Steller’s jays assess and communicate about predator risk using detection cues and identity

Nuthatches vary their alarm calls based upon the source of the eavesdropped signals

“…Information coded in graded vocalizations, such as nuthatch and chickadee mobbing vocalizations, is often thought to be simply a reflection of the behavioural state of arousal of the calling bird 1 , or level of risk 15 . Our findings, in conjunction with those of Templeton and Greene 24 and Billings et al 55 , suggest that this may not always be the case. Templeton and Greene 24 showed that nuthatches varied their anti-predator behaviour when they heard chickadee mobbing calls signifying different threat levels-implying heightened stress/arousal levels-while the current study demonstrates that these nuthatch behaviours do not necessarily translate to variation in their own vocalizations.…”

“…For example, bird species that are more prevalent in the diet of a Eurasian pygmyowl (Glaucidum passerinum) are more likely to mob that predator 74 . Additionally, heterospecifics, even allopatric species from the same family 5 , may use different ways to encode predator threat information in their alarm calls 55 ; and while some species can learn to recognize heterospecific calls either by associating a new call with their own alarm calls or by associating a new call with the presence of a predator, as superb fairy-wrens (Malurus cyaneus) do 32,33 , not all species may be able to learn these associations.…”

“…looking up in response to aerial predator calls, and down in response to 'terrestrial' predator calls 16 ), chickadee calls are likely not correlated directly with the threat itself but rather a measure of a particular chickadee's perceived threat level. It is likely that features other than predator species could impact a chickadee's overall threat assessment, including the predator's behaviour or distance, the presence of other conspecifics, or the calling individual's age, sex, experience, personality type, general stress level, internal state, or distance from protective cover 23,[47][48][49][50][51][52]54,55,[74][75][76][77][78] . Thus, individuals should be strategic in how they use different types of information 44,45,[71][72][73] .…”

“…public or indirect information) could sometimes provide an inaccurate representation of the threat [44][45][46][47] . A number of factors, for example life history features of a given species 43,[48][49][50][51][52][53][54] , or predator detection 55 could affect how individuals assess or respond to different threats; because the information included in these calls are thought to be a representation of the caller's perceived threat, not the threat itself 45 , the reliability or accuracy of these calls to heterospecifics (and sometimes conspecifics) is potentially limited 45,53,56 . Although studies of alarm calls have provide a rich window on animal perception and behaviour, we still have important and outstanding questions about whether and how animals encode threat levels about predators depending on the source of the information-direct, personal information (e.g.…”

Top‐down limitation of mesopredators by avian top predators: a call for research on cascading effects at the community and ecosystem scale

“…Similar experimental manipulations using visual (e.g. taxidermied raptors with small servo motors to move their heads, see Billings et al 2017) or acoustic (call playbacks) cues of different large raptor species (Billings et al 2017) would make it possible to determine whether mesopredators (mammalian mesopredators and corvids) alter their foraging behaviour in the presence of avian top predators, show reduced foraging time and success, or change habitat use and how this reverberates throughout food webs in diverse ecosystems varying in their level of anthropization.…”