge value to the project if bird club members reported House Crow sightings in areas surrounding the city, such as Milnerton, Melkbosstrand, Atlantis, Somerset West, Stellenbosch, Durbanville, Wellington and the far south peninsula - Fish Hoek, Noordhoek and Hout Bay.
"We know where they are in the areas closer to the Cape Flats, but need eyes on the ground - or in the air - in the areas where they are not known to occur."
They are native to India and were introduced to East African ports such as Mombasa and Zanzibar, where they are now a major pest.
They gradually made their way down the coast, reaching Durban in 1972, and Cape Town in the early 1980s.