The New Zealand Falcon is a threatened bird species. Its range and territories have shrunk with settlement and horticultural development. Mammalian predators now take eggs and chicks from the ground nesting sites cats, pigs, possums, even hedgehogs.
The falcon has a trusting nature and can be approached by humans for tagging and fitting of transmitters. It will also adapt to man-made, predator-proof nests on rocky bluffs or in trees. They will sit nearby to vineyard workers, who enjoy their company. Males are one-third smaller than females.
In other parts of the world falcons are used to patrol vineyards and airfields.
Techniques for artificial insemination, incubation, rearing chicks and successfully transferring young birds to new nest are well-established.
The falcon is a visible stimulus and its body form is innately recognised by birds with a fear response. It then sensitises the prey and reinforces this response. It does this by attacking the prey. The prey starts to flee, and has several seconds of fear reinforcement. Depending on the skill of the falcon and the vulnerability of the prey, maybe only 10% are caught; 90% escape, having learnt a lesson.
In addition, any other prey birds that witnessed the incident, even though they were not themselves attacked, also learnt from the experience. So the deterrent is reinforced quickly across all the prey. Soon the prey birds will tell each other if a falcon is about. They will start making alarm calls, sensitising the other birds that are busy feeding and cannot see the falcon. So the effect of the falcon, rather than diminishing, is magnified.
Conceived by UK raptor researcher Nick Fox, who did his PhD in NZ in the 1970s, the Falcons for Grapes five-year project is funded by Sustainable Farming Fund and Marlborough Wine Growers Association.
The intention is to boost the now almost non-existent falcon population on the Marlborough Plains so that the falcons will control the other birds, like starlings, which attack near-ripe grapes.
Two males and two females have been taken as fledglings from the wild and reared in artificial nests in two vineyards. They are fed daily, eating day-old chicks and road kill. They also catch their own prey, such as mice and small birds. They carry transmitters in a back-pack with batteries which last about six months. Their movements can be tracked for 1km on the flat, but on higher ridges could reach 5km. In practice they are staying within 2km radius.
Project manager Colin Wynn is getting a sight of the four birds each day, and they have established territories, which they will defend. Now the young males and females have paired off, one pair on each of the two project vineyards.
Next year it is hoped to introduce GPS tracking, with 10 second intervals, to that flight paths can then be mapped on computer, giving the vineyard owners a record of when and when falcons have been patrolling. They fly overhead and down the rows, underneath the wires and foliage, to chase little birds. This is their natural diet, but most of the time they are unsuccessful in catching, except to scare the smaller birds out of the vineyards into the open.
Once the falcons are established, they will be on show for visitors, but until then one of Colins jobs is to keep them secure, well-fed and undisturbed. The managers of the vineyards say the falcons have been effective in displacing the flocks of starlings to un-patrolled areas.
- Falcons will replace some of the need for more aggressive bird scaring like shooting and gas cannons, which are environmentally unattractive.
- It is hoped that the falcons will provide a cost-effective method of significantly reducing bird damage to grapes in the local vineyards.
- Bird damage causes considerable economic damage to the New Zealand wine industry, estimated at $70 million annually.
- The growth potential based on industry size in Marlborough is large being 10,000ha of grapes in a region of 200 square kilometres.
- Successful falcon control, like a resident cat in a warehouse, will be cost-effective. It may also allow vineyards to replace trees which have been taken out because of the small bird threat.
Πηγή δημοσίευσης: Falcons for Grapes Project, Marlborough