Contagious risk taking: social information and context influence wild jackdaws' responses to novelty and risk.

Although wild animals increasingly encounter human-produced food and objects, it is unknown how they learn to discriminate beneficial from dangerous novelty. Since social learning allows animals to capitalize on the risk-taking of others, and avoid endangering themselves, social learning should be used around novel and unpredictable stimuli. However, it is unclear whether animals use social cues equally around all types of novelty and at all times of year. We assessed whether wild, individually marked jackdaws-a highly neophobic, yet adaptable species-are equally influenced by social cues to consume novel, palatable foods and to approach a startling object. We conducted these tests across two seasons, and found that in both seasons observers were more likely to consume novel foods after seeing a demonstrator do so. In contrast, observers only followed the demonstrator in foraging next to the object during breeding season. Throughout the year more birds were wary of consuming novel foods than wary of approaching the object, potentially leading to jackdaws' greater reliance on social information about food. Jackdaws' dynamic social cue usage demonstrates the importance of context in predicting how social information is used around novelty, and potentially indicates the conditions that facilitate animals' adjustment to anthropogenic disturbance.A.L.G. is supported by the generosity of the Gates-Cambridge Trust. A.T. was supported by a BBSRC David Phillips Fellowship (BB/H021817/1).This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/srep2776

Crows' nests on power poles : finding a solution

Crows (Corvus cornix and C. corone) nest on power-poles throughout northern Scotland causing interruptions to electricity that cost the electricity provider more than £250,000 annually. I aimed to establish what factors influence the nest site selection of crows in the islands of Orkney to help determine ways to reduce pole nesting by these birds. Crows preferred nest sites in trees that were coniferous, tall, mature, densely grouped, and far from occupied houses. However, when such trees were scarce, the number of occupied houses was high, and there were no cliffs within 1km, crows were more likely to nest on power-poles. I found that the fitting of a Firefly diverter at sites where nests were removed was ineffective at deterring rebuilding, but rebuilding was less likely to occur the later in the season that nests were removed. Nests in the middle phase of construction were the most likely to be rebuilt. Making an appropriate decision as to when to remove a crow nest, therefore, would seem more effective for deterring nest rebuilding than is the fitting of Firefly diverters. Nest removal also reduced the level of pole nesting both within years and between years. Furthermore, planned interruptions led to fewer customers losing power and to a twelve-fold reduction in the number of minutes that customers were without power, relative to unplanned power-cuts caused by nests. I also attempted to determine the efficacy of providing alternative nesting platforms and of insulating the live wires on transformer boxes, but I collected too few data to confirm if either of these might reduce the number of power-cuts caused by crows' nests. As both nest platforms and insulation remain in place, however, data collected from these sites in the future may allow confirmation (or not) as to their value

Nest site selection and patterns of nest re-use in the Hooded Crow <i>Corvus cornix</i>

Capsule: Hooded Crows Corvus cornix selected nesting trees based on species, height, grouping and distance from an occupied house. Nest re-use was common and pairs that re-used old nests produced more fledglings than those that built a new nest.Aims: To determine the features of trees that influenced whether they were used by Hooded Crows as nest sites, to establish what factors influenced nest re-use between years and to explore potential costs or benefits of nest re-use.Methods: In a large area of Orkney, Scotland, the features of trees that contained a Hooded Crow nest were compared to those of trees where nests were absent. Patterns of nest re-use between years were examined in relation to the availability of alternative sites, previous nesting success and the number of equivalent options to the tree used previously within 200 m of this site.Results: Hooded Crows favoured spruce and pine trees as nest sites, above the most locally abundant tree species, elder and willow. Preference for trees increased with tree height, local tree density and distance from occupied houses. Over half of the crows studied re-used an old nest when one was available and crows that re-used an old nest fledged more offspring than those that built a new nest. The likelihood of a new nest being built increased as the number of potential locations to build increased. Territories where a nest survived the winter were more likely to be reoccupied the following year than those where nests fell, while territories with fewer trees around the old site were most likely to be abandoned, suggesting that those were territories of lower quality.Conclusions: Hooded Crows displayed strong preferences for nest sites that might favour nesting success by offering concealment, shelter and protection from ground-based predators. Nest re-use was common, especially when alternative sites were scarce, and appeared to facilitate greater reproductive output

Nest site selection and patterns of nest re-use in the Hooded Crow <i>Corvus cornix</i>

Capsule: Hooded Crows Corvus cornix selected nesting trees based on species, height, grouping and distance from an occupied house. Nest re-use was common and pairs that re-used old nests produced more fledglings than those that built a new nest.Aims: To determine the features of trees that influenced whether they were used by Hooded Crows as nest sites, to establish what factors influenced nest re-use between years and to explore potential costs or benefits of nest re-use.Methods: In a large area of Orkney, Scotland, the features of trees that contained a Hooded Crow nest were compared to those of trees where nests were absent. Patterns of nest re-use between years were examined in relation to the availability of alternative sites, previous nesting success and the number of equivalent options to the tree used previously within 200 m of this site.Results: Hooded Crows favoured spruce and pine trees as nest sites, above the most locally abundant tree species, elder and willow. Preference for trees increased with tree height, local tree density and distance from occupied houses. Over half of the crows studied re-used an old nest when one was available and crows that re-used an old nest fledged more offspring than those that built a new nest. The likelihood of a new nest being built increased as the number of potential locations to build increased. Territories where a nest survived the winter were more likely to be reoccupied the following year than those where nests fell, while territories with fewer trees around the old site were most likely to be abandoned, suggesting that those were territories of lower quality.Conclusions: Hooded Crows displayed strong preferences for nest sites that might favour nesting success by offering concealment, shelter and protection from ground-based predators. Nest re-use was common, especially when alternative sites were scarce, and appeared to facilitate greater reproductive output

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

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 vocalisations 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 recognised 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

Data from: Evidence for individual discrimination and numerical assessment in collective antipredator behaviour in wild jackdaws (Corvus monedula)

Collective responses to threats occur throughout the animal kingdom but little is known about the cognitive processes underpinning them. Antipredator mobbing is one such response. Approaching a predator may be highly risky, but the individual risk declines and the likelihood of repelling the predator increases in larger mobbing groups. The ability to appraise the number of conspecifics involved in a mobbing event could therefore facilitate strategic decisions about whether to join. Mobs are commonly initiated by recruitment calls, which may provide valuable information to guide decision-making. We tested whether the number of wild jackdaws responding to recruitment calls was influenced by the number of callers. As predicted, playbacks simulating three or five callers tended to recruit more individuals than playbacks of one caller. Recruitment also substantially increased if recruits themselves produced calls. These results suggest that jackdaws use individual vocal discrimination to assess the number of conspecifics involved in initiating mobbing events, and use this information to guide their responses. Our results show support for the use of numerical assessment in antipredator mobbing responses and highlight the need for a greater understanding of the cognitive processes involved in collective behaviour

Recruits to scold call playbacks (main dataset)

This file includes the number of jackdaws recruited to playbacks of one, three and five individuals calling. It is the main dataset for analysis. Also included is the README text file for all the datafiles associated with the paper

MCMCglmm_dataset.GEM

The file is the csv for the MCMCglmm analysis which looked at if any one individual was particularly influential in the playbacks. All the information from the main dataset is included as well as the additional columns which state for each playback which individuals were included in the playback track

R code for analysis of all data associated with number of recruits to jackdaw playbacks

This file is the R code for all the analysis associated with the paper on number of individuals recruited to playbacks of one, three and five callers. It includes model checks, the IT approach to model selection (dredge), overdispersion checks and tests with the responsive scolding playbacks excluded. It also includes post hoc analysis on playbacks without repeat calls, tests between GS3 and GS5 and the MCMCglmm analysis for looking at influence of individual callers

2019.Withoutrepeatcalling

Subset of data without playback tracks that had repeated calls in them. For supplementary analysi