WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Birds

Vertebrates

 

Symptoms

Damage to blueberries by birds can be a serious and perennial problem, and may result in yield losses of 10% or higher. Birds are most problematic nearing and during harvest, as the fruit are turning blue and the sugar content in the fruit is increasing.

Damage to fruit can be caused in several ways; fruit may be knocked off of bushes during foraging, eaten wholly by the bird, or punctured or pecked at by a bird. Punctured fruit often go unnoticed and are more susceptible to fruit rots, which may cause spoilage and rejection of packs of fruit.

Different bird species will cause different types of damage to fruit. Larger birds will eat whole fruit and smaller birds will peck at fruit to cause puncture damage. Robins and starlings are the most common pests but other birds are also known to cause damage.


Identification

European Starling (Sturnus vulgaris)

Starlings

Introduced in the early 1890’s, the European Starling has become a pest bird in many areas of North America. They appear black, but will shimmer green and purple, and are about 8-9 inches long with a wingspan of 12-16 inches. They will take over nests of other bird species. The calls of this bird are loud with a wide variety of sounds, often imitating calls of other birds. Starlings will invade blueberry plantings in large numbers and feed on fruit by eating them whole and will puncture the fruit with their claws. These birds thrive in areas with dairy and blueberry operations nearby which offer them year round food. These areas are commonplace in Northwestern Washington State making starlings a problem bird.

Starling

http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/European_Starling.html#sound
http://www.birds.cornell.edu/birdhouse/bios/sp_accts/eust
http://identify.whatbird.com/obj/160/overview/European_Starling.aspx
http://birdweb.org/birdweb/bird_details.aspx?id=360

American Robin (Turdus migratorius)
Robins are about 10-11 inches long with a wingspan of 12-16 inches. They have grey backs and wings, a reddish-brown chest, and a yellow beak. Their song is musical and sounds like "cheerily, cheer up, cheer up, cheerily, cheer up."

Robins feed mostly on insects and earthworms, but will also eat blueberries whole. When they are foraging for blueberries, they may knock other ripe fruit off of the plant.

http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/American_Robin.html
http://identify.whatbird.com/obj/212/_/American_Robin.aspx
http://birdweb.org/birdweb/bird_details.aspx?id=354

House Finch (Carpodacus mexicanus)
House finches are about 5-6 inches long with a wingspan of 8-10 inches. Males are bright red on the face and neck with brown on the rest of the body. Females are brown and striped. Their song is a warble that goes up and down in pitch.

Finches will feed on blueberries by pecking the berries. This will cause damage to many berries on the plant, but will not remove fruit.

http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/House_Finch.html
http://birdweb.org/birdweb/bird_details.aspx?value=search&id=456
http://identify.whatbird.com/obj/105/_/House_Finch.aspx

Red-Winged Blackbird (Agelaius phoeniceus)
These birds are 7-9 inches long with a wingspan of 12-16 inches. The males are most familiar with a black body and showy bright red shoulders that are fully exposed in flight. The females appear as larger house sparrows with dark and light striped plumage. Their song is a gurgling noise.

Red-winged blackbirds will feed on berries when in season, but feed mainly on seeds.

http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Red-winged_Blackbird.html
http://identify.whatbird.com/obj/144/_/Red-winged_Blackbird.aspx
http://birdweb.org/birdweb/bird_details.aspx?id=438

 

Monitoring and Decision Making

The decision making process for bird control depends on two areas of information: understanding the type, number, and timing of birds as well as understanding the severity of damage to the crop and what type of monetary loss this represents.

Scouting for birds can be done during regular scouting periods, but the best time of day to look for birds is in the early morning or just before dusk in the evening. A minimum of one location per 20 acres should be monitored daily, with the location in the area of bird travel. Binoculars should be used to identify bird species. Knowing the type of bird that is a problem in a field may determine the appropriate method of control. Keeping records of bird populations before and after a treatment, and for subsequent years, can help to determine the efficacy of control treatments. By identifying where damage occurs most often, control treatments can be concentrated in affected areas.

Decisions on the type and expenditure of bird management techniques can be made by evaluating the amount of damage there would be to the crop and the potential effectiveness of certain treatments. This can be done by using a cost-benefit analysis considering one or several combined treatments, following suggestions from a study in New Zealand (Spurr and Coleman, 2005 and modified by Cathy Heidenreich, Cornell University).

To determine the cost effectiveness of the treatment, we need to know the loss to birds that are regularly experienced and the efficacy of the proposed treatment (reduction in loss to birds). Assuming a berry crop yields $10,000 per acre, the table below can be used to determine the maximum cost per acre that can be spent on bird control.

If we take, for example, a berry crop worth $10,000 gross per acre with the regularly experienced loss to birds of 10% and the treatment under consideration is thought to be 25% effective. This treatment should cost less than $250 per acre to be cost effective. In the case of treatment equipment that lasts for several years, such as netting, this value needs to be factored in as well.

Once threshold levels and cost levels for treatment have been established, a management plan can be developed. This plan should take an integrated approach with management techniques encompassing several stages of fruit growth.

Monitoring should begin when the fruit is green. Controls should be implemented soon after, before flocks become established in the field. Post-control monitoring should be done to evaluate the success of the treatment. The performance indicator will be measurable and directly related to the problem, for example, the amount of fruit damage. A performance indicator not related to the problem, such as the number of birds trapped, will not reveal the efficacy of the treatment.

 

Thresholds and Management

Detection of birds in a field area is the threshold for initial treatment.  A bird treatment plan needs to be developed based on field size, number of birds, and type of birds present.

Several bird management techniques are available but few, if any, work well when used on their own. Combining tactics of visual and auditory deterrents, cultural practices, exclusion, and increasing predator habitat have been found to be most effective.

Birds will habituate to most auditory and visual control methods that remain in one place. To be most effective, these controls must be moved around the field on a regular basis. Using a variety of scaring devices together may be most effective in reducing bird damage.

Control methods should be in place before fruit begins to ripen in order to scare birds off before they establish in a field. Auditory or visual deterrents placed in a field when fruit is ripe may become a signal to returning birds that food is available.

 

Cultural Management

Site location can have a large impact on the amount of bird damage to a blueberry field. Isolated plantings and small plantings tend to have higher damage than larger plantings and those in close proximity to other fields; the damage is usually spread out over a larger area so a lower portion of the fruit is damaged. Seed eating birds will be attracted to areas where weeds and grasses are allowed to go to seed; mowing grasses around the field may help to control these birds.

 

Exclusion

Exclusion can be a very effective method for controlling bird damage and is generally most practical in smaller fields. The materials (posts, wire, netting, etc) and installation costs for bird netting is prohibitively high for some growers and can be impractical for the movement of machinery, such as harvesters, in the field.

Netting covering crop

Netting can be placed directly over the plants or a framework structure of 6-10 feet tall can be constructed over the planting to support the netting. The netting should have ¾” mesh to ensure that all birds are excluded. Initial costs of this system are quite high, but the materials will last over several seasons and the costs should be pro-rated over this period of time.

 

Visual Deterrents

Visual Deterrents generally fall into two categories: those that simulate predators and those that are shiny and reflect light. Predator simulators include large hawk-shaped kites, large inflatable balls with reflective predator eyes and markings, and animated owl figures. They range in price and are available in various sizes and colors. These devices are generally more effective if paired with an auditory deterrent such as a distress call or a predator attack call.

Jackites are hawk or predatory bird shaped kites that flap in the wind when strung up above a field. These should be attached with monofilament line to a 20 foot long bamboo pole. About one or two are needed per acre (depending on field size and bird pressure) and should be placed mainly around the perimeter of the field. Jackites should be moved every 2 days to avoid pest birds from becoming habituated.

Helikites are mylar balloons that should be filled with helium and flown in a field attached to a bamboo pole with monofilament line. They will fly to 100 feet above ground and will move around the field with the wind. Helikites should be brought down overnight (the dew weighs the balloon down and can fall into brush and tangle the line) and in high wind conditions.

Reflective tape is attached to the wires and moves with the wind. This may deter some birds but has not been found to be very effective in reducing damage.

 

Auditory Deterrents

Auditory deterrents are either as explosive sounds, such as cannons, or bird calls.

Bird auditory deterrents can be an effective tool in preventing bird damage to blueberry crops. However, if they are used thoughtlessly, they can seriously disturb neighbors which may initiate legal controls or ban of use. Groups in Whatcom County, British Columbia, and other areas around the world are dealing with neighbor relations around the use of bird scaring devices. A document has been developed for blueberry farmers in Whatcom County that describes guidelines to using the bird scaring devices in a way that can foster good relationships between farmers and neighbors.

Good Management Practices - Interim Guidelines for the Use of Propane Air Cannons and Other Bird Scare Auditory Devices

Propane Cannon

Frightening devices, such as cannons, sirens, and bangers, are commonly used in Oregon and Washington blueberry fields but offer only short-term control. If the source of the sound remains in the same location, most birds will become familiarized to and ignore the sound. The birds may fly off when the sound is made, but will often return to feeding. Explosive sounds may be more effective when moved around the field, combined with a realistic scarecrow holding a gun-like stick. This method may be compounded by a person driving through the field shooting a starter-pistol to make the shooting sounds more realistic and threatening.

Broadcasts of recorded distress or alarm calls have been used with some success but, as with the explosive noise devices, the birds soon become comfortable with the sound. In addition, the distress or alarm calls are often species-specific, and their success is dependent on the grower being able to identify the species causing the damage; broadcast sounds must at least be calls of bird species that are present in the area. Birds have dialects that are specific to a certain area; using calls from the local bird dialect will be most effective.

Speakers

The quality of the distress call sounds may be a factor of success; the intricacies of bird calls, including distress calls, must be replicated to a level where they will trick and scare a pest bird in order to be worthwhile. Distress calls may be more effective when paired with a moving hawk or owl figure clutching a moving prey, such as a bird to represent what a prey bird would normally experience visually with the auditory cue.

Using the calls of predator birds may not be as effective. These birds rarely make calls when attacking, as this would warn the prey bird that they are nearby.

 

Predatory birds

The use of predatory birds, such as the American Kestrel (Falco sparverius), has been effective in controlling starling populations for some growers. These birds are highly territorial and eat birds, rodents, and large insects. Their presence is a deterrent to problem birds such as starlings.

Kestrel

Nesting boxes can be used to attract these birds; if a population of kestrels is present, they may adopt these boxes as their own nests. Several nesting boxes should be available so that kestrels can choose the one that is best. Boxes should be placed on freestanding poles or trees 10 to 30 feet above ground and as far away from human activity as possible. The nesting boxes should be monitored to ensure that starlings do not use them for their own nests. Neighbor awareness of this program will help with kestrel nesting; neighbors can erect their own nest boxes to aid in the program.

In order to help to attract and maintain kestrel populations, food should be available. The boxes should be placed in an area near an open field where rodents are present, or in a field with minimal pesticide use to encourage populations of large insects.

Kestrel boxes can be used as nests for starlings. They should be inspected on a regular basis to ensure that starlings or other pest birds are not using the boxes and unwanted nests should be cleaned out.

Kestrel Box

The use of nesting boxes to attract kestrels for problem bird control has been successful in cherry orchards, and preliminary results in blueberry fields show promise.

 

Chemical Repellents

Chemical repellents are sprayed onto the plant and the taste is unpalatable to birds. Methyl anthranilate, an isolate of Concord grapes, is the active ingredient and is considered safe for human consumption by the FDA. This compound is registered for use in blueberries but it has not provided satisfactory results for several reasons. It is a volatile compound with a short residual; it is effective for only a few days. Birds need to consume a large amount of the product in order for it to be effective. The method of application, blast spraying, generally applies only small amounts covering the whole plant; thus, the bird needs to consume copious fruit in order to be effective.

Sucrose solutions applied to plants when fruit start to ripen have been found to be somewhat effective. Birds, such as starlings, may not be able to digest sucrose and will develop an aversion to fruit with a sucrose coating. High levels of sucrose coating the fruit are required for efficacy, which may be difficult to apply in most field circumstances.

 

Pest Bird Trapping

Trapping birds prior to crop ripening can be arranged with government agencies. Most bird species are protected by federal law; protected birds caught in traps must be released unharmed. Generally birds that are trapped are first year birds that are not savvy to the trap structure; many of these birds will not survive to the next year due to other circumstances, so reducing number of these birds may not be effective in control of the population. Older birds will usually avoid the traps, making the success of the traps low.

Farm Friends manages the starling trapping program in Whatcom County. Contact Henry Bierlink at 354-8767 to purchase a trap for your area. Traps will be placed in the area of the farmer who has purchased the trap, but may not be placed directly in the field; the location of the trap is determined by the best potential for bird capture. Traps can be placed from April to October.

The removal of birds by trapping has questionable effect on the pest bird population.

bird trap

 

References

Cornell University, New York Berry News, Vol. 06 No. 6, pages 9-16 “Bye Bye Birdie – Bird Management Strategies for Small Fruit”
http://www.nysaes.cornell.edu/pp/extension/tfabp/newslett/nybn66a.pdf

South Australia EPA: Audible bird scaring devices – Environmental noise guidelines
http://www.epa.sa.gov.au/pdfs/guide_bird.pdf

Australian Government: Bureau of Rural Sciences, Managing Bird Damage to Fruit and Other Horticultural Crops
http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0005/193739/managing_bird_damage-full-version.pdf

Cornell University: The Blueberry Bird Problem – Options for Control
http://www.fruit.cornell.edu/Berries/bbpdf/bbbirds.pdf

Washington Department of Fish and Wildlife, Living with Wildlife: Starlings
http://wdfw.wa.gov/wlm/living/starlings.pdf

 

 

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • 360-676-6736 • whatcom@wsu.edu