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9. Parrot Problems (from a human viewpoint)
- Johns Hopkins University Press
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159 Are some parrots agricultural pests? I pulled up next to the fruit packing shed and went in search of the landholder. I had been asked to assess the damage done to his apple crop by Gang-gang Cockatoos (Callocephalon fimbriatum), a threatened parrot endemic to southeastern Australia. Following a brief discussion about the weather, the farmer took me to look at the block where the birds had been feeding. A few rows along the farm boundary had been badly impacted, the ground littered with bits of apple removed by the birds in their quest for seeds. Talking to the landholder, it became apparent he had made no effort to harass the birds when they began visiting his orchard. The initial damage was slight and he was generally sympathetic to wildlife. Once the level of damage had become a concern, ad hoc efforts to scare the birds off the crop had failed. I hung around to await the arrival of the cockatoos late in the afternoon. Right on time, 15 birds flew into a stand of remnant vegetation bordering the orchard. They paused briefly before dropping down into the apples to feed. Without allowing them time to settle, I chased them out of the orchard . The startled birds sheltered in nearby eucalypts, but soon returned to the crop. This time, I allowed them to feed for 30 minutes before attempting to scare them. Moving the birds out of the orchard proved much more difficult on this second attempt. They were more inclined to shift to a different part of the orchard and continue feeding than retreat to the safety of the remnant vegetation. The message from this simple experiment seemed clear. Allowing birds to settle on the crop and feed for any length Chapter 9 Parrot Problems (from a human viewpoint) 160 Parrots: The Animal Answer Guide of time reduced the effectiveness of harassment techniques and could result in increased crop damage. I wandered back up to the farmhouse and sought out the landholder. We sat down and discussed the various options for minimizing crop damage. I explained that now the cockatoos had developed the habit of feeding in his orchard it would be difficult to alter their behavior. Commonly employed scaring techniques (e.g., explosive cartridges, gas guns, and harassment by vehicle) would likely work, but needed to be part of a well-thoughtout pest management strategy. He needed to be committed to maintaining the scaring program until the threat posed by the cockatoos no longer existed. Netting was an option and had the advantage of being effective in the absence of people. Many of the surrounding orchards had been netted to prevent hail damage, which had the additional advantage of reducing the impact of bird pests. Ultimately, the methods to be employed would depend on the cost of control versus the cost of lost production. In this situation, the level of damage caused by the cockatoos appeared insufficient to warrant control. Within Australia, a wide variety of crops are affected by parrots. The cost of parrot damage varies between farms and years. The impact at a regional level is typically small. Parrots are a serious pest of horticultural crops, consuming buds, flowers, and fruit. In South Australia, Crimson Rosellas (Platycercus elegans) foraging in cherry orchards can remove 10–90% of the buds from trees within a block. Cockatoos are a significant pest of grain and oilseed crops, birds feeding on germinating seed, standing crops, and stubbles. The propensity of cockatoos to form large flocks means they are preadapted to the exploitation of abundant, ephemeral food resources. Different crop stages may be exploited by different cockatoo species, while some crops are favored over others (e.g., oilseeds are preferred to grains). In addition to their direct impact on yields, parrots can damage agricultural infrastructure. Cockatoos attracted to peanut farms in northern Queensland make use of their powerful bill to chew through the electrical wiring of pivot irrigators. This results in irregular irrigation and subsequent yield reductions. In addition, there is a cost associated with the repair or modification of equipment to make it less vulnerable to cockatoo damage (e.g., steel casings for wiring). In the Neotropics, parrots have long been considered agricultural pests. Enrique Bucher noted that pre-European cultures in South America had problems with parrots attacking corn plantations. Charles Darwin commented on the status of Monk Parakeets (Myiopsitta monachus) as agricultural pests: “These parrots always live in flocks, and commit great ravages on the corn-fields...