Adult Richardson's Ground Squirrels (Spermophilus richardsonii) Ignore Rate Changes in Juvenile Alarm Calls: Age‐Differential Response Urgency Perception?

Juvenile Richardson's ground squirrels (RGS; Spermophilus richardsonii) communicate response urgency by modulating the rate of syllable production in repetitive alarm calls, although longer call bouts do not promote more pronounced or longer‐lasting (tonic) vigilance in juvenile call recipients. We exposed free‐living adult RGS to playbacks of alarm calls differing in rate and length to determine whether adult receivers respond to the same alarm parameters as juveniles. Adult squirrels did not respond differentially to differences in call rate or length, suggesting that adult RGS do not attend to call rate as do juveniles. This difference in response may be attributable to a developmental change in the perceptual mechanisms by which individuals extract information regarding response urgency, but could also be a product of adult receivers devaluing information encoded in alarm calls emitted by relatively inexperienced juvenile signalers.     

Monotony and the Information Content of Richardson's Ground Squirrel (Spermophilus richardsonii) Repeated calls: Tonic Communication or Signal Certainty?

The repetition of elements within an alarm signal is commonly thought to ensure that receivers have detected that signal, or to promote residual vigilance in light of the dangerous circumstances prompting the signal's initial production (tonic communication). Beyond alerting others and maintaining that state of alertness, however, repetitive signal elements may be parsed so as to encode information about the nature of potential threats. To determine how call length and variation in intersyllable latency might prove informative in the repetitive alarm vocalizations of Richardson's ground squirrels (Spermophilus richardsonii), we conducted a field‐based playback experiment quantifying antipredator responses to manipulated alarm calls. Free‐living juvenile squirrels were exposed to playbacks of 12 syllable (long) and six syllable (short) calls with a constant (monotonous) or changing (variable) call rate. The length of calls had no significant effect on the behaviour of call recipients during and immediately after call production; however, call recipients showed greater vigilance after the playback of monotonous calls than after variable calls. The absence of a call length effect is not consistent with tonic communication in the strict sense; rather, enhanced responsiveness to monotonous relative to variable calls suggests that multiple syllables, and the emergent patterns of intersyllable latency, communicate information about response urgency or the distance to a predatory threat. Only monotonous calls convey those aspects with any certainty on the part of the signaller and hence are selectively attended to by receivers.     

The acoustic structure of suricates'' alarm calls varies with predator type and the level of response urgency.

The variation in the acoustic structure of alarm calls appears to convey information about the level of response urgency in some species, while in others it seems to denote the type of predator. While theoretical models and studies on species with functionally referential calls have emphasized that any animal signal considered to have an external referent also includes motivational content, to our knowledge, no empirical study has been able to show this. In this paper, I present an example of a graded alarm call system that combines referential information and also information on the level of urgency. Acoustically different alarm calls in the social mongoose Suricata suricatta are given in response to different predator types, but their call structure also varies depending on the level of urgency. Low urgency calls tend to be harmonic across all predator types, while high urgency calls are noisier. There was less evidence for consistency in the acoustic parameters assigned to particular predator types across different levels of urgency. This suggests that, while suricates convey information about the level of urgency along a general rule, the referential information about each category of predator type is not encoded in an obvious way.     

Age Differences in the Response of California Ground Squirrels (Spermophilus beecheyi) to Conspecific Alarm Calls

Juvenile California ground squirrel responses to adult alarm calls and juvenile alarm calling may be modified during development to achieve adult form. Adult conspecific chatter and whistle alarm calls were played back to juvenile and adult ground squirrels at an agricultural field site. In response to chatter playbacks, adults spent more time visually orienting to the environment and less time out of view and in covered habitats than juveniles; the converse was true in response to whistle playbacks. To test the evocativeness of juvenile calling, a subset of adult subjects received juvenile chatter and whistle playbacks. Adults spent less time out of view to juvenile call types than to adult calls, and showed more similar responses to juvenile chatters and whistles than to adult chatters and whistles. Age differences in the ground squirrel's alarm call system may reflect adjustments to changing risks during development.     

The versatility of graded acoustic measures in classification of predation threats by the tufted titmouse Baeolophus bicolor: exploring a mixed framework for threat communication

Many mammal and bird species respond to predator encounters with alarm vocalizations that generate risk‐appropriate responses in listeners. Two conceptual frameworks are typically applied to the information encoded in alarm calls and to associated anti‐predator behaviors. ‘Functionally referential’ alarm systems encode nominal classes or categories of risk in distinct call types that refer to distinct predation‐risk situations. ‘Risk‐based’ alarms encode graded or ranked threat‐levels by varying the production patterns of the same call types as the urgency of predation threat changes. Recent work suggests that viewing alarm‐response interactions as either referential or risk‐based may oversimplify how animals use information in decision‐making. Specifically, we explore whether graded alarm cues may be useful in classifying risks, supporting a referential decision‐making framework. We presented predator (hawk, owl, cat, snake) and control treatments to captive adult tufted titmice Baeolophus bicolor and recorded their vocalizations, which included ‘chick‐a‐dee’ mobbing calls (composed of chick and D notes), ‘seet’ notes, two types of contact notes (‘chip’, ‘chink’), and song. No single call type was uniquely associated with any treatment and the majority of acoustic measures varied significantly among treatments (46 of 60). The strongest models (ANOVA and classification tree analysis) grouped hawk with cat and owl, and control with snake, and were based on the number or proportion of a) chick and D notes per chick‐a‐dee call, b) chip versus chink notes produced following treatment exposure, and c) the frequency metrics of other note types. We conclude that (1) the predation‐threat information available in complex titmouse alarm calls was largely encoded in graded acoustic measures that were (2) numerous and variable across treatments and (3) could be used singly or in combinations for either ranking or classification of threats. We call attention to the potential use of mixed threat identification strategies, where risk‐based signal information may be used in referential decision‐making contexts.     

Age Differences in the Responses to Adult and Juvenile Alarm Calls by Bonnet Macaques (Macaca radiata)

This study examined the differential responses to alarm calls from juvenile and adult wild bonnet macaques ( Macaca radiata ) in two parks in southern India. Field studies of several mammalian species have reported that the alarm vocalizations of immature individuals are often treated by perceivers as less provocative than those of adults. This study documents such differences in response using field-recorded playbacks of juvenile and adult alarm vocalizations. To validate the use of playback vocalizations as proxies of natural calls, we compared the responses of bonnet macaques to playbacks of alarm vocalizations with responses engendered by natural alarm vocalizations. We found that the frequency of flight, latency to flee, and the frequency of scanning to vocalization playbacks and natural vocalizations were comparable, thus supporting the use of playbacks to compare the effects of adult and juvenile calls. Our results showed that adult alarm calls were more provocative than juvenile alarm calls, inducing greater frequencies of flight with faster reaction times. Conversely, juvenile alarm calls were more likely to engender scanning by adults, a result interpreted as reflecting the lack of reliability of juvenile calls. Finally, we found age differences in flight behavior to juvenile alarm calls and to playbacks of motorcycle engine sounds, with juveniles and subadults more likely to flee than adults after hearing such sounds. These findings might reflect an increased vulnerability to predators or a lack of experience in young bonnet macaques.     

Functionally Referential Alarm Calls in Tamarins (Saguinus fuscicollis and Saguinus mystax) – Evidence from Playback Experiments

Studies on primate vocalisation have revealed different types of alarm call systems ranging from graded signals based on response urgency to functionally referential alarm calls that elicit predator‐specific reactions. In addition, alarm call systems that include both highly specific and other more unspecific calls have been reported. There has been consistent discussion on the possible factors leading to the evolution of different alarm call systems, among which is the need of qualitatively different escape strategies. We studied the alarm calls of free‐ranging saddleback and moustached tamarins (Saguinus fuscicollis and Saguinus mystax) in northeast Peru. Both species have predator‐specific alarm calls and show specific non‐vocal reactions. In response to aerial predators, they look upwards and quickly move downwards, while in response to terrestrial predators, they look downwards and sometimes approach the predator. We conducted playback experiments to test if the predator‐specific reactions could be elicited in the absence of the predator by the tamarins’ alarm calls alone. We found that in response to aerial alarm call playbacks the subjects looked significantly longer upwards, and in response to terrestrial alarm call playbacks they looked significantly longer downwards. Thus, the tamarins reacted as if external referents, i.e. information about the predator type or the appropriate reaction, were encoded in the acoustic features of the calls. In addition, we found no differences in the responses of S. fuscicollis and S. mystax whether the alarm call stimulus was produced by a conspecific or a heterospecific caller. Furthermore, it seems that S. fuscicollis terrestrial alarm calls were less specific than either S. mystax terrestrial predator alarms or either species’ aerial predator alarms, but because of the small sample size it is difficult to draw a final conclusion.     

Effect of alarm calling by male Red‐winged Blackbirds on nestling begging and female provisioning behavior

ABSTRACT Nestling begging and parental provisioning can attract nest predators and reduce reproductive success, so parents and their offspring might be expected to respond adaptively by minimizing predator‐attracting cues when predators threaten nests. Male Red‐winged Blackbirds (Agelaius phoeniceus) are well known for their antipredator alarm calls that contain information about the approach of potential nest predators. We examined the begging behavior of nestlings and the provisioning behavior of females in response to antipredator alarm calls of males to test the adaptive response hypothesis. Playback experiments provided no evidence that alarm calls function to switch off vocal begging; nestlings were equally likely to beg vocally during playback and control periods. Video recordings showed that male alarm calling had no significant effect on inappropriate vocal begging (in the absence of an adult), but significantly reduced the incidence of spontaneous calling (in the absence of begging). Adult females responded to male antipredator alarm calls by delaying their provisioning visits. In addition, although having no significant effect on use of nest‐arriving calls by females, male alarm calling significantly reduced their use of nest‐leaving calls. We conclude that nestling and female Red‐winged Blackbirds respond to male alarm calls in ways that might reduce the risk of predation, but nestlings beg vocally when females arrive to feed them, regardless of male alarm calling, perhaps to avoid a competitive disadvantage with broodmates.     

Age differences and developmental trends in alarm peep responses by squirrel monkeys (Saimiri sciureus)

Alarm calls can code for different classes of predators or different types of predatory threat. Acoustic information can also encode the urgency of threat through variations in acoustic features within specific alarm call types. Squirrel monkeys (Saimiri sciureus) produce an alarm call, known as the alarm peep, in highly threatening situations. Infant squirrel monkeys appear to have an innate predisposition to respond to alarm peeps but require experience to associate alarm peeps with the appropriate type of predatory threat [Herzog & Hopf, American Journal of Primatology 7:99-106, 1984]. Little is known about age-related differences in the type or frequency of response to alarm peeps, or the development of alarm peep response in infants. The purpose of this study was to test experimentally the response strategies of different age classes of squirrel monkey to the playback of alarm peeps that were produced by infants, juveniles, or adults. Results suggest that infants, juveniles, and female subadults respond more frequently to alarm peeps than do adult females. Infant squirrel monkeys showed different behavioral strategies in response to alarm peeps as a function of age. Adult females differentiate between infant and adult alarm peeps by responding more frequently to the alarm peeps of adult females. These data demonstrate that squirrel monkeys use acoustic information to discern when to respond to the alarm peeps from conspecifics, and that infants gradually develop an adult-like response to alarm peeps over the first year of development.     

Reliability and the adaptive utility of discrimination among alarm callers

Unlike individually distinctive contact calls, or calls that aid in the recognition of young by their parents, the function or functions of individually distinctive alarm calls is less obvious. We conducted three experiments to study the importance of caller reliability in explaining individual-discriminative abilities in the alarm calls of yellow-bellied marmots (Marmota flaviventris). In our first two experiments, we found that calls from less reliable individuals and calls from individuals calling from a greater simulated distance were more evocative than calls from reliable individuals or nearby callers. These results are consistent with the hypothesis that marmots assess the reliability of callers to help them decide how much time to allocate to independent vigilance. The third experiment demonstrated that the number of callers influenced responsiveness, probably because situations where more than a single caller calls, are those when there is certain to be a predator present. Taken together, the results from all three experiments demonstrate the importance of reliability in explaining individual discrimination abilities in yellow-bellied marmots. Marmots' assessment of reliability acts by influencing the time allocated to individual assessment and thus the time not allocated to other activities.     

Development in the Usage and Comprehension of Greeting Calls in a Free‐Ranging Group of Japanese Macaques (Macaca fuscata)

The main objective of this study is to clarify the developmental process involved in both the usage of greeting calls and the response to greeting calls by Japanese macaques. These greeting calls facilitate affiliative interactions by communicating benign intent. Specifically, individuals frequently emit greeting calls when interacting with less‐predictable individuals. Here, we examined whether the targets at which greeting calls are directed, along with associated behavioral responses, differed among the age classes, by conducting a cross‐sectional observation of females aged 0–5 yr and their mothers. We found that infant females showed a weak tendency to emit greeting calls at no specific receivers, unlike that by older females. Adult females emitted greeting calls more frequently when approaching unrelated females than related females. In contrast, young adult or juvenile females exhibited no significant difference in the proportion of the calls with related and unrelated conspecifics. Adult and young adult females were more likely to respond affiliatively to other individuals that approached using greeting calls compared with silent approaches, whereas juveniles did not exhibit different responses to the two types of approaches. This study showed that the target‐specific usage and affiliative response to greeting calls emerge with changes in the developmental stage. Furthermore, the fact that even young adults did not use greeting calls as adults indicates that the usage of greeting calls is modified in conjunction with the expansion of social relationships.     

No evidence of eavesdropping on heterospecific alarm calls by captive zebra finches recently descended from wild birds

Alarm calls are vocalisations animals give in response to predators which mainly function to alert conspecifics of danger. Studies show that numerous species eavesdrop on heterospecific calls to gain information about predator presence. Responding to heterospecific calls may be a learned or innate response, determined by whether the response occurs with or without prior exposure to the call. In this study, we investigated the presence of eavesdropping behaviour in zebra finches Taeniopygia guttata. This species is not known to possess a distinct alarm call to warn adult conspecifics of a threat, and could be relying on alarm calls of nearby heterospecifics for predator information. We used a playback experiment to expose captive zebra finches to three heterospecific sounds: an unfamiliar alarm call (from the chestnut‐rumped thornbill Acanthiza uropygialis), a familiar alarm call, and a familiar control (both from the noisy miner Manorina melanocephala). These calls were chosen to test if the birds had learnt to distinguish between the function of the two familiar calls, and if the acoustic properties of the unfamiliar alarm indicated presence of a threat to the finches. Our results showed that in response to the thornbill alarm, the birds reduced the rate of production of short calls. However, this decrease was also seen when considering both short and distance calls in response to the control sound. An increase in latency to call was also seen after the control stimulus when compared to the miner alarm. The time spent scanning increased in response to all three stimuli, but this did not differ between stimuli. There were no significant differences when considering the stimulus by time interaction for any of the three vigilance measures. Overall, no strong evidence was found to indicate that the captive zebra finches were responding to the heterospecific alarm stimuli with anti‐predator behaviour.     

A ‘crying wolf’ game of interspecific kleptoparasitic mutualism

We model a potentially mutualistic interaction between a species making antipredator alarm calls and a species which eavesdrops on those calls. Callers may or may not make deceptive alarm calls in order to kleptoparasitize food from eavesdroppers, which in turn may either heed or ignore all alarm calls. The two most likely outcomes in our model are either maximally deceptive callers and maximally trusting eavesdroppers, or persistently cycling strategy frequencies. The latter is favoured by low predator density, low density of any alternative honest alarm-calling species, ability of eavesdroppers to preferentially heed calls when costs of doing so are low and, in some cases, low food availability.     

The information that receivers extract from alarm calls in suricates.

Field observations and acoustic analyses have shown that suricate (Suricata suricatta) alarm calls vary in their acoustic structure depending on predator type. In this study, we tested whether receivers respond appropriately when hearing a call in the absence of a predator. Although the only way for suricates to escape from predators is to retreat to boltholes, responses to playbacks could be divided into distinct categories. The subjects responded differently to alarm calls given in response to aerial or terrestrial predators and to recruitment calls emitted in response to snakes and deposits on the ground. Suricates also showed rather distinct responses to low, medium and high urgency aerial calls. Differences in the responses were less obvious for different levels of urgency in the terrestrial and recruitment calls. Suricate receivers thus gain information about both the predator type and level of urgency from the acoustic structures of their calls.     

Dual Function of Chip Calls Depending on Changing Call Rate Related to Risk Level in Territorial Pairs of White‐Eared Ground‐Sparrows

Different mechanisms have been proposed for encoding information into vocalizations: variation of frequency or temporal characteristics, variation in the rate of vocalization production, and use of different vocalization types. We analyze the effect of rate variation on the dual function of chip calls (contact and alarm) produced by White‐eared Ground‐sparrows (Melozone leucotis). We conducted an acoustic playback experiment where we played back 1 min of four chip call rates (12, 36, 60, 84 calls/min). We measured the response of territorial pairs using behavioral responses, and fine structural features of calls produced in response to those playbacks. White‐eared Ground‐sparrows showed more intense behavioral responses to higher than lower call rate playbacks. Both individuals of the pair approached the source of the playback stimulus faster, produced the first vocalization faster, produced more vocalizations, and spent more time close to the stimulus in higher call rate than in lower call rate playbacks. Frequency and duration characteristics of calls (chip and tseet) were similar in response to all call rate playbacks. Our playback experiment elicited different intensity of behavioral responses, suggesting that risk‐based information is encoded in call rate. Our results suggest that variation in the rate of chip call production serves a dual function in this species; calls are used at lower rates for pair contact and at higher rates for alarm/mobbing signals.     

Variation in and Meaning of Alarm Calls in a Social Desert Rodent Rhombomys opimus

The great gerbil (Rhombomys opimus), a social rodent that lives in family groups, emits three different alarm vocalizations in the presence of predators: a rhythmic call; a faster more intense call; and a single whistle. We tested the hypothesis that the alarm calls communicate risk of predation. We quantified the relationship between predator distance and type of alarm call via human approaches to gerbils. We also tested responses of focal adults in family groups to playback broadcasts of the different calls and controls of bird song and tape noise. Results showed that alarm calls were related to distance from a predator. Gerbils gave the rhythmic call when the predator was farthest away, the more intense call as the predator moved closer; and a short whistle when startled by a close approach of the predator. Gerbils stopped feeding and stood vigilant in a frozen alert posture in response to playbacks of all three alarm calls. They decreased non‐vigilant behavior to the alarm vocalizations more than to the controls and decreased non‐vigilant behavior significantly more in response to the intense alarm and whistle compared with the rhythmic alarm. We conclude that one function of gerbil alarm calls is to communicate response urgency to family members. The rhythmic alarm communicates danger at a distance, whereas the intense alarm and whistle signal the close approach of a predator.     

Individual and Contextual Variation in Thomas Langur Male Loud Calls

Individual and contextual differences in male loud calls of wild Thomas langurs (Presbytis thomasi) were studied in northern Sumatra, Indonesia. Loud calls were given in the following contexts: morning calls, vocal responses to other groups, between‐group encounter calls and alarm calls. Loud call spectrograms were analysed for a large number of variables. With discriminant analyses, 14 variables were found to be important in distinguishing individuals and contexts. Loud calls were assigned to the correct individual in 95.6% of the cases (91.8% with ‘leave‐one‐out’ validation) and to the correct context in 52.2% of the cases (39.0% with ‘leave‐one‐out’ validation). Further analyses with two‐way anova s showed significant differences in both temporal and frequency variables between individuals and contexts. Loud calls seemed to differ between the contexts in functionally meaningful ways, relating to the distance of the intended receivers and to the urgency of the message. Observation showed that females in the caller's group collected infants more often in the between‐group encounter context and in the alarm call context than in the vocal exchange context. These differential responses suggest that the monkeys also perceive the measurable differences in loud call characteristics between the various contexts.     

Does Gray Squirrel (Sciurus carolinensis) Response to Heterospecific Alarm Calls Depend on Familiarity or Acoustic Similarity?

In habitats in which multiple species are prey to the same predators, individuals can greatly benefit from recognizing information regarding predators that is provided by other species. Past studies have demonstrated that various mammals respond to familiar heterospecific alarm calls, but whether acoustic similarity to a familiar call can prompt a mammal's recognition of an unfamiliar call has yet to be shown. We presented alarm calls to free‐ranging eastern gray squirrels (Sciurus carolinensis) and recorded behavioral changes in vigilance and antipredatory response. Playbacks included alarm calls of a sympatric bird (American robin, Turdus migratorius), an allopatric bird with a call structure similar to that of the robin (common blackbird, Turdus merula), and an allopatric bird with a distinct call structure (New Holland honeyeater, Phylidonyris novaehollandiae). Squirrels responded significantly more frequently to squirrel alarm calls (positive control) than to robin song (negative control) or honeyeater calls. Squirrel response to robin and blackbird alarm calls was statistically similar to their response to squirrel alarm calls, indicating that squirrels responded to those alarm calls as if they provided information about the presence of predators. However, squirrel response to robin song was not statistically different from response to any of the other avian calls, including the robin and blackbird alarms, suggesting that squirrels neither respond to blackbird alarms as if they clearly signify danger, nor as if they clearly do not signify danger, perhaps reflecting some ambiguity in interpretation of the calls. These results suggest that squirrel responses to alarm calls are generally based on call familiarity, but that acoustic similarity of an unfamiliar allopatric call to a familiar call also can elicit antipredator behavior. The lack of response to honeyeater alarm calls also supports the hypothesis that call recognition by gray squirrels is dependent on familiarity, rather than simply detection of an acoustic feature common to alarm calls across a variety of avian species.     

On the Meaning of Alarm Calls: A Review of Functional Reference in Avian Alarm Calling

A long‐standing question in animal communication is whether signals reveal intrinsic properties of the signaller or extrinsic properties of its environment. Alarm calls, one of the most conspicuous components of antipredator behaviour, intuitively would appear to reflect internal states of the signaller. Pioneering research in primates and fowl, however, demonstrated that signallers may produce unique alarm calls during encounters with different types of predators, suggesting that signallers through selective production of alarm calls provide to conspecific receivers information about predators in the environment. In this article, we review evidence for such ‘functional reference’ in the alarm calls of birds based on explicit tests of two criteria proposed in Macedonia & Evans’ (Ethology 93, 1993, 177) influential conceptual framework: (1) that unique alarm calls are given to specific predator categories, and (2) that alarm calls isolated from contextual information elicit antipredator responses from receivers similar to those produced during actual predator encounters. Despite the importance of research on birds in development of the conceptual framework and the ubiquity of alarm calls in birds, evidence for functionally referential alarm calls in this clade is limited to six species. In these species, alarm calls are associated with the type of predator encountered as well as variation in hunting behaviour; with defence of reproductive effort in addition to predators of adults; with age‐related changes in predation risk; and with strong fitness benefits. Our review likely underestimates the occurrence of functional reference in avian alarm calls, as incomplete application and testing of the conceptual framework has limited our understanding. Throughout, therefore, we suggest avian taxa for future studies, as well as additional questions and experimental approaches that would strengthen our understanding of the meaning of functional reference in avian alarm calls.     

Alarm call‐based discrimination between common cuckoo and Eurasian sparrowhawk in a Chinese population of great tits

Morphological resemblance of the common cuckoo Cuculus canorus to the Eurasian sparrowhawk Accipiter nisus has been regarded as an example of predator mimicry. Common hosts could distinguish parasites as the result of coevolution, while rare hosts or non‐hosts may mistake cuckoos for hawks because rare hosts or non‐hosts behave similarly when faced with these two species. Birds usually produce alarm calls in addition to showing behavioral responses when in danger. However, previous studies of identification by rare hosts or non‐hosts of sparrowhawks usually lacked experimental evidence of alarm calls. Great tits Parus major, a rare cuckoo host, perform similar behaviors and usually produce alarm calls in response to sparrowhawks and common cuckoos. Here, we tested whether great tits could distinguish common cuckoo from sparrowhawk based on analysis of their alarm calls and the effects of playback of alarm calls on conspecific behavior. Previous studies showed that great tits have a complex communication system that conveys information about predators, and they could perform different kinds of response behavior to different alarm calls. If great tits have not made the ability to distinguish between common cuckoo and sparrowhawk, then their acoustic responses to these two species and their response behaviors in playback experiments should be similar. Specimens of a common cuckoo (parasite), a sparrowhawk (predator) and an Oriental turtle dove Streptopelia orientalis (harmless control) were used to elicit and subsequently record the response behavior and alarm calls of great tits. There was no significant difference in behavioral response among great tits when exposed to the dummy of cuckoo, sparrowhawk and dove. In contrast, they differed significantly in alarm calls. Great tits produced more notes per call that contained increasing D‐type and decreasing I‐type notes when responding to sparrowhawk as compared to cuckoo or dove. In playback experiments, we found that great tits responded more strongly to great tit hawk than to great tit cuckoo or great tit dove alarm calls. Our study suggests that great tits are able to distinguish sparrowhawks from common cuckoos and convey relevant information in alarm calls by adjusting the number and combinations of notes of a single call type.