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Photo: Ben Heide Photography

MANY native and introduced birds in Australia can cause significant damage to grapevine – and do it fast. The NSW Department of Primary Industries says the main problem species are starlings, sparrows, European blackbirds, silvereyes, parrots and lorikeets, cockatoos, honeyeaters and corvids.

There is a diverse range of options for managing pest birds. They have variable effectiveness and no single solution is applicable to all situations.

Most crop damage occurs during the ripening season, which coincides with the busiest time for growers.

As a result, bird management is often not initiated until after considerable damage has already occurred.

Integrated pest management is a concept well understood for insect and disease problems, but birds are rarely managed in the same strategic way.

Rather than focusing simply on killing as many pests as possible, it is now realised that, as with most other aspects of agriculture, bird management needs to be carefully planned and coordinated.

Bird control is just one aspect of an integrated approach to the management of production.

Many birds are highly mobile and can readily replace those that are killed in control programmes.

Unless actions are well planned and coordinated they are unlikely to have a lasting effect.

When planning bird management there are some important steps that should be considered.

What is the problem? In the past, the pest was usually seen as the only problem.

Hence the solution was to kill as many as possible. We now know that the situation is more complex.

First, determine what the problem is. It may be reduced crop yields, secondary losses causing downgrading of fruit, complaints from neighbours, or emotional stress from worrying about the next attack.

Several things impact on each of these problems and controlling birds is often only part of the solution.

The following questions will help define the problem:

  • Where is the problem?
  • How severe is the problem?
  • Will the problem change with time?

IDENTIFY THE BIRDS INVOLVED

Implementing an effective bird control program requires a basic understanding of the ecology and biology of the targeted pest species and (in some cases) those species affected directly (non­targets) or indirectly (prey species) by a control programme.

Control strategies can be targeted at particular groups of birds. For example, some species such as rosellas, sparrows and European blackbirds are largely sedentary and may live in and around a crop throughout the year.

Trying to prevent them from entering and damaging the crop only during the time it is vulnerable is very difficult without applying some out-of-season management of these species.

This is in contrast to the control strategies appropriate for species such as silvereyes and many honeyeaters that are highly migratory and only move into crops during specific periods.

Their control needs to be initiated only if any of these periods coincide with the time that the crop is vulnerable to damage.

Native birds need to be identified because most of these species are protected and permits are required for their control.

Furthermore, most native birds are beneficial or desirable, so it is important that management does not affect these species.

Conversely, some birds can be both beneficial and pests. Honeyeaters for example, can become a more serious problem in orchards during seasons of poor Eucalyptus flowering, but also consume many damaging insects throughout the year.

Other information sheets are available on individual pest bird identification, biology, movements, habitat, feeding behaviour and the damage they cause.

ESTIMATE THE DAMAGE CAUSED TO PRODUCTION

Estimating the amount of damage and calculating the cost will provide a basis for deciding how to best reduce pest bird impact and how much the grower can afford to invest in any control effort.

The percentage of crop damaged by birds in an orchard block can be estimated by randomly or systematically sampling rows, plants, and individual fruit or bunches.

Bird damage to individual fruit or bunches can be estimated by counting, weighing or by using a visual estimate.

Often sampling and calculating damage for the edges of a crop separately will increase the efficiency.

IDENTIFY ANY KEY CONSTRAINTS

Consider legal, social and environmental issues. For example, will scaring devices be acceptable to the local community, and are the techniques legally and/or environmentally responsible and acceptable?

And decide when the most cost-effective time it is to implement the plan.

Even when good information is available it is often not practicable to be immediately responsive to short-term fluctuations in bird numbers or the damage they cause.

When dam­age becomes significant it is usually too late to implement control. For example, effective use of scaring often requires a ‘start early’ approach to prevent birds establishing a feeding pattern.

Likewise, investment in netting cannot be simply withdrawn for those seasons in which damage is below the cost–benefit threshold.

Instead, we may need to look at costs and benefits over a longer time frame and make decisions accordingly.

If damage in the area is likely to be high or there is a history of high levels of damage, the grower should be more inclined to invest in continuing management action.

Measuring damage this year will help in selecting the optimal management option next year and beyond.

DEVELOP THE MOST APPROPRIATE BIRD MANAGEMENT PLAN

Importantly, the management plan must have details of what will be done, who will do it, when it will be done and how much it will cost.

Options can include individual techniques or combinations, and different levels of application.

The plan must have long term, year-to-year strategies to prevent damage and short-term reactive strategies to cope with sudden increases in damage.

For example, in the long term, managers may use netting on a small part of their crop every year.

In the short term, when damage is higher, they may also implement a scaring programme.

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