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were used together in a mix played through an acoustical
broadcast unit. Random playback order was used to delay or
reduce habitation by swallows. The presence of calls reduced From the field...Sacramento International Airport
nesting activity by more than 50%. Coates et al. (2010) eval- (FAA code--SMF)
uated bioacoustics as a deterrent to wild turkeys in Califor-
nia vineyards. Broadcast calls of three different types were Approximately 152,000 operations occur annually at
used independently: wild turkey alarm call, domestic turkey Sacramento International Airport, including commercial,
alarm, and crow distress call. No differences in damage rates cargo, general aviation, and military operations. Sacra-
were found in treated versus untreated plots. mento International Airport is located within the Nato-
Pyrotechnics
mas basin of California, situated in the Pacific migratory
flyway for numerous waterfowl and other bird species.
Pyrotechnics have long been used as deterrents to birds in Greg Rowe, senior environmental analyst, described their
a variety of settings (Neff and Mitchell 1955; Zajanc 1962; style of wildlife management as a holistic approach that
Mott 1980; Tipton et al. 1989; Mott and Boyd 1995; Andelt integrates harassment techniques and animal removal,
et al. 1997; Littauer et al. 1997; Mott and Brunson 1997) and
can be effective in deterring birds. These devices rely on an
but most important, working with land use and habitat
explosion or other type of loud noise to deter birds from an management to reduce use of the airport landscape by
area (Mott 1980) and can produce visual stimuli such as a hazardous birds. The airport employs two full-time biolo-
flash of light or burst of smoke. Devices include rifles and gists, and two other employees spend approximately half
shotguns firing live ammunition or blanks and 12-gauge of their time to reduce hazardous wildlife. Waterfowl
shotguns and flare pistols that shoot exploding or noisy pro-
jectiles, including shell crackers, bird bombs, bird whistles,
are by far the most common problem species, but other
whistle bombs, or racket bombs (Booth 1994; Harris and birds such as vultures, ibis species, and swallows are also
Davis 1998). Signal flares also have been used at some air- problematic. Additionally, raptors are a growing problem.
ports but are more expensive than the other devices (Lefeb- The most commonly employed deterrent technique is pyro-
vre and Mott 1987). An example of these devices is shown technics and electronic sound emission devices. These are
in Figure 4.
typically used to scare birds from ponds located near the
runway. Greg notes, "Our biologists typically have to ap-
ply these techniques to the same group of birds on a daily
basis in order to be effective." Greg also stressed that land
management is key and other techniques are secondary in
the mission to reduce hazards.
er-sirens were fired from single-shot pistol launchers on 4
consecutive evenings. Cormorant numbers were decreased
from approximately 8,000 birds to 6 during the harassment
period. However, Mott et al. (1992) stated that this technique
FIGURE 4 Pyrotechnics (Source : USDA/APHIS/WS Ohio would be less effective if multiple roost sites were available
Field Station). to birds in an immediate area. Logistically and financially,
harassing birds in this fashion may not be efficacious. Most
Aguilera et al. (1991) reported that screamer shells were bird species become habituated to noises produced by pyro-
effective in dispersing flocks of Canada geese; also, no technics if used repeatedly over time (Littauer et al. 1997;
habituation was reported after treatment. Mott (1980) tested Reinhold and Sloan 1997; Stevens et al. 2000; Ronconi et al.
scare cartridges and noise bombs simultaneously to disperse 2004; Ronconi and Clair 2006; Cook et al. 2008).
roosting red-winged blackbirds and European starlings in
Kentucky and Tennessee. Roosting bird populations of about
1 million birds in five roosts were reduced 96% to 100% dur- VISUAL REPELLENTS
ing 3 to 8 evenings of harassment. Mott et al. (1992) tested
the effectiveness of pyrotechnics as a dispersant for roost- Vision-based deterrents present a visual stimulus that is
ing double-crested cormorants (Phalacrocorax auritis) in novel, startling, or that the birds associate with danger. The
the Delta region of Mississippi. Bird-bangers and scream- danger can be a predator, a simulated predator, the result of
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a predator attack, or some unusual object that birds avoid Seamans (2004) reported the effective use of a vulture
because it is unfamiliar. Lights, scarecrows, dyes, reflecting effigy to deter vultures from a tower in northern Ohio. How-
tape, predator decoys, kites, balloons, smoke, and dead or ever, the author reported seasonal differences in effective-
live birds are visual stimuli that may disperse birds. ness; in the summer there was no difference in vulture use
of the tower during pre-and posttreatment periods. Seamans
Effigies and Bernhardt (2004) conducted field evaluations of Canada
goose effigies. They found an initial decrease in goose abun-
Effigies have been demonstrated to reduce bird use of target dance; however, during a second treatment period no dif-
areas; however, their efficacy varies markedly depending ference was detected. Geese were likely habituated to the
on type of effigy used, species being deterred, and resource effigies after a short time. Figure 5 shows an example of a
(nest site, loafing site, foraging area) from which birds are visual repellent in the form of a dead Canada goose.
being deterred. Effigies include devices such as scarecrows,
scary-eyes, and predator-mimicking devices (e.g., hawk or
owl) (Harris and Davis 1998). Scarecrows are one of the old-
est devices that have been used to control birds (Frings and
Frings 1967). Most scarecrows are human-shaped effigies
constructed from various inexpensive materials, includ-
ing grain sacks or old clothes stuffed with straw. The more
realistic the facial features and the human shape, the more
effective scarecrows are likely to be (Gilsdorf et al. 2002).
Painting scarecrows a bright color can increase their detect-
ability (Littauer 1990).
Stickley et al. (1995) demonstrated that a pop-up human
effigy reduced double-crested cormorant use of catfish
ponds; however, the device was only tried for 7 days. It is
unclear if habituation would have occurred later. Nomsen FIGURE 5 Dead goose effigy (Source : USDA/APHIS/WS
(1989) reported that a humanlike scarecrow that popped Ohio Field Station).
up from a double propane cannon when fired was highly
successful in keeping blackbirds from feeding over 4 to 6 Ball (2009) described in an anecdotal note that effigies
acres of sunflowers. Ducks and geese were observed to be appeared to be effective in reducing vulture use of the airfield
much easier to frighten from the site than blackbirds. Con- at Cherry Point Air Force Base in North Carolina. Similarly,
iff (1991) reported that this kind of scarecrow placed near Tillman et al. (2002) reported that effigies were effective in
a catfish pond effectively frightened cormorants. Numbers dispersing vultures from roost sites near livestock produc-
of great blue herons (Ardea herodias) and black-crowned tion facilities. Additionally, the authors tested waterfowl
night-herons (Nycticorax nycticorax) initially decreased at decoys painted to resemble dead vultures. They report a
a fish hatchery following implementation of two human effi- continued effectiveness upon switching from the taxidermy
gies (tested as Scary Man Fall Guy), but the herons quickly effigies to the mock-up decoys. Avery et al. (2002) corrobo-
habituated to the devices and numbers increased after the rated Tillman et al. (2002) in the context of vulture [black
first 4 nights (Andelt et al. 1997). Boag and Lewin (1980) vulture (Coragyps atratus) and turkey vulture (Cathartes
found that a human effigy was effective in deterring dab- aura)] use of communication towers. They found a 93%
bling and diving ducks from small natural ponds. When to 100% decline in vulture numbers immediately follow-
the effigy was present, the number of ducks on the ponds ing installation of the effigies. The authors also noted that
declined by 95%. Over the same interval there was only a effectiveness was independent of species composition of the
20% decline on adjacent control ponds, indicating that the vulture flock or the vulture species used for the effigy. Most
effigy was quite effective. important, Avery et al. (2002) found that the effectiveness
was maintained 5 months posttreatment. Effigies appear to
Cummings et al. (1986) used a propane cannon and a be an effective tool to reduce use of an area by both species
CO2 pop-up scarecrow to deter blackbirds from sunflow- of vultures.
ers. They found that most birds were frightened away by
the scarecrows; fewer birds returned during the treatment Predator Models
period than were observed during the control period. Cum-
mings et al. (1986) speculated that the birds that returned had Decoys or models have been used to repel birds for decades
become habituated to the scarecrow in some cases, and in in agricultural crops, and should be similar in the airport
other cases, that feeding patterns were too well established environment (Conover, 1979, 1982a, 1984a, 1985a; Hothem
to allow effective deterrence of the birds.
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14
and DeHaven 1982) (Table 1). Conover (1979, 1982a) found Lasers
that stationary, mounted hawks and hawk-kites deterred birds
from feeding stations and cornfields but that their effective- Lasers (such as the device shown in Figure 7) have been
ness was short-term. Conover (1984a) elucidated that hawk- demonstrated to deter birds; however, efficacy varies across
kites reduced red-winged blackbird (Aegaeileus phonecius) species and with wavelength (i.e., color) of transmitted light.
damage by 83% in an agriculture setting. Belant et al. (1998) Relative efficacy increases with decreasing ambient light.
found plastic, hand-painted effigies of great horned owls The use of lasers to disperse birds is relatively new (Lus-
(Bubo virginianus) and merlins (Falco columbarius) inef- tick 1973; Gilsdorf et al. 2002). Glahn et al. (2000) tested
fective in reducing starling use of nest boxes. There was no the efficacy of lasers to disperse double-crested cormorants
significant difference in starling activity among nest boxes from night roosts in the Mississippi Alluvial Valley during
with or without the effigies. Conover (1983) found that black- winter. Two types of lasers were tested: the DesmanTM laser
birds and crows often mob owls or owl models, increasing [red (632.8 nm) helium-neon laser] and a DissuaderTM laser
use of an area by hazardous birds. However, Conover (1982b, security device that is also a red beam (650 nm) but is a diode
1985b) found that an animated plastic owl model clutching laser (Glahn et al. 2000). The authors pretested the lasers
a plastic crow in its talons repelled crows from gardens and on wild-trapped cormorants, but results of that study were
small fields, while a stationary version of the same model inconclusive. However, the field trial portion demonstrated
was not effective. significant reductions in cormorant populations by 90%.
No difference was found between laser types.
Seamans and Helon (2006) tested a lightweight plastic
device that forms a spiral when suspended and contains pig-
ments that allow the device to change color depending on
viewing angle (tested as the ChormaFlairTM Crow Buster)
to repel starlings at nest sites. There was no difference in
the presence of nest material between treated and control
nest boxes. Also, clutch size was similar between treated and
controls, but a slight delay in egg laying was observed in the
treated boxes.
Balloons or modified balloons have been tested on
numerous occasions as a deterrent for birds in various set-
tings (Conover 1982a; Avery et al. 1988; McLennan et al.
1995; Nakamura et al. 1995; Mott et al. 1998). Seamans et
al. (2002) tested a balloon with a kite and stabilizer attached
to deter gulls near a landfill in New York. Under various
circumstances the device was effective in decreasing gull FIGURE 7 Laser used for dispersing birds (Source : USDA/
use. However, Seamans et al. (2002) reported high mainte- APHIS/WS Ohio Field Station).
nance costs and time requirements to deploy such devices.
They maintained that devices such as these should be used Blackwell et al. (2002) tested the efficacy of a 10-mW
as a part of an integrated management program for gulls. continuous-wave, 633-nm laser to repel brown-headed cow-
Figure 6 shows an example of a visual repellent in the form birds and European starlings while perching. They tested a
of a balloon. 68-mW, continuous-wave, 650-nm laser in dispersing star-
lings and rock doves from perches; also, they tested this
laser on Canada geese and mallards in grass plots. There
were mixed results; brown-head cowbirds or European star-
lings were not repelled from their perch, whereas rock doves
demonstrated avoidance during the first 5 min of the 80-min
dispersal periods, suggesting weak efficacy. Geese demon-
strated the strongest avoidance behavior, 96% of birds dis-
persed from the laser-treated plots. Mallards were dispersed
initially but habituated to the beam after 20 min.
Gorenzel et al. (2002) found similar results with Ameri-
can crows. Most crows were dispersed from roosts by the
laser, but returned within 15 min. Lasers are a relatively
FIGURE 6 Helikites in action (Source : USDA/APHIS/WS Ohio unobtrusive device to humans and show promise as a repel-
Field Station). lent for birds, but results are species specific (Blackwell et al.
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2002; Gilsdorf et al. 2002; Gorenzel et al. 2002). Although for blackbirds. However, red mirrors reduced the capture rate
green and blue lasers were ineffective at deterring white- compared with the control. Furthermore, more brown-headed
tailed deer (Odocoileus virginianus) (VerCauteren et al. cowbirds (Molothrus ater) and common grackles (Quiscalus
2006), they have not yet been tested for efficacy in repelling quiscula) were captured more often in control traps versus
birds. However, qualitative evidence at some airports sug- treated traps with mirrors.
gests green lasers can be highly effective at dispersing birds
such as rock doves and European starlings. Numerous types of lights have been used to deter birds
at feeding, roosting, and loafing sites (Koski et al. 1993;
Reflecting Tape, Reflectors, and Flags Seamans et al. 2001). Larkin et al. (1975) observed that
migrating birds reacted to searchlight beams at distances
Reflecting tape and similar devices appear to have limited of 200300 m. In the same study, birds took evasive action
efficacy in most circumstances. Summers and Hillman to approaching small aircraft with landing lights. Blackwell
(1990) tested a red fluorescent tape (20 mm wide) in fields of and Bernhardt (2004) tested the efficacy of pulsing white
winter wheat in the United Kingdom to deter brant. The tape and wavelength-specific aircraft-mounted light during day-
proved more successful than the cannon and scarecrows in light hours. Their experiments involved captive brown-head
repelling brant. Compared with control fields, a 1% reduc- cowbirds, Canada geese, European starlings, herring gulls,
tion in grain yield in the taped field was found compared with and mourning doves. Cowbirds were the only species that
a 6% reduction in the untaped field. Belant and Ickes (1997) exhibited a response to the landing lights, but responses
tested mylar flags (reflective material) for their effectiveness were sporadic. Blackwell and Bernhardt (2004) contended
as gull deterrents. Flags were tested at two nesting colonies that more research was needed on specific light wavelengths
and two loafing sites at a landfill near Lake Erie. The authors and pulse frequencies. Specifically, understanding object
concluded that the reflecting tape was unsuccessful in deter- lighting in the context of avian antipredator responses, and
ring herring gulls from nesting colonies but can reduce her- how antipredator behavior varies among bird species, may
ring and ring-billed gull use of loafing areas. Reflecting tape improve efficacy of lighting as a control technique (Black-
was ineffective in deterring birds from ripening blueberries well et al. 2009).
(Tobin et al. 1988). In this study habituation was considered
likely, and reportedly not enough tape was used to elicit a Dogs and Falconry
response. Conover and Dolbeer (1989) found similar results
with red-winged blackbirds in cornfields. Fields treated with The use of dogs to deter and haze birds is promising and gen-
reflector tape had similar damage rates to untreated fields. erally appears effective, but more experimental research is
These results contrasted with those of Dolbeer (1981), Brug- needed. The use of dogs has received attention and research
gers et al. (1986), and Dolbeer et al. (1986), who found reflec- as a tool to deter birds from airports (Carter 2000a,b; Cas-
tive tapes to be effective in grain fields. Conover and Dolbeer telli and Sleggs 2000; Patterson 2000). Castelli and Sleggs
(1989) attributed the possible differences to variation in row (2000) reported a retrospective analysis of the efficacy of a
spacing of tape. Gilsdorf et al. (2002) further suggest that border collie program to repel and haze geese. At the local
closer spacing of ribbons of tape may be more effective, but scale of the airport, the program was effective at reducing
likely not cost-effective. geese overabundance, but at the larger regional scale it did
not contribute to the solution. Carter (2000b) reported sev-
Lights and Mirrors eral case studies on the use of border collies. Most strikingly,
in Delaware the use of dogs reduced bird numbers by 99.9%,
Lights and mirrors appear to have application for dispersing and damage was reduced from $600,000/year to $24,000/
birds from airport environments, but additional research is year. Figure 8 shows an example of a dog on bird-deterrent
necessary before specific recommendations can be made. Few duty at an airport.
studies have evaluated the effectiveness of mirrors to deter
birds. Seamans et al. (2001) evaluated mirrors to deter nesting
starlings in northern Ohio. Various combinations of mirror
types and the addition of lights (green and red flashing) were
tested. Fewer nests were found in treated nest boxes in the first
year of study. During the second year lower occupancy rates
of nest boxes were also found, specifically in the mirror and
light combination treatment. The authors concluded that even
though slight reduction in starling use was found, mirrors
were not a practical repellent. Seamans et al. (2003) followed
up the previous study with a similar experiment testing rotat-
ing mirrors as a deterrent for decoy traps. Capture rates did not FIGURE 8 Border collie at work in Florida [Source : Marc
differ between treated (rotating mirror) and untreated traps Beaudin, The News-Press (Ft. Myers, Fla.)].
