BIRD CONTROL ON TENDER FRUIT
Adapted from an article by Hugh W. Fraser, K. Helen Fisher & Ian Frensch, OMFRA

Bird damage to tender fruit is a serious problem for many growers. Some birds that cause problems in fruit crops include: robin, starling, grackle, gull, blackbird, grackle, gull, finch, oriole, cedar waxwing and mockingbird. It is important to know how birds behave in order to control them. Here are some facts about bird behavior: Large flocks of birds are easier to scare than small ones. Birds are opportunists, feeding on whatever is available. It is difficult to break birds of the habit of feeding in a particular area once they are established. Birds establish their home territory in late April and May and often remain in the area until the crop ripens. Crops near roosting or nesting areas, wood lots or ponds are more vulnerable than those in the open. Birds acclimate quickly to uniform movements or noise patterns. Birds can be diverted to other nearby feeding areas. Birds will endure significant hardship to feed. Birds often follow the same flight patterns to feed. Birds usually feed early in the morning around sunrise and late in the afternoon around sunset. Some birds travel in migratory flocks, while others fly in from local woods. Birds feeding on your crop will attract other birds, compounding the problem. The sweeter and earlier the variety, the more attractive it is to the birds. Even if crops are protected with netting, birds may perch on the nets and feed through them or find small holes.

There are four types of bird repellent methods currently available to growers: acoustical repellents, visual repellents, physical exclusion, biochemical repellents. An integrated approach, using a variety of these repellent methods is needed.

Acoustical repellents rely on sound to scare birds away. Birds have a hearing range similar to humans, so if people can hear it, birds can hear it. Unlike rodents, birds cannot hear ultrasonic sounds. The most familiar acoustical bird repellent equipment is the propane-fired cannon that produces loud, unexpected blasts. These vary from mechanical single-shot units, to fully electronic, randomized, rotating multi-shot units. The latter are the most effective over the long term, since the timing and direction of the blast is truly random and the birds do not know when or where the next blast will occur. Although the loudness of the blast is important, it is the unexpected nature of the blast that keeps birds nervous. Birds quickly get accustomed to units that are stationary, shoot at regular intervals, or fire very rapidly. More blasts are not better. Unfortunately, neighbors never get used to propane-fired cannons. Guidelines on the use of propane-fired cannons are: Set at intervals greater than 3 minutes. Use between sunrise and sunset when birds feed. Operate no more than one unit per 5 acres, unless it is absolutely necessary. Ensure that propane tank valves do not leak, as this can cause units to blast unintentionally, even when they are shut off. Move the units around to keep the birds off-guard. Use electronic clock timers that automatically shut off the units.

Electronic sound devices can be less irritating to neighbors than propane cannons. There is distress calls that mimic individual bird species. The Bird Gard uses digital recordings to produce distress calls of specific birds. They are only effective against the bird species whose distress calls are encoded on the microchip. However, some residual repellent effect may be noticed on species that normally travel together with the target birds. Farmers report that digital units also attract birds of prey, such as hawks, who misinterpret the electronic distress calls for the real thing. Hawks circling the farm will also scare away birds. Even though these units produce electronic bird distress calls, they sound to us like real birds, and are usually not as objectionable to neighbors. These devices also produce a lower decibel sound level than older bird alarms and propane cannons.

Whistling and/or pyrotechnic cartridges are launched from a hand-held pistol and produce a loud, whistling sound throughout their flight. There is also a delayed reaction banger cartridge that travels through the air in silence, then explodes high in the air near flocks of birds as they are flying with the same sound level as a propane-fired cannon. Shooting these ear-piercing sounds into a flock of birds works well as a repellent, and can quickly clear a field, wood lot or transmission line before the flock lands on the crop. They may be the most effective manual scaring device available. Shotguns are often used to repel birds, but they are not as effective as launching the sound directly into the flock like the pyrotechnic units. Although shotguns might provide a frustrated grower with a form of stress relief, even an excellent marksman will never seriously reduce the bird population.

Visual repellers are usually used in combination with acoustical systems, and are rarely sufficient by themselves. Birds generally have very good eyesight and react to both movement and things that resemble their enemies.

New visuals devices include hawk effigies like the Jackite that is a life sized hawk kite tethered to a pole. Another is a scare windmill that use reflected ultraviolet light that looks like birds taking of in fright.

Streamers and flash tape are strips of shiny plastic tape which are strung over crops. They move with even the slightest breath of wind and also reflect sunlight. From above, the birds view an entire vineyard or orchard that appears to be in motion. It is especially effective to string streamers and flash tape along perimeter rows where the most severe damage occurs, or in other areas that need additional protection.

Netting is the best way to ensure crop protection. Unfortunately, it is usually the most expensive option, although the cost of netting material has been dropping over the years and the systems for applying the nets are improving. Nets offer almost 100% bird protection and help maximize yields. Draping the net directly over the crop is best suited for crops which do not require multiple pickings, such as grapes. It is labor intensive to both install and remove netting that tangles with the plant. Overhead netting systems are most effective for blueberries, dwarf sweet cherries or high value wine grapes in heavy bird-pressure areas. Nets must be removed or at least retracted at the end of the season to protect them from ultraviolet degradation and snow loads.

With the improvement of digital audio devices like the Bird Gard, many growers are using a combination of audio devices and netting. This reduces the cost of netting and the labor involved.

Many growers hope that there is a single magic solution to their bird control problems. Other than netting, using only one deterrent system often doesn't work. However, using existing bird control methods more effectively may be all that is needed; use an integrated approach, start early with a control program, and avoid predictable control patterns. Consider the following when planning a control strategy: Use visual scaring methods (like the Jackites and scare windmills) in combination with sound (like the Bird Gard with distress calls). Random, unexpected noise is always better than predictable, patterned noise. Position more scaring devices along the perimeter of fields, near trees/ponds, and at flight pattern entry areas. Farms along hill faces benefit from the echoing effect of propane-fired cannons and electronic sound devices. Use prevailing winds to your advantage to maximize sound dispersal. Electronic sound devices and propane-fired cannons should be installed to direct sounds as close to the fruiting zones as possible. Once birds have a taste of your delicious crop, it is difficult to break their habits. Therefore, you must stop the birds from getting an initial foothold on the vineyard or orchard. During the nesting season, some birds can be convinced to settle elsewhere by using electronic bird scarers in the nesting area. Come harvest time, growers often start their bird control program too late, after the birds have already tasted the ripened crop. If you start your program at the first sign of bird damage, there are two benefits. It's easier to scare birds away before they taste the fully ripened fruit and, second, flocks arriving later will often follow the birds repelled earlier. Bird control equipment must be in place at least 10 days before the crop is attractive to the birds.