Somewhere between one and two million Indian house crows are estimated to live along the Kenyan coast and they are migrating deeper into the country. Kenya’s neighbours in East Africa and beyond are also plagued by the species, with several also resorting to poison.
“It is high time this invasive species was eradicated to stop the cumulative negative ecological and social effects of this species along the east African coast,” says John Musina, an ornithologist and conservationist with the National Museums of Kenya.
Wildlife officials in June described the crows as “invasive alien birds that have been a nuisance to the public for decades, significantly affecting local bird populations by driving them from their natural habitats”.
The crows, known to scientists as Corvus splendens, are native to much of South and South East Asia. The slender, glossy black birds, grow to around 40cm (16in) have large beaks and lighter grey “collar”.
They have spread further afield either on ships, or by being deliberately introduced in the belief they would help manage rodents and rubbish.
‘Aggressive and opportunistic’
The crows were brought to the nearby island of Zanzibar in the 1890s to help tackle a mounting waste problem in what was then a British protectorate. They then spread along the coast and were first recorded in Mombasa in 1947.
In all, they are thought to have found their way to as many as 36 countries outside their native range.
While in Asia they are held in check by monkeys, snakes, birds of prey and rival crow species, in their new homes, they appear to have no natural predators, according to the Global Invasive Species Database (GISD).
Conservationists blame the crows for significantly reducing the number of small indigenous birds, such as weavers and waxbills, by ripping their nests apart while targeting eggs and chicks.
Dr Mwenda Mbaka, an expert in veterinary public health and pest control, said: “House crows are aggressive and opportunistic feeders. They feed on the eggs, chicks and even adult birds of native species, leading to a decline in local bird population.”
Small reptiles, mammals and invertebrates also fall victim to the crows and their habit of preying on chicks and eggs plagues free range poultry farmers by preying on chicks and their eggs.
House crows also carry at least eight human diseases in their guts, though the GISD says that a link with the spread to humans is yet to be established.