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HOW BIRDS INTERPRET DISTRESS CALLS: IMPLICATIONS FOR APPLIED USES OF DISTRESS CALL PLAYBACKS

  • February 1994
Authors:
Michael R. Conover at Utah State University
Michael R. Conover
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Abstract

Distress call playbacks are used as deterrents to keep birds out of areas where they are causing problems. However, the calls often are ineffective, owing to birds' rapid habitation to them. Recent studies on the functional significance of distress calls indicate that adult passerines only distress call when physically constrained and that the calls are designed to startle the predator holding the caller into releasing it. Further, distress calls attract other birds, which approach the caller to acquire information about the predator. These findings suggest that distress calls would be more effective if their broadcast is paired with a predator model that appears to be grasping the caller. Such a pairing should reinforce a bird's fear of the predator model and delay its habituation to the distress call.
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Proceedings of the Sixteenth Vertebrate Pest
Conference (1994) Vertebrate Pest Conference Proceedings collection
2-17-1994
HOW BIRDS INTERPRET DISTRESS CALLS:
IMPLICATIONS FOR APPLIED USES OF
DISTRESS CALL PLAYBACKS
Michael R. Conover
Berryman Institute and Wildlife Damage Management Program, Department of Fisheries and Wildlife, Utah State University,
Logan, Utah
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Conover, Michael R., "HOW BIRDS INTERPRET DISTRESS CALLS: IMPLICATIONS FOR APPLIED USES OF DISTRESS
CALL PLAYBACKS" (1994). Proceedings of the Sixteenth Vertebrate Pest Conference (1994). Paper 12.
hp://digitalcommons.unl.edu/vpc16/12
HOW BIRDS INTERPRET DISTRESS CALLS: IMPLICATIONS FOR APPLIED USES OF
DISTRESS CALL PLAYBACKS
MICHAEL R. CONOVER, Berryman Institute and Wildlife Damage Management Program, Department of Fisheries
and Wildlife, Utah State University, Logan, Utah 84322-5210.
ABSTRACT: Distress call playbacks are used as deterrents to keep birds out of areas where they are causing problems.
However, the calls often are ineffective, owing to birds' rapid habitation to them. Recent studies on the functional
significance of distress calls indicate that adult passerines only distress call when physically constrained and that the calls
are designed to startle the predator holding the caller into releasing it. Further, distress calls attract other birds, which
approach the caller to acquire information about the predator. These findings suggest that distress calls would be more
effective if their broadcast is paired with a predator model that appears to be grasping the caller. Such a pairing should
reinforce a bird's fear of the predator model and delay its habituation to the distress call.
Proc. 16th Vertebr. Pest Conf. (W.S. Halverson& A.C. Crabb,
Eds.) Published at Univ. of Calif., Davis. 1994.
INTRODUCTION
Distress call playbacks have been used for decades to
keep birds out of areas where they are causing problems
(Frings and Jumber 1954, Frings et al. 1955). Their
ability to repel birds has been evaluated in agricultural
fields (Boudreau 1975, Naef-Daenzer 1983, Summers
1985), airports (Blokpoel 1976), fish ponds (Spanier
1980), and roosts (Pearson et al 1967, Brough 1969).
Usually, distress call playbacks effectively deter birds for
only a few days or weeks before habituation sets in.
Hence, distress call playbacks are most effective for
short-term problems such as protecting a ripening field
that will be harvested in a few days or in dispersing a
group of birds that are migrating through an area.
Before distress call playbacks can live up to their
potential of alleviating longer-term problems, we need to
know why birds habituate rapidly to them and what can
be done to delay this process. In this regard, we must
understand why birds distress call and how other birds,
who hear a distress call, interpret it and what they expect
to find when they approach the caller.
FUNCTIONAL SIGNIFICANCE OF DISTRESS CALLS
Distress calls are emitted by adult birds which are
physically constrained by a predator (Schmidt and Johnson
1984) and are distinctive from alarm calls (Thompson et
al. 1968; Stefanski and Falls 1972a, 1972b; Starkey and
Starkey 1973). Two major hypotheses have been
proposed to explain why an adult bird facing imminent
predation should distress call. The startle-the-predator
hypothesis states that a bird distress calls to startle the
predator into releasing it (Driver and Humphries 1969),
The other hypothesis is that distress calls are designed to
attract attention to the caller (attract-attention
hypothesis). There actually are four subcategories of this
hypothesis that differ in whose attention the caller is
trying to attract and what the intended recipient is suppose
to do when it arrives. The request-aid hypothesis states
that a bird distress calls to solicit the aid of kin or other
birds (reciprocal altruists) to help it escape.
The warn-kin hypothesis assumes that distress calls
are designed to warn kin about the dangerous predator
that has captured the caller and hence to increase the kin's
probability of surviving. This hypothesis argues that
distress calling does not increase the caller's chances of
surviving the predator attack but does enhance the caller's
inclusive fitness by increasing the probability of its kin
avoiding a similar fate.
The attract-an-audience hypothesis assumes that birds
can gain valuable information by witnessing a predator-
prey interaction and use that information to avoid
predation in the future (Conover 1987). This hypothesis
states that sometimes the predator's best interest is to
release a victim rather than attract the attention of too
many birds. This hypothesis is supported by the finding
that birds can acquire information from watching
predator-prey interactions (Kruuk 1976, Curio et al. 1978,
Conover and Perito 1981, Conover 1984, Shields 1984,
Conover 1987).
The attract-another-predator hypothesis argues that
distress calls are given to attract a second predator that
will threaten or disturb the predator which has seized the
caller, allowing the latter an opportunity to escape. This
hypothesis is supported by the observations that distress
calls sometimes attract predators (Perrone 1980, Hogstedt
1983, Koenig et al. 1991).
Recent experiments support the startle-the-predator
hypothesis. Some captive raccoons (Procyon lotor) and
opossums (Didelphis marsupialis) that were attacking a
caged starling (Sturnus vulgaris) were startled when a
distress call was first broadcast, and they released the bird
(Conover, in press). Prior to the call's onset, these
predators exhibited no such behavior.
Conover (in press) demonstrated that distress calls
usually consisted of a brief series of notes less than five
seconds in duration and that these were followed by
periods of silence before another distress call was
initiated. This pattern was consistent with the startle-the-
predator hypothesis, but the attract-attention hypothesis
predicted long and continuous calls to increase the
chances that the intended recipient would be able to hear
the caller and locate it.
Conover (in press) also showed that birds are more
likely to distress call when they have an opportunity to
escape from the predator's grasp, as expected with the
startle-the-predator hypothesis. For instance, birds
distress call more when held loosely or by their limbs
than when held securely by the body or neck. These data
233
support the startle hypothesis. In contrast if the only
function of a distress call were to attract attention, then a
bird should distress call more when held securely by the
body or head because its chances of escaping on its own
are diminished and its need for aid is increased.
IMPLICATIONS FOR THE USE OF DISTRESS CALL
PLAYBACKS TO SCARE BIRDS FROM PROBLEM
AREAS
Upon hearing a distress call, birds usually approach
the caller rather than flee or hide. They do not usually
attack the predator or engage in any behavior that would
aid the caller, but rather they observe the predator
(Conover, in press). Birds engage in this behavior to
acquire information about the predator and are able to use
this information to reduce their own chances of falling
prey in the future (Conover and Perito 1981, Conover
1987, Conover, in press).
Such findings indicate that birds, which approach the
sound source when they hear a distress call playback, are
expecting to see a bird being physically constrained by a
predator. However, wildlife damage managers rarely pair
distress call playbacks with predator models or other
visual stimuli. This lack of pairing may reduce the
effectiveness of distress calls and allow birds to habituate
to their playback more rapidly than would otherwise be
the case. If distress call playbacks are paired with a
predator model, especially one that appear to be grasping
the caller, birds that approach the sound source might
have their initial fears reinforced rather than alleviated.
Support for this hypothesis comes from the findings that
starlings and American crows (Corvus branchyrhynchos)
habituated less to plastic owl models when the models
appeared to be grasping a struggling bird in their talon
(Conover and Perito 1981, Conover 1984).
LITERATURE CITED
BLOKPOEL, H. 1976. Bird hazards to aircraft. Books
Canada Inc., Buffalo, N.Y., 235 pp.
BOUDREAU, G. W. 1975. How to win the war with
pest birds. Wildlife Technology, Hollister, Calif. 174
pp.
BROUGH, T. 1969. The dispersal of starlings from
woodland roosts and the use of bio-acoustics. J.
Appl. Ecol. 6:403-410.
CONOVER, M. R. 1984. Protecting vegetables from
crows using an animated crow-killing owl model. J.
Wildl. Manage. 49:643-645.
CONOVER, M. R. 1987. Acquisition of predator
information by active and passive mobbers in ring-
billed gull colonies. Behav. 102:41-57.
CONOVER, M. R., and J. J. PERITO 1981. Response
of starlings to distress calls and predator models
holdingconspecific prey. Z. Tierpsychol. 57:163-172.
CONOVER, M. R. In press. Stimuli eliciting distress
calls in adult passerines and response of predators and
birds to their broadcast. Behav.
CURIO, E., U. ERNST, and W. VIETH. 1978. The
adaptive significance of avian mobbing. II. Cultural
transmission of enemy recognition in blackbirds:
effectiveness and some constraints. Z. Tierpsychol.
48:184-202.
DRiyER, P. M., and D. A. HUMPHRIES. 1969. The
significance of the high-intensity alarm call in
captured passerines. Ibis 111:243-244.
FRINGS, H., and J. JUMBER. 1954. Preliminary
studies on the use of a specific sound to repel
starlings (Sturnus vulgaris) form objectionable roosts.
Science 119:318.
FRINGS, H., M. FRINGS, B. COX, and L. PEISSERR.
1955. Recorded calls of herring gulls (Larus
argentatus) as repellents and attractants. Science
121:340-341.
HOGSTEDT, G. 1983. Adaption unto death: function of
fear screams. Am. Nat. 121:562-570.
KOENIG, W. D., M. T. STANBACK, and P. N.
HOOGE. 1991. Distress calls in the acorn
woodpecker. Condor 93:637-643.
KRUUK, H. 1976. The biological function of gulls
attraction towards predators. Anim. Behav. 24:146-
153.
NAEF-DAENZER, L. 1983. Scaring of carrion crows
{Corvus corone corone) by species-specific distress
calls and suspended bodies of dead crows. Proc. Bird
Control Seminar 9:91-95.
PEARSON, E. W., P. R. SKON, and G. W. CORNER.
1967. Dispersal of urban roosts with records of
starling distress calls. J. Wildl. Manage. 31:502-506.
PERRONE, M. JR. 1980. Factors affecting the
incidence of distress calls in passerines. Wilson Bull.
92:404-408.
SCHMIDT, R. H., and R. J. JOHNSON. 1984. Bird
dispersal recordings: an overview. In Vertebrate Pest
Control and Management Materials: Fourth
Symposium. Am. Soc. Testing Materials, Special
Tech. Publ. 817:43-65.
SHIELDS, W. M. 1984. Barn swallow mobbing: self
defense, collateral kin defense, group defense, or
parental care? Anim. Behav. 32:132-148.
SPANIER, E. 1980. The use of distress calls to repel
night herons (Nycticorax nycticorax) from fish ponds.
J. Appl. Ecol. 17:287-294.
STARKEY, E. E., and J. F. STARKEY. 1973.
Description of an aerial predator alarm call for
mallard (Anas platyrhynchos) ducklings. Condor
75:364-366.
STEFANSKI, R. A., and J. B. FALLS. 1972a. A study
of distress calls of song, swamp, and white-throated
sparrows (Aves: Fringillidae). I. Intraspecific
responses and functions. Can. J. Zool. 50:1501-
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STEFANSKI, R. A., and J. B. FALLS. 1972b. A study
of distress calls of song, swamp, and white-throated
sparrows. II. Interspecific responses and properties
used in recognition. Can. J. Zool. 50:1513-1525.
SUMMERS, R. W. 1985. The effect of scarers on the
presence of starlings (Sturnus vulgaris) in cherry
orchards. Crop Protection 4:520-528.
THOMPSON, R. D., C. V. GRANT, E. W. PEARSON,
and G. W. CORNER. 1968. Differential heart rate
response of starlings to sound stimuli of biological
origin. J. Wildl. Manage. 32:888-893.
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