SRAC Publication No. 401

SouthernRegionalAquacultureCenter

November, 1990

Avian Predators

Frightening Techniques for Reducing BirdDamage at Aquaculture Facilities

Gary Littauer*

Bird predation at aquaculture facilitiescan often be reduced by use of avariety of frightening techniques.These techniques rely on noise and/orvisual stimuli to convince birdpredators that an area is unsafe.Repeated harassment with frighteningtechniques can sometimes conditionlocal populations of birds to avoidareas where they are unwelcome.

Success in using frightening techni-ques can vary depending on a numberof factors. These include bird species,the mix of techniques used, frequencyand duration of use, availability ofother food sources, location of pondsin relation to roosting and loafingareas, and whether the birds have es-tablished regular feeding patterns. Tobe effective, producers must committo using a variety of techniques andchanging them often.

Audio frighteningtechniques

Pyrotechnics – These include severalfireworks devices used for scaringwildlife. Bird bangers (Bird Bombs®),screamer sirens (racket bombs), and

* Animal Damage Control, Uvalde, TX

whistle cartridges are 15mmcartridges that are fired from handheld.22 caliber blank pistols (Figure 1).All are fired into the air toward thebirds to be frightened. Bird bangerstravel 10 to 30 yards and explode inforce similar to an M-80 firecracker.Screamer sirens travel about 100yards emitting aloud screechingnoise. Whistle cartridges travel about100 yards emitting a whistling noise.It is best to use several kinds of thesedevices so that birds do not acclimateto anyone noise.

Figure 1. Flare pistols are effective whenused in conjunction with other scaredevices.

Shellcrackers produce a noise similarto bird bangers but are fired from a 12gauge shotgun and travel 50 to 100yards before exploding. They havegreater range than bird bangers andare easier to use, particularly from avehicle, since they do not require theseparate step of loading a .22 blank topropel the device. However, they aremore expensive and a 12 gauge shot-gun is required. Short barreled singleshot shotguns with open cylinderchokes are recommended for usingshellcrackers. Barrels should be check-ed before each shot to assure the wadfrom the previous round did not lodgein the barrel. The powder in somebrands of shellcrackers is especiallycorrosive and incomplete burning ofpowder is common. Shotguns shouldbe cleaned after each session of firing.

The rope firecracker is a noise devicethat uses 3/8- or 5/16-inch cotton fuserope and large waterproof firecrack-ers. The fuses are inserted into therope at intervals. The rope is lit atoneend and hung from a stake or other ob-ject. The rope burns (smolders) at therate of about 1 inch per 10 minutesdepending on the weather and igniteseach firecracker which then falls tothe ground and explodes. These canbe hung at strategic locations around

the farm and do not require a constanthuman presence to function. To mag-nify the sound and reduce fire hazard,they can be hung inside a suspendedsection of stovepipe with a wire bas-ket on the bottom.

There is some fire hazard in usingpyrotechnics. Care should be taken toassure they do not come into contactwith explosive or flammable materialswhen being used. Also, eye and earprotection is strongly recommended.Local laws and ordinances mayrestrict use of pyrotechnic devices,and local authorities should be con-sulted before using them.

Automatic Exploders – Thesedevices utilize propane gas oracetylene and an automatic timer toemit loud explosions at controllable in-tervals. Some models emit a variablenumber of blasts (one to three) at eachtime interval to reduce the predict-ability of the noises. This is intendedto reduce the chances that birds willlose their fear of the noise. Rotatingmounts are available for some modelsto change the direction of the blasts toenhance effectiveness. Automatictimers are available for some modelsto turn them on and off each day.Using exploders in conjunction withscarecrows and other control techni-ques probably enhances their effec-tiveness. Older automatic exploderssometimes have a tendency to catchon fire. Although the fire is usuallysmall, producers should avoid locat-ing these devices on or near equip-ment.

Birds can become accustomed to thenoise of exploders. The devices

should be moved to new locations atleast every 1 to 3 days and the inter-val of explosions varied to increasethe time it takes for birds to lose theirfear of the sound. When large num-bers of birds are ignoring exploders, itmay be a good idea to turn them offand resort to more aggressive techni-ques such as patrolling ponds withpyrotechnics and/or live ammunition.Continued use in those situationsprobably just reinforces the birds’tolerance of loud noises.

Recorded Distress Calls/ElectronicNoises – Many species of birds com-

municate fear or distress by alarm ordistress calls. Broadcasted recordingsof these calls can frighten somespecies and cause them to avoid areas(Figure 2). Distress call tapes areavailable for great blue herons, snowyegrets, gulls and double-crested cor-morants. The response of fish-eatingbirds to these noises has been vari-able, and success probably depends onthe situation in which they are used.

haps out of curiosity or an instinctivedesire to mob the “predator” that has“caught” one of their members. Al- though this may seem to be an indica-tion that distress calls cause theopposite effect of that desired, it maybe a good time to reinforce the birds’fear by shooting pyrotechnics at thebirds.

Electronic noise generators (capableof emitting noises of variable frequen-cy and modulation), loud music andtimed siren devices have been triedfor scaring fish-eating birds with vary-ing degrees of success.

Playing distress calls or electronicnoises may not show an obviousdirect effect on bird predators. How-ever, they may reinforce other scaringtechniques. If a local population ofbirds is conditioned to be afraid of dis-tress calls or electronic noises, broad-casting these sounds may mean fewerrounds of pyrotechnics or live am-munition will have to be used, result-

. ing in lower overall costs for birdFigure 2. Control box for broadcasting control.bird distress calls from a pickup.

Live Ammunition – Shotgun and Flocks of certain fish-eating bird rifle fire is effective in scaring birdspecies such as cormorants. gulls and predators from pond complexes.even great blue herons have” oc- Many farmers use live ammunition be-casionally been observed flying cause it is less expensive thantoward broadcast distress calls, per- pyrotechnics.

These various noisemakers have all been used successfully in bird control.

Rifle bullets can ricochet off water soextreme caution must be exercised.Many agricultural facilities will not besuitable for using rifles to scare birdsbecause of safety considerations.Cartridges in .22 caliber rimfire are in-expensive and can be used to frightenbird predators from long distances.High powered center-fire riflecartridges can have a dramatic effecton birds when fired in their direction.This is because bullets fired from ahigh powered rifle often produce aloud cracking noise similar to abullwhip as they pass by. There is agreater risk of inadvertently killing aprotected bird when using a rifle forfrightening purposes than when usinga shotgun. If high powered rifles areused, it is advisable to use smallercaliber, high velocity rounds with oneof the super explosive brands of bul-lets so that bullets have a greaterchance of breaking up withoutricocheting when they impact theground or water. Full-metal jacketedbullets should be avoided since theyare prone to ricocheting.

walking or a vehicle driving on apond levee from long distances (200yards or more). They seem to be moreeffective when used in combinationwith noise producing devices such aspropane exploders. Scarecrows appearless effective against great blueherons. Inexpensive silhouettescarecrows can be jigsawed from 1/2-inch plywood and wired to steel fenceposts. A realistic human shape and fa-cial features enhance its scaringability, and brightly colored paintadds visibility. Hanging the arms sothey sway in the wind adds motion tothe scarecrow (Figure 3).

Vehicles parked on pond levees aresometimes effective scarecrows whenbirds are scaring easily from a vehicledriven by a bird control employee.They should be moved every few daysto reduce the chance of birds becom-ing accustomed to them. Intermittentuse of propane exploders and/orhuman-shaped scarecrows next toparked vehicles may increase theireffectiveness.

Many producers use inexpensivesmall game shotgun rounds fried intothe air to frighten birds. Pyrotechnics,although more expensive, are general-ly more effective because there isgreater variety in the types of noisesthey cause and they get the noisecloser to the birds. However, whenbirds are regularly flushing fromhundreds of yards away, there isprobably less difference in effective-ness between pyrotechnics and liveshotgun ammunition. In general, it is agood idea to intersperse pyrotechnicswith shotgun and rifle fire for maxi-mum effectiveness.

Use of live ammunition can pose arisk of inadvertently killing an oc-casional bird. Producers must havepermits before killing fish-eatingbirds, whether intentional or not (seesection on Supplemental Killing).

Visual frighteningtechniques

Scarecrows – Human-shaped effigiesor scarecrows have shown some effec-tiveness in deterring cormorant flocks.Scarecrows seem to work best whenbirds are easily frightened by a person

Figure 3. Using a scarecrow and propaneexploder is sometimes effective if movedregularly.

Automatic pop-up scarecrows havebeen developed to scare birds. Onemodel uses a mannequin head on asteel rod that is propelled 30 inchesinto the air by a propane exploderadapted for the purpose. Anothermodel uses an inflatable human-

shaped bag, a battery powered electricfan, a siren-like noise maker, and asystem of timers with a photo cellswitch. The timers periodically turnon the fan motor inflating thescarecrow which rises up presenting ahuman shape where none was presentshortly before. The photocell switchcan be set to start the device at dusk ordawn. An initial field trial of thisdevice indicated deterrence of cor-morants from catfish ponds.

Scarecrows should be moved often tonew locations to reduce bird habitua-tion. When birds show little or no fearthey should be removed and aggres-sive scaring techniques should beused.

Radio-Controlled Aircraft – Skilledoperators of radio-controlled airplaneshave frightened cormorants and otherfish-eating birds from aquacultureponds. The birds can be hazed withthe airplanes as they attempt to arriveat pond complexes. Observations sug-gest that one operator and plane maybe required to effectively cover 200 to300 acres of ponds if the ponds areblocked into one contiguous unit.Problems with this technique includeweather limitations, having suitabletaking off and landing places, andrefueling. Even skilled operatorsoccasionally crash radio-controlledplanes. Costs for using this techniquemay be substantially greater thanusing unskilled labor with pyrotech-nics and/or live ammunition.

Other Frightening Techniques –Highly reflective mylar ribbon (flashtape), hawk silhouette kites, andhelium balloons have been shown tobe effective at times in scaring birdsin other damage situations. Their ef-fectiveness in scaring fish-eating birdsfrom aquaculture facilities has notbeen determined, however. Limited at-tempts to use helium balloons on cat-fish ponds identified problems inkeeping the balloons up in winds of aslittle as 5 to 10 mph and in keepingthem inflated sufficiently to remainaloft for more than a day or two.Beach ball type balloons with largeeye spots to mimic the stare of a largebird of prey have been positionedaround cattish ponds with no notice-able effect on fish-eating birds.

Water sprays from rotating sprinklersplaced around ponds or racewayshave been found to repel certain birds,particularly gulls and herons. Ap-parently, the sprays reduce thevisibility of the fish in the water. Theyseem to work best when adequatewater pressure is used combined withan automatic on-off cycle.

Flashing lights have been used with mixed results to frighten night-feedingbirds such as night herons and greatblue herons. Aircraft-type strobelights have an apparent blinding ef-fect, confusing the birds and reducingtheir ability to catch fish. Flashingamber barricade lights and revolvinglights have also been tried with somesuccess. Most birds reportedly be-come rapidly accustomed to lights,however, and other techniques mustbe employed.

Supplemental killing

When birds become accustomed tofrightening techniques, it is often ad-visable to kill a limited number ofbirds to reinforce the others’ fear. Cer-tain legal restrictions apply. ConsultSRAC Publication No. 404 for infor-mation on the legality of killing fish-eating birds and obtaining necessarypermits. In general, it is wise to obtainnecessary permits and to conductlimited, supplemental killing as soonas possible after the effectiveness offrightening techniques has

diminished. Be sure you have bothfederal and state permits if requiredin your state before killing anyprotected species. When using liveammunition to frighten birds,producers must be careful to avoidkilling any birds unless depredationpermits have been obtained.

Control strategies usingfrightening techniques

In most situations, larger flocks offish-eating birds will be easier to scarefrom aquaculture ponds than smallscattered numbers. Producers shouldexpect a reduction, but not necessari-ly total elimination of bird use oftheir ponds from the use of frighten-ing techniques. Key points to remem-ber when using these techniques forbird control are:● Begin frightening programs

before the birds have establishedregular feeding patterns. Thelonger they are accustomed tocoming to a facility, the more dif-ficult they will be to frightenaway.

● Try to frighten the birds beforethey land at the facility. If youcan scare them off early in themorning, you can usually movethem to other feeding areas.

● Use a variety of techniques; donot depend on just one or twodevices or techniques.

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Frequently change locations ofpassive frightening devices such as scarecrows and exploders, andchange the combination of techni-ques being used as often as neces-sary.Be aggressive.

Pursue limited kill permitspromptly if frightening techni-ques become inadequately effec-tive.

SRAC Publication No. 402 providesfurther information on strategies forcontrolling bird damage at aquacul-ture facilities.

Technical assistance

The Animal and Plant Health Inspec-tion Service (APHIS) of USDA canprovide technical assistance toaquacultural producers experiencinglosses to bird predators. On-siteevaluations of predation problems,recommendations on control techni-ques and strategies, and sources ofscaring equipment and supplies areavailable from APHIS AnimalDamage Control personnel. To findthe nearest Animal Damage Controloffice in your state contact your localcounty Extension agent or call theUSDA, APHIS, ADC Regional Officein Nashville, TN at (615) 736-5095.

This publication was supported in part by grants from the United States Department of Agriculture, Number 89-38500-4516, sponsored jointlyby the Cooperative State Research Service and Extension Service; The United States Fish and Wildlife Service and The United StatesDepartment of Agriculture, Animal and Plant Health Inspection Service-Animal Damage Control.