Congdonetal2016 Predator&ConspecificCalls IJCP (original) (raw)
A songbird mimics different heterospecific alarm calls in response to different types of threat
Behavioral Ecology, 2014
Birds frequently mimic other species' alarm calls, but the type of information conveyed to receivers, and therefore the function of mimetic alarm calls, is often unknown. Alarm calls can convey predator-specific information that influences how receivers respond: aerial alarms signal the presence of flying predators and provoke receivers to flee, whereas mobbing alarm calls signal the presence of less dangerous predators and provoke receivers to mob. The function of mimetic alarm calls may therefore depend on the type of heterospecific alarm calls mimicked. We examined the use of alarm call mimicry by brown thornbills (Acanthiza pusilla) across different contexts of danger: terrestrial threat, aerial threat, when captured by a predator and during nest attack. Thornbills were most likely to include mimetic alarm calls among their vocalizations when captured and during nest attack, less likely in response to terrestrial and aerial predator threats, and least likely in the absence of any threat. Furthermore, the type of danger affected the type of mimetic alarm calls used: thornbills mimicked mobbing alarm calls in response to terrestrial threat and aerial alarm calls in response to aerial threat but also during capture and nest attack where no aerial danger was present. We suggest that mimicking predator-appropriate heterospecific alarm calls in response to aerial and terrestrial threats may facilitate interspecific alarm communication with other prey species, whereas mimicking heterospecific aerial alarm calls in the absence of aerial predators might deceptively startle predators to release captured callers or offspring when attacked.
Alarming features: birds use specific acoustic properties to identify heterospecific alarm calls
Vertebrates that eavesdrop on heterospecific alarm calls must distinguish alarms from sounds that can safely be ignored, but the mechanisms for identifying heterospecific alarm calls are poorly understood. While vertebrates learn to identify heterospecific alarms through experience, some can also respond to unfamiliar alarm calls that are acoustically similar to conspecific alarm calls. We used synthetic calls to test the role of specific acoustic properties in alarm call identification by superb fairy-wrens, Malurus cyaneus. Individuals fled more often in response to synthetic calls with peak frequencies closer to those of conspecific calls, even if other acoustic features were dissimilar to that of fairy-wren calls. Further, they then spent more time in cover following calls that had both peak frequencies and frequency modulation rates closer to natural fairy-wren means. Thus, fairy-wrens use similarity in specific acoustic properties to identify alarms and adjust a two-stage antipredator response. Our study reveals how birds respond to heterospecific alarm calls without experience, and, together with previous work using playback of natural calls, shows that both acoustic similarity and learning are important for interspecific eavesdropping. More generally, this study reconciles contrasting views on the importance of alarm signal structure and learning in recognition of heterospecific alarms.
Communicating about danger: urgency alarm calling in a bird
Animal Behaviour, 2005
Vertebrate flee alarm calls can provide information about the type of predator, and some mammalian alarm calls also appear to communicate the degree of danger and therefore urgency of escape. However, because predators are usually rare, it has proved difficult to obtain observations differing only in the degree of danger, or to record sufficient naturally provoked alarm calls for fully replicated playback experiments. In this study, we took advantage of a system in which the major aerial predator was common, allowing repeated, matched observations of natural interactions between predator and prey, combined with a fully replicated playback experiment. We found that the aerial trill alarm call of the white-browed scrubwren, Sericornis frontalis, varied according to the distance from the suddenly appearing predator: the closer the predator, the greater the number of elements in the call and the higher their minimum frequency (pitch). Playback experiments showed that multi-element alarm calls prompted a more urgent response, including immediate fleeing to cover. Furthermore, the response was graded, such that an alarm with more elements provoked a more urgent response. Our study therefore isolated the effect of predator distance on alarm call design, and showed that individuals respond appropriately to calls in the absence of any other cues. To our knowledge, this is the most explicit demonstration that avian flee alarm calls can convey urgency.
Mechanisms of heterospecific recognition in avian mobbing calls
Australian Journal of Zoology, 2003
Some birds emit special calls, referred to as mobbing calls, when they detect a predator in their area. These calls are easily localisable and function to rally other individuals to help chase out a threatening intruder. Interestingly, individuals may respond to the mobbing calls of other sympatric species. To understand the mechanism underlying interspecific recognition it is essential to determine whether birds also respond to the mobbing calls of allopatric species. If, as has been suggested, learning is important for call recognition, then calls from allopatric species should not evoke mobbing. If, however, there are intrinsic (and possibly convergent) characteristics of mobbing calls, then novel calls from allopatric species should evoke mobbing. We conducted two playback experiments with apostlebirds (Struthidea cinera, Family Corcoracidae), Australian mud-nesters, to understand mechanisms underlying mobbing-call recognition. The first demonstrated that allopatric mobbing call...
On the Meaning of Alarm Calls: A Review of Functional Reference in Avian Alarm Calling
Ethology, 2013
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.
Recognition of other species' aerial alarm calls: speaking the same language or learning another?
… of the Royal …, 2009
Alarm calls given by other species potentially provide a network of information about danger, but little is known about the role of acoustic similarity compared with learning in recognition of heterospecific calls. In particular, the aerial 'hawk' alarm calls of passerines provide a textbook example of signal design because many species have converged on a design that thwarts eavesdropping by hawks, and call similarity might therefore allow recognition. We measured the response of fairy-wrens (Malurus cyaneus) to playback of acoustically similar scrubwren (Sericornis frontalis) aerial alarm calls. First, if call similarity prompts escape independent of learning, then fairy-wrens should flee to playback of scrubwren calls outside their geographical range. However, fairy-wrens fled only in sympatry. Second, if call similarity is necessary for learning heterospecific calls, then fairy-wrens should not respond to sympatric species with different calls. We found, on the contrary, that fairy-wrens fled to the very different aerial alarm calls of a honeyeater (Phylidonyris novaehollandiae). Furthermore, response to the honeyeater depended on the specific structure of the call, not acoustic similarity. Overall, call similarity was neither sufficient nor necessary for interspecific recognition, implying learning is essential in the complex task of sifting the acoustic world for cues about danger.
Behavioral Ecology and Sociobiology, 2012
Chick-a-dee calls function in social organization in Poecile (chickadee) species. Recent field and aviary studies have found that variation in chick-a-dee calls relates to the type or proximity of avian predator, or level of threat. Earlier studies on calls in the context of predator stimuli have typically used stationary and perched predator models. For chickadees and other small songbirds, more frequently detected and more dangerous avian predatory stimuli are flying predators. In the present study, we tested whether simulated flying avian predator and control models influenced chick-a-dee calling behavior of wild Carolina chickadees, Poecile carolinensis. At 20 independent field sites, chickadee subjects were presented with wooden models that were painted to resemble either a predatory sharp-shinned hawk (Accipiter striatus) or a blue jay (Cyanocitta cristata) and that were made to "fly" down a zip line near a feeding station chickadees were using. The note composition of chick-a-dee calls was affected by both the flight of stimuli and type of model. Call variation in this flying predator context suggests interesting similarities and differences with experimental findings with congeners. Finally, increased production of certain notes to the flying of both model types provides support for a "Better Safe than Sorry" strategy. When costs of alarm calling are low but costs of discriminating potentially serious threats may be extremely high, individuals should err on the side of caution, and alarm call to any potentially threatening stimulus.
Vivid birds respond more to acoustic signals of predators
Behavioral Ecology and Sociobiology, 2013
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".