Perisoreus Infaustus Research Articles

The Use of the Microstructure of Coverling Feathers in the Systematics of Ground Jays (Aves, Corvidae: <i>Podoces, Eupodoces</i>)

Using scanning electron microscopy, new data on the microstructure of the definitive coverling feathers of all four species of ground jays Podoces pleskei, P. panderi, Eupodoces hendersoni and E. biddulphi and eight other species of Corvidae were obtained: Ptilostomus afer, Garrulus glandarius, Perisoreus infaustus, Corvus cornix, Cyanopica cyana, Nucifraga caryocatactes, Pica pica and Pyrrhocorax pyrrhocorax. Comparative morphological analysis involving previously published data on the microstructure of the pen-feathers of these species, as well as Corvus monedula, C. frugilegus, C. corax, revealed a number of feather microstructures specific to ground jay species, as well as differences between Podoces and Eupodoces, which confirms their genus status, possible relationship with G. glandarius and Pt. afer, as well as the preservation of ancestral features in P. pleskei.

A Sacred Tree in the Boreal forest: A Narrative About a Sámi Shaman, her Tree, and the Forest Landscape

Since the early nineteenth century, forest landscapes and socio-economic contexts have significantly changed in northernmost Sweden. These processes include agrarian colonisation, the Christianisation of the indigenous Sámi people, and the transfer of land tenure. We aim to analyse how Sámi religious practice manifested itself in a time of dramatic social transition in northern Sweden by focussing on the life and religious practice of a Sámi woman known as the shaman Guoksik-gummo, 'the Lady of the Siberian Jay.' We analyse a range of historical records and one specific sacred tree related to her to understand this period better and illuminate the changes in land-use religious practice and landscape transformation between the early nineteenth century and the early twenty-first century. We conclude that better documentation, more vital protection by law of Sámi cultural traces in northern landscapes, and better consultation with Sámi are needed in the future.

Rozważania nad genezą dwóch rosyjskich ornitonimów (ros. кукша oraz ронжа ‘sójka syberyjska’)

The article discusses two Russian terms for ‘Siberian jay’, кукша and ронжа, which seem to be foreign borrowings. The Siberian jay (Perisoreus infaustus L.) is a small bird belonging to the family Corvidae with a widespread distribution in the coniferous forests of Northern Eurasia. It can be suggested that the Russians borrowed both ornithonyms from Finno-Ugric tribes, who much earlier settled in Eastern Europe. The Russian noun кукша could be borrowed not only from the Permian language (cf. Zyrian kukša ‘Siberian jay’), but also from a Balto-Finnic language (e.g. Karelian kuukšo ‘id.’). There is no doubt that these Finno-Ugric nouns go back to Uralic *kokśi ‘Siberian jay (or spotted nutcracker)’, with close cognates in the Samoyed languages (cf. ProtoSamoyed *käsə̑rä ‘spotted nutcracker, Nucifraga caryocatactes L.’). The origin of Russ. ронжа. dial. роньжа f. ‘Siberian jay’ is less transparent. Most researchers assume a borrowing from a Baltic source. Ornithonyms recorded in the East Baltic languages (e.g. Lithuanian rą́šis, Latvian ruozis ‘spotted nutcracker, Nucifraga caryocatactes L.’ < *ranšis / *ranžis) display a different meaning, as well as an unusual variation of stops (voiceless consonant vs. voiced consonant), which could have developed under the influence of Finno-Ugric languages. Indeed, a close equivalent can be found in the Mari language (e.g. West Mari ronγə̑ž ‘spotted nutcracker’). The Balto-Finnic languages display a different variant *närši (metathesized to or from *ränši) in the sense of ‘jay’ as well as a noun *räšni denoting ‘woodpecker’. Presumably Russ. ронжа. dial. роньжа ‘Siberian jay’ represents a loanword borrowed from an extinct Finno-Ugric language, e.g. Meryanic, Muromian or Meshcherian.

Habitat suitability models based on opportunistic citizen science data: Evaluating forecasts from alternative methods versus an individual‐based model

AbstractAimTo evaluate the utility of opportunistic data from citizen science programmes for forecasting species distributions against forecasts with a model of individual‐based population dynamics.LocationSweden.MethodsWe evaluated whether alternative methods for building habitat suitability models (HSMs) based on opportunistic data from citizen science programmes produced forecasts that were consistent with forecasts from two benchmark models: (1) a HSM based on data from systematic monitoring and (2) an individual‐based model for spatially explicit population dynamics based on empirical demographic and movement data. We forecasted population numbers and habitat suitability for three realistic, future forest landscapes for a forest bird, the Siberian jay (Perisoreus infaustus). We ranked simulated forest landscapes with respect to their benefits to Siberian jays for each modelling method and compared the agreement of the rankings among methods.ResultsForecasts based on our two benchmark models were consistent with each other and with expectations based on the species’ ecology. Forecasts from logistic regression models based on opportunistic data were consistent with the benchmark models if species detections were combined with high‐quality inferred absences derived via retrospective interviews with experienced “super‐reporters.” In contrast, forecasts with three other widely used methods were inconsistent with the benchmark models, sometimes with misleading rankings of future scenarios.Main conclusionsOur critical evaluation of alternative HSMs against a spatially explicit IBM demonstrates that information on species absences critically improves forecasts of species distributions using opportunistic data from citizen science programmes. Moreover, high‐quality information on species absences can be retrospectively inferred from surveys of the consistency of reporting of individual species and the identification skills of participating reporters. We recommend that citizen science projects incorporate procedures to evaluate reporting behaviour. Inferred absences may be especially useful for improving forecasts for species and regions poorly covered by systematic monitoring schemes.

Forest management affects seasonal source-sink dynamics in a territorial, group-living bird

The persistence of wildlife populations is under threat as a consequence of human activities, which are degrading natural ecosystems. Commercial forestry is the greatest threat to biodiversity in boreal forests. Forestry practices have degraded most available habitat, threatening the persistence of natural populations. Understanding population responses is, therefore, critical for their conservation. Population viability analyses are effective tools to predict population persistence under forestry management. However, quantifying the mechanisms driving population responses is complex as population dynamics vary temporally and spatially. Metapopulation dynamics are governed by local dynamics and spatial factors, potentially mediating the impacts of forestry e.g., through dispersal. Here, we performed a seasonal, spatially explicit population viability analysis, using long-term data from a group-living territorial bird (Siberian jay, Perisoreus infaustus). We quantified the effects of forest management on metapopulation dynamics, via forest type-specific demography and spatially explicit dispersal, and how forestry impacted the stability of metapopulation dynamics. Forestry reduced metapopulation growth and stability, through negative effects on reproduction and survival. Territories in higher quality natural forest contributed more to metapopulation dynamics than managed forests, largely through demographic processes rather than dispersal. Metapopulation dynamics in managed forest were also less resilient to disturbances and consequently, may be more vulnerable to environmental change. Seasonal differences in source-sink dynamics observed in managed forest, but not natural forests, were caused by associated seasonal differences in dispersal. As shown here, capturing seasonal source-sink dynamics allows us to predict population persistence under human disturbance and to provide targeted conservation recommendations.

Who do you trust? Wild birds use social knowledge to avoid being deceived.

Many species give deceptive warning calls, enabled by the high risk of ignoring them. In Siberian jays, a territorial, group-living bird, individuals give warning calls toward perched predators and mob them. However, intruding neighbors can emit these warning calls in the absence of predators to access food, but breeders often ignore these calls. Playback field experiments show that breeders flee sooner and return later after warning calls of former group members than those of neighbors or unknown individuals. Thus, breeders respond appropriately only to warning calls of previous cooperation partners. This mechanism facilitates the evolution and maintenance of communication vulnerable to deceptive signaling. This conclusion also applies to human language because of its cooperative nature and thus, its vulnerability to deception.

Территориальные связи, гнездовой консерватизм, дисперсия и филопатрия кукши Perisoreus infaustus (Passeriformes, Aves) в Якутии

Studies were conducted within two species model sites (471 and 1360.3 ha) in the middle taiga light-coniferous forests near the city Yakutsk (62° N, 129° E) in 1975-2015. The Siberian jay inhabits a variety of landscape conditions and is very plastic when choosing a nesting site and a place for the nest. A significant part of breeding birds are characterized by conservatism manifested in the presence of permanent habitats with nesting sites and nesting locations. Individual tagging data indicate that most chicks left the model sites (were died or emigrated). Only a small percentage of young birds stayed within the local population, joining territorial pairs as a third сinertт partner, and later, having acquired a partner and a territory, being included in the reproductive population.

Genetic differentiation in Sichuan jay (Perisoreus internigrans) and its sibling species Siberian jay (P. infaustus)

The Pleistocene ice age and recent forest fragmentation have both played a significant role in shaping the population genetic variation of boreal coniferous species in the Qinghai-Tibet Plateau (QTP) and Eurasian coniferous forests. The Sichuan jay is one of the least know endemic bird species in QTP coniferous forests in western China while its sibling species, the Siberian Jay, is widespread within the coniferous forests in northern Eurasia. Here we used 11 microsatellite markers to assay genetic diversity across 58 Sichuan jay samples from China and 205 Siberian jay samples from Sweden and Russia. Results showed three distinct genetic clusters from the Sichuan jay sampling. Furthermore, the pair-wise FST values indicated high genetic differentiation not only among the two species but also between Swedish and Russian Siberian jay populations. What is more, a pattern of isolation by distance was found among the analyzed populations. Our study suggests that targeted habitat restoration in fragmented forests and more genetic work is urgently needed for conservation of the Sichuan jay.

Remotely sensed forest understory density and nest predator occurrence interact to predict suitable breeding habitat and the occurrence of a resident boreal bird species.

Habitat suitability models (HSM) based on remotely sensed data are useful tools in conservation work. However, they typically use species occurrence data rather than robust demographic variables, and their predictive power is rarely evaluated. These shortcomings can result in misleading guidance for conservation. Here, we develop and evaluate a HSM based on correlates of long‐term breeding success of an open nest building boreal forest bird, the Siberian jay. In our study site in northern Sweden, nest failure of this permanent resident species is driven mainly by visually hunting corvids that are associated with human settlements. Parents rely on understory nesting cover as protection against these predators. Accordingly, our HSM includes a light detection and ranging (LiDAR) based metric of understory density around the nest and the distance of the nest to the closest human settlement to predict breeding success. It reveals that a high understory density 15–80 m around nests is associated with increased breeding success in territories close to settlements (<1.5 km). Farther away from human settlements breeding success is highest at nest sites with a more open understory providing a favorable warmer microclimate. We validated this HSM by comparing the predicted breeding success with landscape‐wide census data on Siberian jay occurrence. The correlation between breeding success and occurrence was strong up to 40 km around the study site. However, the HSM appears to overestimate breeding success in regions with a milder climate and therefore higher corvid numbers. Our findings suggest that maintaining patches of small diameter trees may provide a cost‐effective way to restore the breeding habitat for Siberian jays up to 1.5 km from human settlements. This distance is expected to increase in the warmer, southern, and coastal range of the Siberian jay where the presence of other corvids is to a lesser extent restricted to settlements.

Hit or miss? Evaluating the effectiveness of Natura 2000 for conservation of forest bird habitat in Sweden

Biodiversity conservation often requires a landscape perspective. When establishing the Natura 2000 (N2k) network, the effectiveness of the sites and the influence of the surrounding landscapes for species of interest was often disregarded. We analyzed the effectiveness of N2k sites in Sweden for three forest bird species of conservation interest in the European boreal landscapes: lesser spotted woodpecker (LSW), Siberian jay (SJ) and hazel grouse (HG). Our objectives were to: 1) quantify effective suitable habitat area in N2k sites with and without consideration of the adjoining landscapes; 2) examine effective habitat area within N2k sites along the north-south vegetation gradient 3) analyze functionality of N2k sites and assess how forests outside the sites affect habitat suitability inside N2k. GIS-based habitat suitability index models were applied to calculate the amount of effective habitat within and outside N2k sites. N2k sites contributed with 10% (HG), 13% (SJ) and 51% (LSW) suitable habitat identified in Sweden. Functionality of forest environments as habitat was higher inside N2k sites for LSW within all vegetation zones, and for SJ in the Alpine and Middle Boreal zones; for HG habitat outside the sites was more functional in all zones accept Alpine and Middle Boreal. The majority of N2k sites were of quite small size (<500 ha) and the size influenced their functionality for LSW and HG, with larger N2k sites being more functional. For SJ, however, average functionality of N2k sites was not influenced by their size. The largest average habitat increase linked to considering the contribution of areas outside N2k sites for their functionality as habitat was for the N2k sites of smaller size (1-500 ha). Therefore, the presence and quality of forests outside of N2k sites are of a greater importance for smaller sites, and as such these should be carefully managed. To improve conservation efficiency of the N2k sites in Sweden, we call for incorporating them into the development and implementation of the regional Green Infrastructure plans.

Ecological restoration modifies the value of biodiversity indicators in resident boreal forest birds

A wide range of different biodiversity indicators have been identified in different biomes and types of environments. However, we currently lack a clear understanding under which circumstances proposed biodiversity indicators are valid indicators and when they are not. Here we conducted a large-scale restoration experiment by emulating natural disturbances through prescribed burning and gap-cutting. From this experiment data of resident forest birds was used to, (1) identify biodiversity indicators in the middle and northern boreal zone, (2) test the effect of forest restoration practices on biodiversity indicators and (3) explore the patterns when biodiversity indicator analyses are performed across a wider range of forest types including both restored and unrestored sites. Additionally, to understand the occurrence of species we correlated their occurrence with local habitat structures across different forest types. We found that both the three-toed woodpecker (Picoides tridactylus) and Siberian jay (Perisoreus infaustus) were important biodiversity indicators for the middle/northern boreal zone. The occurrence of these species can generally be used to identify species rich areas across different forest types. However, the three-toed woodpecker, the best indicator for unrestored forest, lost its indicator value after prescribed burning; in these stands the goldcrest (Regulus regulus) was the best biodiversity indicator. Based on habitat associations, we suggest that biodiversity indicators in boreal forest not only indicate high species richness but also structural habitat complexity. Our results draw attention to the fact that one must be careful about using previously identified biodiversity indicators in ecosystems subjected to ecological restoration.

Responses of Blue Jays (Cyanocitta Cristata) to Raptors that Differ in Predatory Threat

Some species of birds use their vocalisations to communicate predator presence and the level of threat they pose, including two species of corvids (Corvidae), American Crows (Corvus brachyrhynchos) and Siberian Jays (Perisoreus infaustus). Our objective was to determine if Blue Jays (Cyanocitta cristata), another corvid, also use specific calls or vary the characteristics of certain calls to convey information about the level of threat posed by aerial predators. During the non-breeding seasons of 2014 and 2015, we recorded and analysed the vocal responses of Blue Jays to study skins of six species of raptors that varied in size and the level of threat they pose to Blue Jays. Experiments were conducted at seven locations in Madison County, Kentucky. The mean number of Blue Jays present during trials was 2.6, and Blue Jays uttered five different vocalisations during trials, with ditonal and monotonal jeers given most frequently. The rate at which Blue Jays uttered ditonal jeers differed among trials, with rates highest during trials with an Eastern Screech-Owl (Megascops asio) and a Sharp-shinned Hawk (Accipiter striatus). However, the characteristics of ditonal and monotonal jeers (duration, low frequency, high frequency, and peak frequency) did not differ among trials. These results suggest that Blue Jays may either perceive Eastern Screech-Owls and Sharp-shinned Hawks as the greatest threats or, alternatively, as potential, but less threatening predators, and, therefore, they were willing to take greater risks when mobbing them. In contrast, Blue Jays mobbed the other raptors, i.e. American Kestrels (Falco sparverius), Red-tailed Hawks (Buteo jamaicensis), and Great Horned Owls (Bubo virginianus), with much less intensity, likely because they posed less of a threat or, in the case of Cooper's Hawks (Accipiter cooperii) that are known predators of Blue Jays, perhaps because mobbing with greater intensity, e.g. approaching more closely, posed too great a risk. Blue Jays in our study used the same calls with the same characteristics when responding to potential predators, only calling rates differed. However, such variation in calling rates when mobbing would likely provide useful information about the presence of, and possibly the threat posed by, potential predators for conspecifics and, perhaps, heterospecifics.

Can opportunistically collected Citizen Science data fill a data gap for habitat suitability models of less common species?

AbstractOpportunistically collected species observations contributed by volunteer reporters are increasingly available for species and regions for which systematically collected data are not available. However, it is unclear if they are suitable to produce reliable habitat suitability models (HSMs), and hence if the species–habitat relationships found and habitat suitability maps produced can be used with confidence to advice conservation management and address basic and applied research questions.We evaluated HSMs with opportunistically collected observations against HSMs with systematically collected observations. We enhanced the opportunistically collected presence‐only data by adding inferred species absences. To obtain inferred absences, we asked individual reporters about their identification skills and if they reported certain species consistently and combined this information with their observations. We evaluated several HSM methods using a forest bird species, Siberian jay (Perisoreus infaustus), in Sweden: logistic regression with inferred absences, two versions of MaxEnt, a model combining presence–absence with presence‐only observations and a Bayesian site‐occupancy‐detection model.All HSM methods produced nationwide habitat suitability maps of Siberian jay that agreed well with systematically collected observations (AUC: 086–0.88) and were very similar to a habitat suitability map produced from the HSM with systematically collected observations (Spearman rho: 0.94–0.98). At finer geographical scales there were differences among methods.At finer scale, the resulting habitat suitability maps from logistic regression with inferred absences agreed better with results from systematically collected observations than other methods. The species–habitat relationships found with logistic regression also agreed well with those found from systematically collected data and with prior expectations based on the species ecology.Synthesis and application. For many regions and species, systematically collected data are not available. By using inferred absences from high‐quality, opportunistically collected contributions of few very active reporters in logistic regression we obtained HSMs that produced results similar to those from a systematic survey. Adding high‐quality inferred absences to opportunistically collected data is likely possible for many less common species across various organism groups. Well‐performing HSMs are important to facilitate applications such as spatial conservation planning and prioritization, monitoring of invasive species, understanding species habitat requirements or climate change studies.

The interacting effects of forestry and climate change on the demography of a group-living bird population.

Anthropogenic degradation of natural habitats is a global driver of wildlife population declines. Local population responses to such environmental perturbations are generally well understood, but in socially structured populations, interactions between environmental and social factors may influence population responses. Thus, understanding how habitat degradation affects the dynamics of these populations requires simultaneous consideration of social and environmental mechanisms underlying demographic responses. Here we investigated the effect of habitat degradation through commercial forestry on spatiotemporal dynamics of a group-living bird, the Siberian jay, Perisoreus infaustus, in boreal forests of northern Sweden. We assessed the interacting effects of forestry, climate and population density on stage-specific, seasonal life-history rates and population dynamics, using long-term, individual-based demographic data from 70 territories in natural and managed forests. Stage-specific survival and reproductive rates, and consequently population growth, were lower in managed forests than in natural forests. Population growth was most sensitive to breeder survival and was more sensitive to early dispersing juveniles than those delaying dispersal. Forestry decreased population growth in managed forests by reducing reproductive success and breeder survival. Increased snow depth improved winter survival, and warmer spring temperatures enhanced reproductive success, particularly in natural forests. Population growth was stable in natural forests but it was declining in managed forests, and this difference accelerated under forecasted climate scenarios. Thus, climatic change could exacerbate the rate of forestry-induced population decline through reduced snow cover in our study species, and in other species with similar life-history characteristics and habitat requirements.

Are wintering Common Redpolls &lt;i&gt;Carduelis flammea&lt;/i&gt; more exposed to avian predators than other small passerines?

The Common Redpoll Carduelis flammea is a highly social flocking bird which forms cohesive groups outside the breeding season. Being small birds (12-15g), they need to forage almost continuously during a few hours of daylight in winter to meet their energy demands. Although predation risk is reduced as a result of improved surveillance of many eyes, increased flock size may also increase the agonistic interactions among individuals within the flock and as a consequence lower the probability of detection of a predator’s approach. To examine whether Common Redpolls, living in relatively large winter flocks, are more exposed to avian predators than small passerines living in groups of only a few individuals, I recorded the responses of Common Redpolls, Willow Tits Poecile montanus and Great Tits Parus major to a life-like stuffed specimen of two different predators, the Siberian Jay Perisoreus infaustus (body length 30 cm) and the Hooded Crow Corvus cornix (50 cm). After the presentation of a predator model, Redpolls returned to the seed sites on the average earlier than the tits, and significantly so versus both tit species after exposure to the Siberian Jay, and for Great Tits after exposure to the Hooded Crow. Whereas Willow and Great Tits seemed to pick up sunflower seeds in the snow without much competition, Common Redpolls displayed a more conspicuous, aggressive, intraspecific behaviour. Thus, the individual vigilance of Common Redpolls was most likely reduced and exposure time to predation increased. The seed-eating Common Redpolls may be more food-stressed than the year-round resident Willow Tits that have stored food within their territories. If so, Common Redpolls may be forced to take greater predation risks because of a higher hunger level. If the differences in return times after exposure to a predator model reflected an adaptation to perceived predation risk, the Common Redpolls apparently evaluated the Siberian Jay as less dangerous than did the tits.

Predator discrimination and anti-predator behaviour by wintering parids: an experimental study

Even though birds’ perceptions of risk are biased towards starvation avoidance in winter, recognition of the level of threat of a predator is an important precondition. To investigate the ability of three tit species (Blue Cyanistes caeruleus , Great Parus major and Willow Tits Poecile montanus ) to recognise dangerous and harmless objects, I studied their mobbing reaction and the latency of the tits to return to the feeder after being exposed to life like models of Eurasian Sparrowhawk Accipiter nisus , Siberian Jay Perisoreus infaustus and Three-toed Woodpecker Picoides tridactylus , birds similar in size (about 30 cm) but differing widely from each other in feeding. The mobbing level was higher and the latency time of each of the tit species were significantly longer after presenting the Sparrowhawk than the Siberian Jay, whereas the woodpecker aroused no specific reaction. The tits apparently recognised the individual predator species and made decisions on their perceptions of the threat level.

Experience buffers extrinsic mortality in a group‐living bird species

Extrinsic mortality has a strong impact on the evolution of life‐histories, prey morphology and behavioural adaptations, but for many animals the causes of mortality are poorly understood. Predation is an important driver of extrinsic mortality and mobile animals form groups in response to increased predation risk. Furthermore, in many species juveniles suffer higher mortality than older individuals, which may reflect a lower phenotypic quality, lower competitiveness, or a lack of antipredator or foraging skills. Here we assessed the causes of mortality for 371 radio tagged Siberian jays. This sedentary bird species lives in family groups that contain a breeding pair as well as related and unrelated non‐breeders. Ninety‐five percent of death were due to predation (n = 59 out of 62 individuals) and most individuals were killed by Accipiter hawks. Multivariate Cox proportional hazards models showed that non‐breeders had a lower survival than breeders, but only in territories in managed forest with little visual cover. Examining breeders, only sex influenced survival with males having a lower survival than females. For non‐breeders, juveniles had lower survival than older non‐breeders, and those on managed territories had lower survival than those on unmanaged territories. Additionally, a low feather quality reduced the survival probability of non‐breeders only. Thus, living on managed territories and having a low feature quality affected only non‐breeders, particularly juveniles. These findings add to previous research demonstrating that juvenile Siberian jays acquire critical antipredator skills from experienced group members. Thus, experience can buffer extrinsic mortality, highlighting that group living not only provides safety in numbers, but also provide social opportunities to learn critical life‐skills.

Reproductive trade-offs in a long-lived bird species: condition-dependent reproductive allocation maintains female survival and offspring quality.

Life history theory is an essential framework to understand the evolution of reproductive allocation. It predicts that individuals of long-lived species favour their own survival over current reproduction, leading individuals to refrain from reproducing under harsh conditions. Here we test this prediction in a long-lived bird species, the Siberian jay Perisoreus infaustus. Long-term data revealed that females rarely refrain from breeding, but lay smaller clutches in unfavourable years. Neither offspring body size, female survival nor offspring survival until the next year was influenced by annual condition, habitat quality, clutch size, female age or female phenotype. Given that many nests failed due to nest predation, the variance in the number of fledglings was higher than the variance in the number of eggs and female survival. An experimental challenge with a novel pathogen before egg laying largely replicated these patterns in two consecutive years with contrasting conditions. Challenged females refrained from breeding only in the unfavourable year, but no downstream effects were found in either year. Taken together, these findings demonstrate that condition-dependent reproductive allocation may serve to maintain female survival and offspring quality, supporting patterns found in long-lived mammals. We discuss avenues to develop life history theory concerning strategies to offset reproductive costs.

Trends in the Siberian Jay, Perisoreus infaustus, Populations in Southern Norway in Relation to Forestry, Climate Change and other Corvid Species

The Siberian jay Perisoreus infaustus has experienced a large decline due to logging in Finland. Populations may also be at risk due to climate warming and interactions with expanding populations of other corvid species. We assessed causes of Siberian jay population changes in southern Norway by conducting field surveys and an online survey addressed to birdwatchers. Field surveys indicated that density of Siberian jays was related to old-growth forest. Density was lower at sites close to the edge of the southeastern distribution margin. Unexpectedly, presence was positively associated with presence of other corvid species. The online survey indicated decreasing populations in logged areas close to the southeastern distribution margin. Respondents reported an increase of other corvid species, but increases were not correlated with decreases of Siberian jays. The field survey and the online survey did not indicate lower population density or population declines at lower-altitude sites (expected if climate ...

Naive Juveniles Are More Likely to Become Breeders after Witnessing Predator Mobbing.

Responding appropriately during the first predatory attack in life is often critical for survival. In many social species, naive juveniles acquire this skill from conspecifics, but its fitness consequences remain virtually unknown. Here we experimentally demonstrate how naive juvenile Siberian jays (Perisoreus infaustus) derive a long-term fitness benefit from witnessing knowledgeable adults mobbing their principal predator, the goshawk (Accipiter gentilis). Siberian jays live in family groups of two to six individuals that also can include unrelated nonbreeders. Field observations showed that Siberian jays encounter predators only rarely, and, indeed, naive juveniles do not respond to predator models when on their own but do when observing other individuals mobbing them. Predator exposure experiments demonstrated that naive juveniles had a substantially higher first-winter survival after observing knowledgeable group members mobbing a goshawk model, increasing their likelihood of acquiring a breeding position later in life. Previous research showed that naive individuals may learn from others how to respond to predators, care for offspring, or choose mates, generally assuming that social learning has long-term fitness consequences without empirical evidence. Our results demonstrate a long-term fitness benefit of vertical social learning for naive individuals in the wild, emphasizing its evolutionary importance in animals, including humans.