Alarm Calls of the Australian Magpie (Gymnorhina tibicen): Predators Elicit Complex Vocal Responses and Mobbing Behaviour

Abstract

Mobbing calls are produced by many avian species as part of a defence strategy against predators. However, as most studies have described small prey species, little is known of mobbing by species large enough to inflict harm on the predator when working cooperatively. We investigated the mobbing calls of the Australian magpie (Gymnorhina tibicen tibicen), a large, territorial songbird known to be exceptionally vigilant and to attack predators. We were particularly interested in this species because it has a very large vocal repertoire. Magpie groups (N=45) in semi-rural and rural localities were presented with taxidermic specimens of three predators, two species of eagle and a monitor lizard, the latter known to be a risk to their eggs and nestlings. We identified five distinct types of alarm calls, one of which (a complex, tonal call of more than two syllables) was elicited almost exclusively by the eagles in environments where they are known to be a threat to magpies. This alarm call usually preceded intense swooping attacks of the eagle models and often continued during the attacks. A harsh and noisy call of one syllable was the most frequently produced call and appeared to indicate level of arousal. The lizard did not elicit the multi-syllable call or any swooping attacks but it did elicit the harsh call. Some other call types showed less stimulus specificity although a two-syllable call was elicited more commonly by the eagles than lizard. Hence, this species has an acoustically complex, multi-syllable alarm call to signal the presence of an aerial predator in contexts of genuine threat, and this call is markedly different from the harsh single-syllable call, which indicates arousal level and is used most frequently when mobbing a monitor lizard.

Audition and Hemispheric Specialization in Songbirds and New Evidence from Australian Magpies

“…Field studies playing back alarm calls established that at least one of these calls is a referential alarm call, signalling the presence of an eagle [95]. We then also established the stability of such referentiality in different magpie subspecies and very different locations [96].…”

“…Learned vocalizations in song, while not tutored, may have elements that are territorial or regional markers, and all mimicry is of course learned. Intentional vocalizations can be long or short, but they must have stereotyped characteristics, be uttered only in the presence of conspecifics and would usually lead to a change of behaviour in others (see [93,95]). …”

Stability of referential signalling across time and locations: testing alarm calls of Australian magpies (Gymnorhina tibicen) in urban and rural Australia and in Fiji

“…1A) and, because of a series of minibreaths and variations in membrane activation of the syrinx (Suthers, Wild & Kaplan, 2011) can be performed for hours. The magpie’s repertoire also includes many alarm calls that we described and classified previously (Kaplan et al, 2009). They range from a monosyllabic, harsh call that appears to signal the bird’s state of arousal to very complex and tonally distinct calls, produced when a raptor is seen in contexts in which such predators are a serious threat to adult birds (Kaplan et al, 2009).…”

“…They range from a monosyllabic, harsh call that appears to signal the bird’s state of arousal to very complex and tonally distinct calls, produced when a raptor is seen in contexts in which such predators are a serious threat to adult birds (Kaplan et al, 2009). We had elicited these calls by presenting taxidermic models of raptors to a large number of magpie groups in rural and urban settings (Kaplan et al, 2009) and, as an extension of this research, can now present evidence of their function and use in entirely different locations, two in which magpies are native birds and abundant (inland New South Wales), and a third to which they had been introduced from New South Wales to a Pacific island.…”

Mechanisms of song production in the Australian magpie

“…The latter include a complex set of short alarm calls of enormous variety—some 27 variations have been identified falling into 5 distinct classes (Kaplan 2008a; Kaplan et al 2009)—and territorial vocalizations referred to as carols or warble carols. Brown and Farabaugh (1991) identified 204 carol and warble–carol syllable types belonging to 11 general classes in a population of 24 magpies.…”