Testing social learning of anti-predator responses in juvenile jackdaws: the importance of accounting for levels of agitation

Abstract

Social learning is often assumed to help young animals respond appropriately to potential threats in the environment. We brought wild, juvenile jackdaws briefly into captivity to test whether short exposures to conspecific vocalizations are sufficient to promote anti-predator learning. Individuals were presented with one of two models—a stuffed fox representing a genuine threat, or a toy elephant simulating a novel predator. Following an initial baseline presentation, juveniles were trained by pairing models with either adult mobbing calls, indicating danger, or contact calls suggesting no danger. In a final test phase with no playbacks, birds appeared to have habituated to the elephant, regardless of training, but responses to the fox remained high throughout, suggesting juveniles already recognized it as a predator before the experiment began. Training with mobbing calls did seem to generate elevated escape responses, but this was likely to be a carry-over effect of the playback in the previous trial. Overall, we found little evidence for social learning. Instead, individuals' responses were mainly driven by their level of agitation immediately preceding each presentation. These results highlight the importance of accounting for agitation in studies of anti-predator learning, and whenever animals are held in captivity for short periods.

Asymmetrical interspecific communication of predatory threat in mixed‐species colonies of lesser kestrels (Falco naumanni) and jackdaws (Corvus monedula)

“…The diminished defensive behaviour of lesser kestrels inhabiting mixed‐species colonies with jackdaws relative to those in single‐species colonies without co‐nesting jackdaws (Campobello et al, ) may thus, at least in part, be explained by the potential reliance of lesser kestrels on jackdaw harsh calls communicating the presence of threat. Beyond increased vigilance, the tendency of jackdaws and lesser kestrels in the present study to increase the production of alarm calls in response to detecting a jackdaw harsh call further suggests contagious amplification of alarm when a threat is detected (Snow & Snow, ; Venci, ), benefitting conspecifics and heterospecifics alike, consistent with “harsh” calls serving as antipredator mobbing calls (“scolding calls” sensu McIvor et al, ; Woods et al, ). This contagion may also explain the enhanced vigilance of jackdaws and lesser kestrels to jackdaw magpie‐elicited calls, which, like jackdaw harsh calls, proved more salient in eliciting alarm responses than calls emitted in the presence of non‐predator models.…”

“…Numerical codes were assigned to each selected call, blinding the coder to the model type associated with the calls being parameterized. For each selected JD “kaar” call (Röell, ), JD “harsh” call (also referred to as a “scolding” call; McIvor, Lee, & Thornton, ; Woods, Kings, McIvor, & Thornton, ) or LK “kee‐chee‐chee” call (Cramp, ), we used Avisoft‐SASLabPro V4.4 software (Avisoft Bioacoustics) to visualize and parameterize the spectral properties of the recorded vocalizations. These recordings subsequently served as the high‐quality playback exemplars for the call response phase of our study, where we tested for differential response of LKs and JDs to the playback of recorded vocalizations alone (see below).…”

Wild jackdaws are wary of objects that violate expectations of animacy

“…Birds' nest-box entrance time was also noted, and if they did not enter within 20 min of the trigger, they were assigned a maximum entrance time of 1200 s. Prior research with jackdaws indicates that latency to approach and enter a nest-box can be used as a threat response measure [ 24 , 30 ]. The total number of scolding calls (a defensive alarm call used to recruit others and drive away potential threats [ 31 , 32 ]) made from the time of the trigger to the end of the trial was recorded to determine if jackdaws attempted to defend their nest when the stimulus was presented. Inter-coder reliability was assessed with a one way intraclass correlation coefficient [ 33 ] and was extremely high (ICC (1) = 0.96, CI = 0.91–0.98, p < 0.001).…”

Caller characteristics influence recruitment to collective anti-predator events in jackdaws

“…Jackdaws breed colonially, live in structured groups with a defined linear rank hierarchy and form long-term monogamous pair bonds 17 , 18 . In response to threats, they produce a harsh, rattling, “scolding” call 19 , which typically serves to recruit other group members the caller’s location. Recruits may further respond with their own scolding calls, and if a predator is present the group may mob it aggressively 17 , 20 .…”