Bird damage in vineyards and orchards can reduce yield severely, even causing total crop loss. Keeping them out of vines or trees is not easy, and most growers find that a variety of methods have to be used - they get used to any single scare device and the systems need to be rotated to keep birds on the move.
Birds easily become habituated to a particular sound or visual cue.
Often flock birds send out particular individuals or ‘scouts’, which will locate ripening fruit and attract the rest of the flock. Once they have learnt about a food source, they can be very determined and difficult to move along. Bird behaviour is continually modified by food conditions and weather, for instance heavy rains in the Mount Lofty Ranges this season flushed a lot of nectar out of eucalyptus flowers, encouraging birds to move into vines in large numbers looking for sugar from the grapes.
Proximity to native vegetation is a strong factor in fruit losses. As you go out into the middle of the vineyard, the damage is reduced. Many of the techniques reviewed in this article can therefore be employed around the edges of a paddock or planting block. Birds in the centre of a large area of vine are more susceptible to natural predators and are generally more wary, and feed for a shorter time in each spot.
Pest pressure is usually greater in the morning, reducing through the day until it gets more intense again before dusk. It is useful to observe bird flight paths too, as they often prefer to enter a feeding area from a particular direction. Birds that have been hunted will be more irregular in their patterns.
Shooting is an effective deterrent for most birds. A licence or permit is required to take native birds, and they can be very hard to actually hit, due to size (eg blackbirds) or cunning (crows). Only and occasional kill is required for the birds to associate the bang with death. Shooting is difficult in closely built up areas, is expensive and time consuming. In a previous Acres there was a brief article on Frank Wolper’s device - an old fuel funnel strapped to the end of a 22 rifle with bird shot. This produces a loud retort aimed in the direction of the birds and is much cheaper than a shotgun to use.
Most other noise devices are much more effective if backed up by occasional use of a gun.
It is important to recognise that killing birds, especially native avifauna, is an emotive issue. Actual shooting should always be humane and habits such as hanging dead birds from trees as fences should be reserved for areas away from public roads.
Various forms of hawk kites are used to scare birds away. Two basic forms are the ones which are set permanently on tight wires and the kite on a tether which can flap wildly in the wind. Both devices generally have some loose ‘feathers’ which can flap.
Scare kites suit the topography of steep valleys and hills, where tight wires are easily stretched. They require more engineering support on flat land, which makes them more expensive. They always benefit from being moved too, otherwise they only scare passing birds and local populations soon realise they are fake.
Owls and snakes:
A plastic owl is used by many ‘boaties’ to keep birds out of the rigging of moored boats. While birds will get used to them too, the natural habit of owls to sit still and watch is appreciated by the birds, and they will stay away for a while.
Some people swear by a plastic snake in a tree, but this system is not ‘visual’ enough. In other words the bird has to be in the tree or vine before they see the snake.
Flashing lights and flapping ribbons:
Lights and flapping ribbons or balloons on a string disturb birds too and keep them on the move, however some devices need frequent attention and birds do get habituated. A cheap alternative is plastic bags which invariably flap loose. They require effort and if neglected become ugly litter.
One of the better flashing devices is the Betta Bird Scare, sold by Lobethal orchardist Roger Brockhoff. It is a thin pressed metal device with an aerofoil design, so that it moves with very little wind. It hangs on a wire with a strong graphite metal toggle, so that it rotates easily with little air movement. The shiny surface produces a surprisingly high level of flashing, because of raised circular bumps. Roger and his family own and operate an apple and mixed fruit orchard which backs onto the Stirling Conservation Park and the property is divided into smaller areas by windbreak trees, but this is the only scare device he uses. Roger estimates bird losses at 5% for most of the orchard, and double that near the Conservation Park, although individual trees will suffer higher losses. The devices can be reused and should be removed from the field when not needed to avoid habituation and keep the surfaces shiny. A suspension wire above the vine is recommended, although scares hung in the vine or in trees are also effective.
Many people make a local version of the “beer can windmill”. Made cheaply from two aluminium drink cans with tin snips, it spins on a length of wire causing a rattling noise and reflecting light. A better excuse for drinking beer could not be found on many small fruit blocks.
Scare crows are again becoming popular, often with the involvement of local schools. several people spoken to during the preparation of this article had donated material to a school which produced the scarecrows.
They work much better if they can be relocated, if you keep up an actual human presence in the area and if there are enough to cover the main perimeter from which attack is likely. Streamers, ribbons and scarves which flap may help too.
Scare crows work very well in tourist areas such as the Barossa Valley, where they contribute to the aesthetics of the region, rather from detracting from it with noise or actual destruction of birds.
Scare guns are a very controversial issue in peri-urban areas. The Mount Barker District Council recently took a decision to not permit noise generating scare devices on new developments within the district and they are debating whether to ban all noise devices from the council area.
David Paschke is a grape grower from Woodside who recently bought a new gas gun with a sliding barrel. He says “if you push the barrel in the volume is reduced by two thirds”. It is a single shot gun, which is less annoying than double or triple bangs. The gun cost just under $500. The guns often get ‘leaky’ when they are old and poorly maintained, leading to very loud retorts. David offers this advice on using scare guns, “even though the volume is less than older guns, some areas will echo. They should be pointed away from houses and be located where there is no echo or no-one to be bothered by echoes, and where the wind blows onto the crop, but not onto houses”.
“If you don’t shoot, the birds get acclimatised to scare guns, rise up after every bang and just drop back into the crop.”
Adrian Strachan is a grape grower from Willunga who uses a scare gun on a trailer which he pulls behind a Trike. “The Trike has to start every time, then you don’t mind moving the gun. The gun is placed according to where the birds are and wind direction.
Other noise devices:
A variety of other noise devices are available. They include alarm or distress calls (“Squawkers”)and piercing sounds (“Screechers”) which interrupt flock communication or cause discomfort.
Different birds species react to different sounds or combinations of sounds. Some such as silver eyes are slow to respond to most sounds. Suppliers such as Bird Blaster or Bird Gard offer a range of products which can be ‘tuned’ to particular species. They include random mixed sounds, which are described as “harassment sound,: not distress calls.
All sound devices still need management, such as attention to speaker direction and height and the time intervals for which they are used.
Netting made from high density polyethylene or similar materials is becoming much more popular, especially in areas where returns from vines are high. When it works well it provides virtual total exclusion, permitting vines to be planted even close up to scrub and windbreaks.
Cost varies with volume - around 40c square metre or $2.00 per linear metre for a net five metres wide. Whereas early nets covered individual rows, it is now possible to cover six rows at one time. Biodynamic grower Ben Pridham owns and operates a spreading machine. He says it is possible to cover 20 km of row or 2.2 hectares per day with 15 metre wide net, which covers 4 rows. Long rows on flat land can be covered faster. Different vineyards offer different opportunities for hang ups on posts or foliage wires.
A 100 m roll of 15 m wide net costs about $525. To put it on costs $150 per day for the machine, $35 per hour for the tractor and three people for the labour. He recommends that each row is stored in a separate bag and marked accordingly, so that it goes out on the same row each year. This is especially useful where there are different row lengths. He also recommends zip ties for fastening. Surprisingly Ben says retrieval is faster that putting the nets out. He said “The netting must be white, as it is a much better visual deterrent for the birds and they will tangle in it less. They can’t see black net.
Ben also has an area of fully enclosed orchard, costing about t$100,000 for ten acres. When I asked if such an investment was worthwhile he nodded towards a patch of apples devoid of fruit - “they got every one of those” he said, “I just wouldn’t have a crop”.
Nets must be designed for the high ultraviolet conditions in the Australian sun. High density polyethylene yarn may last for ten years if treated well.
Additional benefits often result form netting. Bird and hail protection are direct results, but nets also induce microclimate variations, including airflow reduction and temperature modification. Secondary effects from wind protection include reduced spray drift, reduced evaporative losses and protection from light frost.
Trevor Desmond, from SA Netting believes that “the piece of mind which nets permit is worth a great deal to many people, especially those who do not live or work on the land. Many people report how much more relaxed they are in the lead up to harvest.”
He continued “with a movement from 11.5 to 14.2 boume for Chardonnay, it is possible to get 21% on top of the base price. That means you have to let fruit sit on the vine”.
“We also find there is less water usage from the shade effect which can be useful in a late hot spell.”
According to Trevor, nets “can be placed by hand, with a team of five people covering five acres of vineyard in five hours”. Some nets come with the centre line marked, which greatly assists locating the net.
A variety of repellents have been trialed and a few are marketed, including D-ter, which contains ammonium aluminium sulphate. It may be applied as a spray or a dust. Anything bigger than a light shower requires reapplication. It has the advantage of being humane and suitable for use close to dwellings and most users report that it is effective.
Encouraging competetive species
Many insectivourous species whichare useful pest controllers may also compete with pest birds for space. They behave territorially, and defend ‘there patch’. This strategy is used by Brian Mason, and apple grower from Forest Range in the Mount Lofty Ranges. He has won many awards for nature conservation on the property, which contains several dams and a large area of bushland. Although the competing species may take an occassional fruit, they do help to protect the crop from large flocks of visiting pest birds.
The late Alfred Haupt had a great idea for encouraging raptors (birds of prey) into his oilseed crop, to disuade pest birds from hanging around. He noted that they liked a high perch, and that most of the trees were gone from the paddocks. To rectify the lack of places to sit and scan to territory, he installed ten metre high posts, with a cross piece. Mark I of this design had a metal crosspiece, which got too hot in summer. Mark II had a wooden cross piece and worked much better.
Parts of the Mount Lofty Ranges close to Adelaide are experiencing rapid urbanisation and conversion of smaller properties to ‘lifestyle’ farms, in the proximity of established orchards. Many of the orchards have relied heavily on scare guns for bird control. There is also a rapid expansion of viticulture, with resulting environmental issues such as chemical overspray (onto vines from adjoining properties and from vineyards into surrounding land uses), water consumption and water rights, and scare guns.
The District Council of Mount Barker has responded to complaints from the community by banning audible scare devices from new developments. In the Adelaide Hills Council district, arguments over audible devices, including gas guns and screechers, are getting louder.
David Paschke (see above) is also an elected member of the Adelaide Hills Council. He says “it is a really emotive issue, but I believe we can manage scare guns. They should not be used up close to houses where people might object, but it is possible it most areas to use them away from neighbours”.
“We monitor the number of birds every day and we don’t turn the guns on unless they are needed. We don’t run them from daylight to dark, but we vary the use. We also do some actual shooting, which is really necessary to support the scare guns.”
“We also drive through the vineyard on the motorbike and we use kites and scare crows, and an Airport Screecher, with a wounded bird call, beer can devices and shotguns.’
“We have not used netting, at $5,000 a hectare, and with problems of putting it on and off, storage, and it may only last 5 to 8 years with maximum care. We will purchase some netting now for a corner near the scrub block, but we have seen where birds will still get under netting, and we see them walking along the top pecking fruit through the net.”
“We have to keep moving the beer can devices and the kite, which does get damaged by the wind and needs to be repaired several times per season.”
“Wattle birds are the worst for us, followed by starlings, crows and the bigger birds. Magpies take exposed bunches and wood pigeons cause havoc near the scrub block.”
“Best of all is to be in the vineyard and to shoot a few birds. It is also a fact that the more gas guns are taken out of use the more birds will be shot.”
“I can’t see the sense in banning scare guns every where when there may be areas where all the neighbouring properties want to use them - there must be some sensible zones. I’m the first to admit that 100 metres is too close to a dwelling. We should take into account wind and move the guns so as to not intrude.”
“It is a problem that land agents don’t make newcomers aware of planning uses such as this one before they buy the properties.”
David also said “horses need to get used to them gradually too, by slowly moving them closer, and they should not be used close to roads where kids ride.”
Mount Barker Councillor Paul Stephenson who moved the motion banning audible scare devices is much less impressed with the guns or screechers. He said “they are an unreasonable intrusion and no one should have to put up with them”.