Eagles brought in to clear soiled greens for golfers

Heads up! The hawks are coming. Like the priority-crime investigators, the Harris hawks are an elite unit — but instead of capturing crime bosses, they have been trained to strike at nuisance birds.

These include indigenous Egyptian geese, which are rapidly expanding their range in Cape Town and other cities. The geese breed fast, steal the nests of other indigenous birds and foul green spaces like golf courses and sports fields.

When the hawks were let loose at Rondebosch golf course in Cape Town to spread fear, the geese became 76% more vigilant — shown by putting their heads up to look around in case a raptor was flying in — and their numbers declined by 73% on the property.

In contrast, between June 201 and January 2015, geese numbers rose from 208 to 297 at Steenberg golf course and from 211 to 280 at Westlake, where no hawks were flown.

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Conflict between wildlife and people is increasing globally, and methods to control "problem animals" range from killing them to non-lethal techniques, which often have a limited impact, because the targets get wise to them.

Dr Arjun Amar, co-author of a paper on the effect of the hawks' scare tactics in Rondebosch, said: "We used the fear of raptors to dissuade the geese from occupying a golf course in large numbers.

"The method was not entirely non-lethal. Some geese got killed by the hawks, but the numbers which left were almost three times greater than the numbers killed."

Predator birds are used in cities around the world to reduce "nuisance birds" at airports, garbage sites, factories, stadiums and even at Wimbledon.

But until this experiment, nobody had tested how effective this method was, said Amar.

For it to work, the hawks create a "landscape of fear", which means the geese cannot concentrate on feeding.

Amar said: "It is a bit like us: we would rather be foraging for food in a place where they are no lions around."

To reinforce the threat, the trained predators — which are indigenous to the Americas — were flown from inside a golf cart, which became the bogeyman for the geese.

"Suddenly the hawk explodes out of the golf cart and the geese learn to associate golf carts with danger. They don't know which golf cart has a huge predator going to come out and attack them.

"The buggies are driving around all the time, and this reinforces the threat over and over," said Amar.

However, unless the hawks keep swooping out of buggies, the Egyptian geese return to the site, and two months after the trial their numbers were up again.

City of Cape Town mayoral committee member Brett Herron said the council had no control programmes for Egyptian geese, although he acknowledged they could be a nuisance.

"Managing parks or water bodies to reduce grass cover, in particular the water-grass interface, and planting indigenous species such as reeds, does help," he said.

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Africa's black sparrowhawks start breeding earlier in the city and build multiple nests to avoid conflict with the geese, which sometimes seize their nests.

The city's invasive species unit gets complaints regularly about Egyptian geese, hadeda ibis, guinea fowl, the common peacock and pied crows.

Predator birds are also used in Durban to control nuisance birds, but a few years ago there was a public outcry when the Royal Port Alfred Golf Club applied for a permit to shoot 100 geese.

Egyptian geese are not the only species that thrives in urban areas. Certain predators do too. Cape Town has about 50 nesting pairs of black sparrowhawks and about 50 pairs of peregrine falcons.

The research on how the trained Harris hawks chasing the geese to safer, greener pastures was published in the February issue of the Journal of Wildlife Management.

Lead author Dr Alex Atkins, Amar and the two other co-authors are based at the University of Cape Town's Percy FitzPatrick Institute of African Ornithology.