An Introduction to Songs and Calls

Songs and Calls

The vocalizations of birds can be divided into two broad categories: songs and calls (Catchpole and Slater 1995).  Songs tend to be complex, usually multisyllabic, often musical, and are generally learned by young individuals from adults that they hear and imitate.  They are used in territory establishment and defense, mate attraction, and to discourage potential rivals.  Calls tend to be structurally simpler, often monosyllabic, and have historically been thought to develop innately.  Calls are given in a wide range of contexts, but most calls can be placed into one of several categories: alarm call, contact call, roosting call, food call, begging call, or agonistic call (Marler 2004).  With the wide range of information that can be transmitted, studies of calls have taught us a great deal about communication and social structure in avian populations.  However, calls have historically been the focus of much less intense study than songs, and there is much that remains to be learned.  The diversity in repertoire, the levels of species specificity in particular calls and how this level changes with the category of call and the context in which it is given, and the selective pressures on both the call sender and receiver are all areas that warrant further and more detailed investigation.

Functions and Structure of Different Calls

Alarm Calls – Alarm calls can be divided into three subcategories – flee alarm, assembly alarm, and alert calls; calls in these subcategories tend to elicit different responses (Bradbury and Vehrencamp 1998).  The flee alarm is a signal sent to nearby individuals and tends to cause receivers to move rapidly away from the sender and/or to seek cover.  In many species, this signal can vary depending on the type of threat detected (aerial predator vs. terrestrial predator for example) and also on the proximity of the predator (Leavesley and Magrath 2005).  White-browed Scrubwrens (Sericornis frontalis) have been shown to increase the number of elements in their flee call with proximity of a suddenly appearing predator, and flee calls with larger numbers of elements also prompted more urgent responses in receivers (Leavesley and Magrath 2005).  Distress calls are an extreme form of flee alarm usually only given when an individual finds itself severely threatened.  These calls are loud, usually include a harsh rasping or screaming quality, and are often repeated rapidly.  Some evidence suggests that birds may give a distress call, when it is being attacked by a predator, to attract other predators with the result being that the new predator will compete with, and possibly drive off the current predator and so allow the prey to escape in the confusion (Koenig et al. 1991).  In some species the distress call attracts other members of the same species, and sometimes members of other species as well, that may then attempt to drive off the predator (Chu 2001, pers. obs.).

The assembly alarm (often calls a “mobbing call”, Bradbury and Vehrencamp 1998) is typically produced when a predator is located, causing receivers that are more widely dispersed to move toward the sender.  The information that is conveyed by these calls can not only include the location of the sender, but the location and type of threat as well.  This was demonstrated by Templeton et al. (2005), where presentation experiments revealed that Black-capped Chickadees (Poecile atricapilla) varied their mobbing calls, and their responses to these calls, in response to predator body size.

Calls that fall somewhere between the extremes of flee alarms and assembly alarms are alert calls.  These signals do not tend to cause receivers to move.  They are hypothesizes to inform other individuals of possible threats or other changes in the local environment (Seyfarth et al. 1980).  They may also be used to tell predators that they have been detected causing the predator to hunt other, less vigilant, prey (Caro 1995).  Studies suggest that when a local prey population has been alerted to the presents of a predator, the predator is less likely to succeed in its attempts to capture prey (Bergstrom and Lachmann 2001, Zuberbühler et al. 2009).

Each of these categories of alarm call can contain multiple distinct vocalizations.  Heterospecifics may also perceive and respond to these calls (Hurd 1996, Nolan and Lucas 2009).  For different species to correctly interpret a signal, that signal must have certain characteristics that cause it to be recognized by a wide and varying group.  Such characteristics may include relatively low variability and/or acoustic characteristics that are common to many species.  An example of common characteristics is given by Jurisevic and Sanderson (1994) who found that of the 30 species of bird examined, representing a wide range of taxa, 29 of them produced an alarm call with broad frequency range and a noisy or harmonic structure.  These calls do differ in area of active space, the area over which a call can be detected (Brenowitz 1982).  Flee calls are sent when danger is immediate and received by individuals that are close by (Magrath et al 2007).  Both of these conditions encourage the sender to vocalize relatively quietly and so improve the odds of the sender avoiding detection.  Distress calls are an exception to this in that they are loud, harsh sounds that may cause a predator to startle and stop the attack (Laiolo et al 2004, pers. obs.).  Assembly calls, contrastingly, attract individuals from some distance away, and so need to be louder than standard flee calls (Johnson et al 2003).  They must easily localizable using binaural cues or provide information about the location of the sender in order to effectively elicit a mob (Templeton et al. 2005).

Contact Calls – Contact calls are used by individuals of both sexes throughout the year and are thought to facilitate group cohesion, keeping group members in acoustic and/or visual contact.  They have a wide range of variation depending on the distance between the individual and the rest of the group and also depending on who is separated from whom.  They can be unique to individuals, allowing specific communication between particular individuals (Dooling et al. 1992, Bradbury 2003).  Contact calls may provide information to receivers about the approximate distance and activity level of the sender (Dooling et al. 1992).  The sound characteristics of, and response to, these calls are generally species specific (Wanker and Fischer 2001, Sharp and Hatchwell 2005).

Flight calls are a special form of contact call.  These calls are given while a flock is preparing to take flight and also during flights, and are hypothesizes to signal and coordinate group movements.  Flight calls are given by both sexes throughout the year, but are usually much louder than most other contact calls.  They can also be used to identify group membership and individual identity.  Mundinger (1970) found that female American Goldfinches (Carduelis tristis) could discriminate between the flight calls of their mate and those of other males.  Balsby and Bradbury (2009) found that Orange-fronted Conures (Aratinga canicularis) used their ‘chee’ call when two flocks were approaching one another to orchestrate flock fission or fusion.

Individual discrimination requires that a particular bird gives their own variant of a call with consistency in at least some acoustic features so as not to be confused with other individuals (Berg et al. 2010).  It also necessitates a wide range in variation across the whole population to allow for so many discrete variant to exist in acoustic space (Wanker and Fischer 2001).

Roosting Calls – Many species of bird vocalize as they are settling into night roosts.  Some tend to be sent over short distances such as a female calling her young to where she has settled for the night (Collias and Joos 1953).  Others tend to be sent over larger distances such as in a large flock of birds, like those observed in blackbirds or crows which gather together in the evening at a roost site (Hill and Lein 1985).  It is thought that members of these large flocks can gain information about local resources by how the flock breaks up each morning (Ward and Zahavi 1973, Buckley 1996, Dall 2002).  In this way, roosting calls serve as a way for individuals to locate flocks and so be in a position to benefit from the flocks’ collective knowledge the next morning.

Food Calls – Food calls are produced when the sender locates a food source (Elgar 1986, Buitron and Nuechterlein 1993), and may function to advertise a food find to receivers.  Senders may benefit for producing these calls, since receivers are typically young or close relatives of the sender, or potential mates (Buitron and Nuechterlein 1993).  For example, male domestic chickens are more likely to give food calls when there is another chicken nearby than when they are alone (Evans and Marler 1994), indicating that the calls have a communication function and are not simply a response to food.  Food calls are also more common when the nearby chicken is female which indicates the use of food calls in courtship (Marler et al 1991).  Some males have been observed to give food calls when holding a non-food item such as a stick, but only when the female is some distance away.  These males seem to be attempting to deceive the female with a false attractant which can only be detected as such with close proximity (Gyger and Marler 1988).    For food calls to be effective, therefore, the sender must be locatable and must be identifiable to individual; locatable so that the other birds can determine where the food source is, and identifiable to individual so that they can possibly assess the trustworthiness of the sender (Gyger and Marler 1988).  Birds outside of Galliformes rarely produce food calls and when they do occur it is usually around an extremely abundant food source (Elgar 1986, Heinrich 1989, Brown et al. 1991, Mahurin and Freeberg 2009).

Begging Calls – Begging calls are given most commonly by young to adults to elicit feeding (Godfrey 1991).  To be effective, adults must be able to locate and identify their own young.  In solitarily nesting species adults do discriminate between individual nestlings (Redondo and De Reyna 1988), but they have no need of discriminating between their own young and those of a different adult because when they return to the area of their nest, their own young are the only young present.  However, in colony nesting species, the task for an adult to correctly identify its own offspring out of a group of nests or young birds becomes much more challenging.  Beecher (1989, 1990) showed that individual nestling Barn Swallows (Hirundo rustica), which nest apart from one another, have much less stereotypy in their begging calls than do nestling Bank Swallows (Riparia riparia), which nest colonially.  Beecher argued that each Bank Swallow nestling must produce its own particular begging call variation very consistently so as not to overlap with its neighbors.  However, as a whole, a Bank Swallow colony will have many more begging call variants than a comparable number of solitarily nesting Barn Swallows, which can have overlapping begging call from nest to nest.  These studies serve to illustrate how the amount of variation, in terms of acoustic properties of a call in acoustic space, within an individual is related to how close the nearest neighbor is in terms of the same acoustic space.  Birds that have many other individuals close by must be very specific in the calls they give to avoid being confused with their neighbors, whereas bird that has no close neighbors is not so constrained.

Agonistic Calls – Aggressive behavioral interactions frequently include vocalizations, referred to as agonistic calls.  These calls can be given at any time of year, and are typically used to drive off, or decide the fighting ability and/or vigor of, the receiver.  Receivers can be other individuals of the same species, other species of bird, or even non-avian intruders.  These calls are usually harsh sounds and have a fairly large degree of variability, are usually given at close range, and do not contain information on the location of the sender (Black and Owen 2004).

Cited Literature

Balsby, T.J.S. and Bradbury, J.W., 2009. Vocal matching by orange-fronted conures (Aratingacanicularis). Behavioral Processes 82, 133-139.

Beecher, M.D., 1989. Signaling systems for individual recognition: An information theory approach. Animal Behavior 38, 248-261.

Beecher, M.D., 1990. “The evolution of parent-offspring recognition in swallows.”  In: Contemporary Issues in Comparative Psychology. Dewsbury, D. Sinauer Associates, Sunderland, MA.

Berg, K.S., Delgado, S., Okawa, R., Beissinger, S.R., and Bradbury, J.W. 2010. Contact calls are used for individual mate recognition in free-ranging green-rumped parrotlets, Forpus passerinus. Animal Behaviour 81, 241-248.

Bergstrom, C.T. and Lachmann, M. 2001. Alarm calls as costly signals of antipredator vigilance: the watchful babbler game. Animal Behaviour 61, 55-543.

Black, J.M. and Owen, M. 2004. Agonistic behavior in barnacle goose flocks: assessment, investment and reproductive success. Animal Behaviour 37, 199-209.

Bradbury, J.W. 2003. “Vocal communication in wild parrots.” In: Animal Social Complexity: Intelligence, Culture and Individualized Societies. DeWaal, F.B.M. and Tyack, P.L. Harvard University Press, Cambridge, MA.

Bradbury, J.W. and Vehrencamp, S.L. 1998. Principales of animal communication. Sinauer Associates, Sunderland, MA.

Brenowitz, E.A. 1982. The active space of red-winged blackbird song. Journal of Comparative Physiology 147, 511-522.

Brown, C.R., Brown, M.B., and Shaffer, M.L. 1991. Food-sharing signals among socially foraging cliff swallows. Animal Behaviour 42, 551-564.

Buckley, N.J. 1996. Food finding and the influence of information, local enhancement, and communal roosting on foraging success of North American vultures. Auk 113, 473-488.

Buitron, D. and Nuechterlein, G.L. 1993. Parent-young vocal communication in eared grebes. Behaviour 127, 1-20.

Caro, T.M. 1995. Pursuit-deterrence revisited. Trends in Ecology and Evolution 10, 500-503.

Catchpole, C.K. and Slater, P.J.B. 1995.Bird song: biological themes and variations. Cambridge University Press, Cambridge, MA.

Chu, M. 2001. Heterospecific responces to scream calls and vocal mimicry by phainopepla (Phainopeplanitens) in distress. Behaviour 138,775-787.

Collias, N.E. and Joos, M. 1953. The spectrographic analysis of sound signals of the domestic fowl. Behaviour 5, 175-188.

Dall, S.R.X. 2002. Can information sharing explain recruitment to food from communal roosts? Behavioral Ecology 13, 42-51.

Dooling, R.J., Brown, S.D., Klump, G.M., and Okanoya, K. 1992. Auditory perception of conspecific and heterospecific vocalizations in birds: evidence for special processes. Journal of Comparative Psychology 106, 20-28.

Elgar, M.A. 1986. House sparrows establish foraging flocks by giving chirrup calls in the resource is divisible. Animal Behaviour 34, 169-174.

Evans, C.S. and Marler, P. 1994. Food calling and audience effect in male chickens, Gallus gallus: their relationships to food availability, courtship and social facilitation. Animal Behaviour 47, 1159-1170.

Godfrey, H.C.J. 1991. Signaling of need by offspring to their parents. Nature 352, 328-330.

Gyger, M. and Marler, P. 1988. Food calling in the domestic fowl, Gallus gallus: the role of external referents and deception. Animal Behaviour 36, 358-365.

Heinrich, B. 1989.Ravens in Winter. Simon and Schuster, NY.

Hill, B.G. and Lein, M.R. 1985. The non-song vocal repertoire of the white-crowned sparrow. Condor 87, 327-335.

Hurd, C.R. 1996. Interspecific attraction to the mobbing calls of black-capped chickadees (Parusatricapillus). Behavioral Ecology and Sociobiology 38, 287-292.

Johnson, F.R., McNaughton, E.J., Shelley, C.D., and Blumstein, D.T. 2003. Mechanisms of heterospecific recognition in avian mobbing calls. Australian Journal of Zoology 51, 577-585.

Jurisevic, M.A. and Sanderson, K.J. 1994. Alarm vocalizations in Australian birds: convergent characteristics and phylogenetic differences. Emu 94, 69-77.

Koenig, W.D., Stanback, M.T., Hooge, P.N., and Mumme, R.L. 1991. Distress calls in the acorn woodpecker. Condor 93, 637-643.

Laiolo, P., Tella, J.L., Carrete, M., Serrano, D., and Lopez, G. 2004. Distress calls may honestly signal bird quality to predators. Proc. R. Soc. Lond. B (Suppl.) 271,S513-S515.

Leavesley, A.J. and Magrath, R.D. 2005.Communicating about danger: urgency alarm calling in a bird. Animal Behaviour 70, 365-373.

Magrath, R.D., Pitcher, B.J., and Gardner, J.L. 2007. A mutual understanding? Interspecific responses by birds to each other’s aerial alarm calls. Behavioral Ecology 18, 944-951.

Mahurin, E.J. and Freeberg, T.M. 2009. Chick-a-dee call variation in Carolina chickadees and recruiting flockmates to food. Behavioral Ecology 20, 111-116.

Marlar, P. 2004.“Bird calls: a cornucopia for communication.” In: Nature’s Music: the science of birdsong. P. Marler and H. Slabbekoorn, Elsevier Academic Press, New York, NY.

Marler, P., Karakashian, S. and Gyger, M. 1991. “Do animals have the option of withholding signals when communication is inappropriate? The audience effect.” In: Cognitive Ethology: The Minds of Other Animals. C. Ristau, Lawrence Erlbaum, Hillsdale, NJ.

Mundinger, P.C., 1970. Vocal imitation and individual recognition of finch calls. Science 168, 480-482.

Nolan, M.T. and Lucas, J.R. 2009. Asymmetries in mobbing behaviors and correlated intensity during predator mobbing by nuthatches, chickadees and titmice. Animal Behaviour 77, 1137-1146.

Redondo, T. and De Reyna, L.A. 1988.Locatability of begging calls in nestling altricial birds. Animal Behaviour 36, 653-661.

Seyfarth, R.M., Cheney, D.L., and Marler, P. 1980. Monkey responses to three different alarm calls: evidence of predator classification and semantic communication. Science 210, 801-803.

Sharp, S.P. and Hatchwell, B.J. 2005. Individuality in the contact calls of cooperatively breeding long-tailed tits (Aegithalos caudatus). Behaviour 142, 1559-1575.

Templeton, C.N., Greene, E., and Davis, K. 2005. Allometry of alarm calls: black-capped chickadees encode information about predator size. Science 308, 1934-1937.

Wanker, R., and Fischer, J. 2001. Intra- and interindividual variation in the contact calls of spectacled parrotlets (Forpus conspicillatus). Behaviour 138, 709-726.

Ward, P. and Zahavi, A. 1973. The importance of certain assemblages of birds as “information-centers” for food-finding. Ibis 115, 517-534.

Zuberbühler, K., Jenny, D., and Bshary, R. 2009. The predator deterrence function of primate alarm calls. Ethology 105, 477-490.