Grain-eater species hit Cape Town

John Yeld
April 24 2009 at 02:22PM

The "feathered locusts" have arrived in the Western Cape!

That's the urgent warning ornithologists are posting to conservation and agricultural authorities after a ringing operation near Worcester this week confirmed the presence of a breeding population of red-billed quelea.

This grain-eating species is probably the most serious bird pest in Africa, sometimes occurring in flocks of millions of individuals which have devastating impacts on crops.

Control operations by agricultural authorities elsewhere in the country - particularly in the North West Province, Free State and Limpopo - and further afield in many African countries, kill several million at a time but do not make a significant dent in their overall numbers.

The estimated total quelea population is 1,5 billion birds, and it is considered by some to be the most numerous land-bird in the world.

There are real concerns that if it becomes locally established in the province, it could seriously reduce harvests of wheat and other grains, with agriculture already under pressure from climate change.

"This is the worst news since sliced bread, a real nightmare!" said Professor Les Underhill, director of the Animal Demography Unit in UCT's zoology department.

"If quelea get a grip on the Western Cape and start breeding here in the swarms that they occur in further north, they will become a major agricultural pest."

Agricultural practices such as the provision of livestock feedlots and water sources - especially grain feedlots on ostrich farms at places like Leeu Gamka - are believed to be encouraging this regional migration.

Underhill's colleague Dr Dieter Oschadleus, who is bird-ringing co-ordinator of Safring, says the red-billed quelea - one of 112 weaverbird species in the world - did not occur historically in the Western Cape but had in recent decades started expanding its range into the province.

"But there has not been any evidence of breeding in the winter rainfall region of the province - until now."

On April 6, Erna Rabie of Nuwerus farm between Worcester and Robertson noticed a flock of several hundred quelea, including males in breeding plumage, roosting in reeds on the Nuy river.

"The birds were still present a week later, so I decided to ring them," said Oschadleus.

On Monday and Tuesday he and birder Mike Ford set up nets, helped by members of the Worcester Bird Club.

Their operation found hard evidence that the quelea had bred recently: many nests and eggshells, two nests with addled eggs and a large number of juveniles.

"This is the first breeding record of the species in the winter rainfall region," said Oschadleus.

Of the 116 quelea ringed, 10 were adult males, nine adult females and 97 recently fledged juveniles.

"Quelea were present all day in the reeds, calling and resting, with individuals flying in and out to forage.

"The population is estimated to be a few hundred."

This reeding site in the Breede River Valley is not far from the Overberg wheat-growing area, Oschadleus added.

It was difficult to know what effect the queleas would have in the Western Cape and how well established they would become, he added.

"However, there is a good chance that they will keep increasing and start attacking wheat crops."

While quelea were sometimes blamed for damage they did not do - the birds were very visible, while insects were less so - they had certainly been proved to cause vast damage, he said.

"The most important thing is to keep monitoring them.

"Farmers should be warned, the Department of Agriculture should be informed and I will certainly contact the quelea group in Pretoria."

john.yeld@inl.co.za

This article was originally published on page 8 of Cape Argus on April 24, 2009

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