Garrulus Glandarius Research Articles

Usutu virus, Austria and Hungary, 2010–2016

Usutu virus (USUV, Flaviviridae) was first reported in Europe in Austria in 2001, where it caused wild bird (mainly blackbird) mortality until 2005. Since 2006 no further USUV cases were diagnosed in the country. However, the virus emerged in other European countries (Hungary, Italy, Switzerland, Spain, Germany and the Czech Republic) between 2005 and 2011. In 2016, widespread USUV-associated wild bird mortality was observed in Germany, France, Belgium and the Netherlands. In this study, we report the results of passive monitoring for USUV in Austria and Hungary between 2010 and 2016. In Hungary, USUV caused sporadic cases of wild bird mortality between 2010 and 2015 (altogether 18 diagnosed cases), whereas in summer and autumn 2016 the number of cases considerably increased to 12 (ten blackbirds, one Eurasian jay and one starling). In Austria, USUV was identified in two blackbirds in 2016. Phylogenetic analyses of coding-complete genomes and partial regions of the NS5 protein gene revealed that USUVs from Hungary between 2010 and 2015 are closely related to the virus that emerged in Austria in 2001 and in Hungary in 2005, while one Hungarian sequence from 2015 and all sequences from Hungary and Austria from 2016 clustered together with USUV sequences reported from Italy between 2009 and 2010. The results of the study indicate continuous USUV circulation in the region and exchange of USUV strains between Italy, Austria and Hungary.Emerging Microbes & Infections (2017) 6, e85; doi:10.1038/emi.2017.72; published online 11 October 2017

‘Aesop's fable’ experiments demonstrate trial-and-error learning in birds, but no causal understanding

Experiments inspired by Aesop's fable The crow and the pitcher have been suggested to show that some birds (rooks, Corvus frugilegus, New Caledonian crows, Corvus moneduloides, and Eurasian jays, Garrulus glandarius) understand cause–effect relationships pertaining to water displacement. For example, the birds may prefer to drop stones in water rather than in sand in order to retrieve a floating food morsel, suggesting that they understand that only the level of water can be so raised. Here we re-evaluate the evidence for causal understanding in all published experiments (23 928 choices by 36 individuals). We first show that commonly employed statistical methods cannot disentangle the birds' initial performance on a task (which is taken as an indicator of causal understanding) from trial-and-error learning that may occur during the course of the experiment. We overcome this shortcoming with a new statistical analysis that quantifies initial performance and learning effects separately. We present robust evidence of trial-and-error learning in many tasks, and of an initial preference in a few. We also show that both seeming demonstrations of causal understanding and of lack of it can be understood based on established properties of instrumental learning. We conclude that Aesop's fable experiments have not yet produced evidence of causal understanding, and we suggest how the experimental designs can be modified to yield better tests of causal cognition.

Provision of supplementary food for wild birds may increase the risk of local nest predation

In countries such as the UK, USA and Australia, approximately half of all households provide supplementary food for wild birds, making this the public's most common form of active engagement with nature. Year‐round supplementary feeding is currently encouraged by major conservation charities in the UK as it is thought to be of benefit to bird conservation. However, little is understood about how the provision of supplementary food affects the behaviour and ecology of target and non‐target species. Given the scale of supplementary feeding, any negative effects may have important implications for conservation. Potential nest predators are abundant in urban areas and some species frequently visit supplementary feeding stations. We assess whether providing supplementary food affects the likelihood of nest predation in the vicinity of the feeder, by acting as a point attractant for potential nest predators. We provided feeding stations (empty, peanut feeder, peanut feeder with guard to exclude potential nest predators) in an area of suburban parkland in the UK and monitored the predation rate of eggs placed in artificial nests located at distances that replicated the size of typical suburban gardens. Nest predators (Magpies Pica pica, Grey Squirrels Sciurus carolinensis) were frequent visitors to filled feeders, and predation caused by Magpies, European Jays Garrulus glandarius and Grey Squirrels was significantly higher when nests were adjacent to filled feeders. The presence of a feeder guard did not significantly reduce nest predation. As supplementary feeding is becoming increasingly common during the breeding season in suburban habitats, we suggest that providing point attractants to nest predators at this time may have previously unconsidered consequences for the breeding success of urban birds.

Eurasian jays do not copy the choices of conspecifics, but they do show evidence of stimulus enhancement.

Corvids (birds in the crow family) are hypothesised to have a general cognitive tool-kit because they show a wide range of transferrable skills across social, physical and temporal tasks, despite differences in socioecology. However, it is unknown whether relatively asocial corvids differ from social corvids in their use of social information in the context of copying the choices of others, because only one such test has been conducted in a relatively asocial corvid. We investigated whether relatively asocial Eurasian jays (Garrulus glandarius) use social information (i.e., information made available by others). Previous studies have indicated that jays attend to social context in their caching and mate provisioning behaviour; however, it is unknown whether jays copy the choices of others. We tested the jays in two different tasks varying in difficulty, where social corvid species have demonstrated social information use in both tasks. Firstly, an object-dropping task was conducted requiring objects to be dropped down a tube to release a food reward from a collapsible platform, which corvids can learn through explicit training. Only one rook and one New Caledonian crow have learned the task using social information from a demonstrator. Secondly, we tested the birds on a simple colour discrimination task, which should be easy to solve, because it has been shown that corvids can make colour discriminations. Using the same colour discrimination task in a previous study, all common ravens and carrion crows copied the demonstrator. After observing a conspecific demonstrator, none of the jays solved the object-dropping task, though all jays were subsequently able to learn to solve the task in a non-social situation through explicit training, and jays chose the demonstrated colour at chance levels. Our results suggest that social and relatively asocial corvids differ in social information use, indicating that relatively asocial species may have secondarily lost this ability due to lack of selection pressure from an asocial environment.

Experimenter expectancy bias does not explain Eurasian jays' (Garrulus glandarius) performance in a desire-state attribution task.

Male Eurasian jays have been found to adjust the type of food they share with their female partner after seeing her eat 1 type of food to satiety. One interpretation of this behavior is that the male encoded the female's decreased desire for the food she was sated on, and adjusted his behavior accordingly. However, in these studies, the male's actions were scored by experimenters who knew on which food the female was sated. Thus, it is possible that the experimenters' expectations (subconsciously) affected their behavior during tests that, in turn, inadvertently could have influenced the males' actions. Here, we repeated the original test with an experimenter who was blind to the food on which the female was sated. This procedure yielded the same results as the original studies: The male shared food with the female that was in line with her current desire. Thus, our results rule out the possibility that the Eurasian jay males' actions in the food sharing task could be explained by the effects of an experimenter expectancy bias. (PsycINFO Database Record

Shifting demographic conflicts across recruitment cohorts in a dynamic post-disturbance landscape.

Seed dispersal effectiveness, which measures the number of adult plant individuals produced by seed dispersal, is the product of the number of seeds dispersed and the probability a seed produces an adult. Directed dispersal to certain habitat types may enhance some stages of recruitment but disfavor others, generating demographic conflicts in plant ontogeny. We asked whether temporal changes in habitat features may affect the distribution of seedlings recruited from dispersed acorns, and whether this could induce shifts in the life-stage conflicts experienced by successive cohorts of naturally recruited plants. As early successional habitats are characterized by rapid change, we used a burnt pine stand in southern Spain to monitor the recruitment and performance of a major tree species (Quercus ilex) across 7 yr in four types of post-fire habitats. These differed in structure and included patches of unburnt forest and three management alternatives of burnt trees: logging, partial cutting, and nonintervention. Young oaks that resprouted after the fire were mainly located near acorn sources, while new seedlings initially emerged mostly in habitats with standing snags due to habitat selection by European jays, Garrulus glandarius, for dispersal. The dead pines gradually collapsed and attracted less dispersal, so subsequent seedling cohorts mainly recruited within patches of unburnt pines. These live pines enhanced the survival of the oaks located beneath their canopy but greatly reduced their growth as compared to the other post-fire habitats, thus representing a demographic conflict that was absent elsewhere. As a consequence of the directional shift in the habitat where seedlings recruited, successive seedling cohorts experienced a gradual improvement in their likelihood of survival but a reduction in growth. The progressive intensification of this life-stage conflict hinged on the reduction of vertical structures in the habitat with standing burnt pines. Recruitment success thus involved temporal variation in the habitat where recruitment occurred, likely resulting from changes in the direction of seed dispersal, and spatial variation in habitat suitability for seedling establishment and growth. Temporal changes in habitat structure can indirectly change the environment in which recruitment occurs, and consequently seed dispersal effectiveness, by shifting the direction of seed dispersal.

Spatial patterns of seasonal distribution of Corvidae (the case of urban habitats)

Corvids in Zhytomyr city reach maximum density in the winter period. Rooks and Eurasian Jackdaws were the most abundant species in winter, usually feeding in multispecies flocks and forming collective roosts.Suburban green areas (buffer zones) were characterized by a considerably high diversity of Corvidae species: this habitat was occupied by all six species. We also registered the highest density of Eurasian Jays and Hooded Crows in this habitat. The green areas in the city center were also characterized by significant corvid density, especially during the breeding season. The maximum breeding density of Rooks was in these habitats, which held 6 of 12 identified urban colonies in Zhytomyr. We found that the European Magpies, Eurasian Jays, and Hooded Crows also had high breeding success here. Eurasian Jackdaws occurred here only in autumn and winter, when they fed together with Rooks on lawns, gardens, and parks. With stable snow cover the Rook density in habitats of the green areas decreased due to the depletion of food resources.The individual buildings zone of the city were characterized by the lowest density of all corvid species, except for European Magpies and Eurasian Jays. The number of common species (Rooks, Eurasian Jackdaws, and Hooded Crows) was low because of shortage of food resources, lack of sites for large roosting flocks and shortage of suitable nesting sites. However, Eurasian Magpies reached one of their highest densities in this habitat (12.8 birds/km2). This species was registered in habitats around private buildings all the year round, successfully nesting in the yards of private houses and on trees in the streets. Its breeding density was 11.2 birds/km2.During three years of research (2009–2012) the density of all corvids except for European Magpie, practically did not change, although we determined a slight positive trend for all the species. The strong increase in the number of Eurasian Jackdaws could be explained by the increasing density of wintering populations or due to the increasing number of migrants from more northern regions.

Spatial patterns of habitat distribution of Corvidae (the case of urban-rural gradient)

The spatial distribution and abundance of Corvidae species in Zhytomyr region was studied in terms of the urban-rural gradient. We selected Rook (Corvus frugilegus L.), Eurasian Jackdaw (C. monedula L.), Hooded Crow (C. cornix L.), Common Raven (C. corax L.), Eurasian Magpie (Pica pica L.) and Eurasian Jay (Garrulus glandarius L.) for our observations during 2009–2012. Some 38 survey routes totaling more than 8000 km were surveyed in 21 settlements in Zhytomyr region. Among them 13 routes were in Zhytomyr city. The average density of Rooks was 55.9 birds/km2. We found a strong correlation between Rook density and rural-urban gradient and observed that the numbers of wintering Rooks in cities significantly increased due to the influx from villages. The peak number of Rooks in villages was registered in the breeding and post-breeding seasons while in the cities it was high in winter and during the spring migration. The average density of Eurasian Magpies in the study area was 8.7 birds/km2 and we registered weak correlation with the urban-rural gradient. Their maximum density in urban habitats was in the winter period whereas the highest density in rural habitats was fixed in the summer months. The density of Magpies varied insignificantly within a narrow range during the three years of research, which suggests the species has successfully adjusted to the transformed landscapes. Average density of Hooded Crows in towns was 6.6 birds/km2. The linear relationship between the urban-rural gradient and the density of this species was rather weak. In the breeding period, the birds’ density was considerably higher in urban habitats. We also registered that the average density of Hooded Crows changed insignificantly but gradually increased during the study period. The average density of Eurasian Jackdaws was 9.7 birds/km2 and had high annual dynamics. It also changed significantly during the three years of research. The average density of Eurasian Jays was 2.4 birds/km2 and varied significantly in different settlements, although the fluctuation range was small (0.1–9.3 birds/km2). We registered an expansion in the breeding distribution of Eurasian Jays in recent years i.e. the birds began to nest in old urban neighborhoods and small central parks of large cities. However, the number of birds naturally decreased along the gradient of landscape transformation. The impact of urban-rural gradient on Eurasian Jay density was significant but the correlation was weak and negative. The density of this species was highest in small villages (4.9 birds/km2) and the lowest in medium-sized cities (1.5 birds/km2). The seasonal density of Jays varied significantly and the greatest value was registered in the post-breeding period. In urban areas the birds’ density was much higher in winter compared to the nesting period, and in villages we observed the reverse situation. The number of Eurasian Jays remained almost stable in all the settlements during the study period indicating the stability of the local populations. The average density of the Common Raven was 1.3 birds/km2 and the highest density was registered in small villages (2.2 birds/km2), the lowest – in the townships (small urban type settlements) (0.6 birds/km2). The urban-rural gradient significantly affected the spatial distribution of Common Ravens, but we cannot claim an increase or decrease in their numbers along the gradient of urbanization, since the value of this indicator also depended on habitat conditions in each specific settlement. The spatial distribution of Common Ravens varied seasonally and the highest density was typical in winter due to food migrations towards human settlements.

Facing a Clever Predator Demands Clever Responses - Red-Backed Shrikes (Lanius collurio) vs. Eurasian Magpies (Pica pica).

Red-backed shrikes (Lanius collurio) behave quite differently towards two common nest predators. While the European jay (Garrulus glandarius) is commonly attacked, in the presence of the Eurasian magpie (Pica pica), shrikes stay fully passive. We tested the hypotheses that this passive response to the magpie is an alternative defense strategy. Nesting shrikes were exposed to the commonly attacked European kestrel (Falco tinnunculus) in a situation in which i) a harmless domestic pigeon, ii) a commonly attacked European jay, and iii) a non-attacked black-billed magpie are (separately) presented nearby. The kestrel dummy presented together with the magpie dummy was attacked with a significantly lower intensity than when it was presented with the other intruders (pigeon, jay) or alone. This means that the presence of the magpie inhibited the shrike’s defense response towards the other intruder. These results support our previous hypotheses that shrikes use an alternative defense strategy in the magpie’s presence. We hypothesize that the magpie is able to associate the active defense of the shrikes with the close proximity of a nest and that shrikes try not to draw the magpie’s attention to the nest. The reason why this strategy is not used against the jay remains unanswered as jays as well as magpies show very similar cognitive and foraging skills enabling them to individuate the nest presence according to active parental defense.

Acorns of introduced Quercus rubra are neglected by European Jay but spread by mice

Northern Red Oak (Quercus rubra L.; native in North America) is regarded as an invasive species in Central Europe, where it is the most common non-indigenous broad-leafed tree species in forestry. The species’ impact on native ecosystems and thus its future management are discussed controversially. Because dispersal is an important step in an invasion process, we studied whether European Jays (Garrulus glandarius L.) and mice, both main dispersers of native oaks in Europe, mediate the dispersal of Q. rubra seeds. Morphological characteristics of Q. rubra and native Q. robur L. acorns were quantified according to their implications for dispersal. We tested experimentally whether and to what extent mice and jays collect acorns of both oak species and if their behavior depends on choice options (dual choice vs. no-choice). Acorns were offered on feeding platforms, controlled by scouting cameras. Results showed that Q. rubra acorns have a thicker pericarp, a rounder shape and a higher dry weight compared to acorns of Q. robur. In the behavioral assays jays avoided acorns of Q. rubra if they were offered together with those of Q. robur (dual choice) as well as when Q. rubra acorns were offered alone (no-choice). This selection behavior could be caused by the differences in morphological traits observed between the acorns of the two species. In contrast to jays, mice took acorns of both oak species likewise indicating that seed morphology does not affect the attractiveness of Red Oak acorns for rodents. In conclusion, Quercus rubra is collected by animals in Central Europe to a considerable amount but dispersal should be restricted to moderate distances mediated by mice, leading mainly to stabilizing and increasing existing populations rather than founding of new ones.

Caching at a distance: a cache protection strategy in Eurasian jays.

A fundamental question about the complexity of corvid social cognition is whether behaviours exhibited when caching in front of potential pilferers represent specific attempts to prevent cache loss (cache protection hypothesis) or whether they are by-products of other behaviours (by-product hypothesis). Here, we demonstrate that Eurasian jays preferentially cache at a distance when observed by conspecifics. This preference for a ‘far’ location could be either a by-product of a general preference for caching at that specific location regardless of the risk of cache loss or a by-product of a general preference to be far away from conspecifics due to low intra-species tolerance. Critically, we found that neither by-product account explains the jays’ behaviour: the preference for the ‘far’ location was not shown when caching in private or when eating in front of a conspecific. In line with the cache protection hypothesis we found that jays preferred the distant location only when caching in front of a conspecific. Thus, it seems likely that for Eurasian jays, caching at a distance from an observer is a specific cache protection strategy.Electronic supplementary materialThe online version of this article (doi:10.1007/s10071-016-0972-7) contains supplementary material, which is available to authorized users.

Spatial distribution of Corvidae in transformed landscapes of Zhytomyr region

The spatial distribution and abundance of Corvidae species was studied in Zhytomyr region with a focus on rural and urban differences in the studied parameters. We selected Rook (Corvus frugilegus L.), Western Jackdaw (C. monedula L.), Hooded Crow (C. cornix L.), Eurasian Magpie (Pica pica L.), Eurasian Jay (Garrulus glandarius L.), and Common Raven (Corvus corax L.). All observations were made during 2009–2012. During the study period some 38 survey paths of more than 8,000 km were surveyed in 21 settlements of Zhytomyr region, among them 13 were in Zhytomyr city. The aim of our study was to establish the number and density of Corvidae in different seasons in the settlements of Zhytomyr region along a rural-urban gradient. The average density of Rooks was 55.9 ind./km2. We also found a strong correlation between Rook density and the rural-urban gradient and observed that the number of Rooks wintering in cities significantly increased due to the influx from villages. The peak number of Rooks in villages was registered in the breeding and post-breeding season while in the cities it was high in winter and during the spring migration. The average density of Eurasian Magpie in the study area was 8.7 ind./km2 and had a weak correlation with the urban-rural gradient. The density of Eurasian Magpies in urban areas differs significantly only from the density of birds in villages with a population of ca. 1,000 people. The density of Magpies varied insignificantly within a narrow range during the three years of research, remaining relatively stable, which suggests that the species successfully adjusts to conditions in transformed landscapes. The urban-rural gradient significantly affects the density of Hooded Crows. The average density of birds in towns was 6.6 ind./km2. In breeding period the urban birds had a low density and rural crows, on the contrary, had a high density, the density of birds in the nesting period was greater than in autumn and winter, due to the distribution of birds in their breeding territories and the start of the reproductive cycle. The average density of Eurasian Jackdaw was 9.7 ind./km2 and the rural-urban gradient significantly affected the number of birds. For jackdaws we registered high annual population dynamics. The peak number of birds was observed in the winter period in cities and small towns while in villages it was registered in the breeding and post-breeding season. The average density of Eurasian Jay was 2.4 ind./km2 and varied significantly in different settlements, although the fluctuation range was small (0.1–9.3 ind./km2). The number of this species naturally decreases along the gradient of landscape transformation. The highest average density was typical in small villages (4.9 ind./km2) and the lowest was found in medium-sized cities (1.5 ind./km2). We have identified certain patterns in the seasonal dynamic of Eurasian Jays relative to the type of settlement. In urban areas the birds’ density was much higher in winter compared to the nesting period, and in villages we observed the reverse situation. The average density of Common Raven was 1.3 ind./km2. The highest density was registered in small villages and was 2.2 ind./km2, and the smallest in the villages of urban type (0.6 ind./km2). The urban-rural gradient significantly affected the spatial distribution of Common Raven, but we cannot state that this bird increased or decreased its number along the gradient of urbanization, since the value of this indicator also depended on habitat conditions in specific settlements. The spatial distribution of Common Ravens varied seasonally and the highest density was typical in winter due to food migrations to human settlements.

Desire-state attribution: Benefits of a novel paradigm using the food-sharing behavior of Eurasian jays (Garrulus glandarius)

ABSTRACTIn recent years, we have investigated the possibility that Eurasian jay food sharing might rely on desire-state attribution. The female's desire for a particular type of food can be decreased by sating her on it (specific satiety) and the food sharing paradigm can be used to test whether the male's sharing pattern reflects the female's current desire. Our previous findings show that the male shares the food that the female currently wants. Here, we consider 3 simpler mechanisms that might explain the male's behavior: behavior reading, lack of self-other differentiation and behavioral rules. We illustrate how we have already addressed these issues and how our food sharing paradigm can be further adapted to answer outstanding questions. The flexibility with which the food sharing paradigm can be applied to rule out alternative mechanisms makes it a useful tool to study desire-state attribution in jays and other species that share food.

Spatially modulated structural colour in bird feathers.

Eurasian Jay (Garrulus glandarius) feathers display periodic variations in the reflected colour from white through light blue, dark blue and black. We find the structures responsible for the colour are continuous in their size and spatially controlled by the degree of spinodal phase separation in the corresponding region of the feather barb. Blue structures have a well-defined broadband ultra-violet (UV) to blue wavelength distribution; the corresponding nanostructure has characteristic spinodal morphology with a lengthscale of order 150 nm. White regions have a larger 200 nm nanostructure, consistent with a spinodal process that has coarsened further, yielding broader wavelength white reflectance. Our analysis shows that nanostructure in single bird feather barbs can be varied continuously by controlling the time the keratin network is allowed to phase separate before mobility in the system is arrested. Dynamic scaling analysis of the single barb scattering data implies that the phase separation arrest mechanism is rapid and also distinct from the spinodal phase separation mechanism i.e. it is not gelation or intermolecular re-association. Any growing lengthscale using this spinodal phase separation approach must first traverse the UV and blue wavelength regions, growing the structure by coarsening, resulting in a broad distribution of domain sizes.

Landscape effects on jay foraging behavior decrease acorn dispersal services in dehesas

Dehesas are savanna-like, oak woodlands with a high conservation value that are threatened by chronic regeneration failure. Acorn dispersal by Eurasian jays (Garrulus glandarius) is vital for oak recruitment although jay preference for continuous forests may condition this mutualism in dehesas. In this study, we evaluated whether the acorn dispersal services provided by jays to oaks differed between both habitats and assessed factors that could potentially drive such differences. We (1) monitored acorn removal rates at feeders located close to focal trees in a holm oak (Quercus ilex) forest and in a nearby dehesa over a 6-year period; (2) measured the spatial traits of focal trees and their acorn production; and (3) monitored dispersal distances and microhabitat selection for acorn caching during 2012.Our results indicated that jays were able to exploit dehesas located close to forest habitats, but did so infrequently and as a secondary food source (acorn removal rates were six times lower in dehesa than in nearby forests). This likely occurred because dehesas did not offer new or more abundant food sources on a landscape scale. In forests, tree choice was driven by crop traits while in dehesas it was driven by spatial location. Jays preferentially foraged at dehesa trees near forest patches and aggregated to other trees, regardless of crop traits. Acorns were mobilized four times closer in dehesas, and seeds were preferentially cached in unsuitable microhabitats for seedling establishment. Our results suggest that (i) distance to forest habitats and tree isolation effects on jay foraging behavior reduces their dispersal services in dehesas as compared to nearby forests, and (ii) practices designed to enhance acorn dispersal by jays in this habitat should focus on the maintenance or creation of forest patches interspersed within dehesa areas.

Avoiding predators in a fluctuating environment: responses of the wood warbler to pulsed resources

Deciduous forests are characterized by the production of seed crops that may vary dramatically among years. In response to these pulsed resources, rodent populations grow rapidly, which may have crucial consequences for entire forest communities, including songbirds. It has been hypothesized that in response to these rodent outbreaks, the wood warbler Phylloscopus sibilatrix may exhibit nomadic behavior to avoid nest predation. We used data from the Polish Common Breeding Bird Survey and search query time series from Google Trends as indices of rodent numbers to investigate whether wood warbler respond to rodent outbreaks at a broad spatial scale. Additionally, we investigated whether population fluctuations of Eurasian Jay Garrulus glandarius, the important predator of wood warbler nests, negatively correlated with wood warbler densities and how rodent outbreaks may have affected the outcome of interactions between those species. Results suggested that in years with low rodent abundance, wood warblers avoided settling in areas with high densities of jays. However, when rodent abundance increased in response to masting, wood warblers switched settling strategy and exhibited nomadic behavior. Moreover, this phenomenon acts at a broad geographical scale, which is a unique feature for European forest-dwelling insectivorous. We proposed the hypothesis that wood warblers perceive different predators as unequal and exhibit a risk sensitive antipredator behavior in their habitat selection process. Such a sophisticated mechanism of avoiding predators would suggest that wood warblers are able to acquire information about predation risk, for example, by assessing rodent abundance and use this information to adjust settlement decisions appropriately.

ГЕОМЕТРИЧЕСКОЕ МОДЕЛИРОВАНИЕ ООЛОГИЧЕСКОЙ ВАРИАБЕЛЬНОСТИ У ВРАНОВЫХ ПТИЦ

We analyzed the egg shape in bird family Corvidae using a polynomial model and a compound ovoid model. We constructed a geometric model that reflects the relationship between cloacal and infundibular arcs, and the length and the diameter of the egg. Specifically, we quantified the shape of the egg via seven indices: the traditional index of elongation and six novel indices. Morphological parameters of bird eggs within three genera of Corvids (Corvus, Pica, and Garrulus) revealed that although there was overlap with their minimum and maximum values, the mean values remained different. Cluster analysis, using suggested indices and polynomial equations based on the absolute length and diameter of eggs, demonstrated different values within three main groups: the Hooded Crow, Carrion Crow, and Common Raven group, the European Jackdaw and Eurasian Jay group, and the Rook and Eurasian Magpie group. This is best explained by the variation in the elongation indices, suggesting that spheroid eggs are the optimal for clutches of 1-2 eggs or more than 5 eggs. Geometrical schemes, formulas of compound ovoid, and polynomial equations generated for seven species of corvids are supplied, which provide evidence of species-specific patterns of egg shapes.

The influence of road traffic on birds during autumn period: Implications for planning and management of road network

The main objective of this study was to assess disturbance to birds at stopover sites in the vicinity of roads. We attempted to determine the influence of a busy road on birds during the autumn migration period. To our knowledge this is the first study in Europe carried out during this part of a bird's annual cycle in the context of road noise impact. Individuals were counted using the point method at 36 observation points located at three distances (60m, 310m, 560m) from the road. At each point we determined the habitat parameters and the intensity of noise. In total, 648 individuals from 25 species were recorded on the study plot. The number of birds per point was higher on the second line of points but lower on the last line from the road. Species diversity was lower near the road. The density of the following common species increased with distance from the road: Eurasian jay, great spotted woodpecker, siskin, mistle thrush and nuthatch. Only great tits preferred the proximity of the road. The number and species diversity of birds were correlated with road noise propagation across our study area. Noise levels below 49dB did not significantly influence the number of birds or species richness. Our results showed that species foraging on invertebrates preferred the neighbourhood of the road. These data may be helpful in planning and managing road environments in the context of bird conservation and protection against road noise.

Predation and dispersal of acorns by European Jay (Garrulus glandarius) differs between a native (Pedunculate Oak Quercus robur) and an introduced oak species (Northern Red Oak Quercus rubra) in Europe

Invasive species have a substantial influence on the environment, especially through competition with local, native species. In Europe, oak trees provide a good example of competition between species native to the region and species introduced from elsewhere in the Northern Hemisphere. When introduced species start to have a negative impact they are considered invasive. Here we focus on the seed dispersal of a native (Pedunculate Oak Quercus robur) compared to an introduced oak (Northern Red Oak Quercus rubra) where the main animal disperser of acorns is the European Jay Garrulus glandarius. The study was conducted in two forests in western Poland by placing acorns of both species in trays and monitoring their removal, and by recording establishing oaks on transects. We showed that jays were about twice as likely to harvest the acorns of the native oak compared to those of the introduced oak. Nevertheless, the extent of dispersal by jays of the acorns of the introduced oak species will facilitate colonization of new areas. Establishment of young trees of the introduced species was much greater than that of the native species despite the former having lower dispersal and being considerably underrepresented in the canopy. Thus, consequences for patterns of oak survival and forest development seem very likely.

Surface texture and priming play important roles in predator recognition by the red-backed shrike in field experiments.

We compared the responses of the nesting red-backed shrikes (Lanius collurio) to three dummies of a common nest predator, the Eurasian jay (Garrulus glandarius), each made from a different material (stuffed, plush, and silicone). The shrikes performed defensive behaviour including attacks on all three dummies. Nevertheless, the number of attacks significantly decreased from the stuffed dummy through the plush dummy and finally to the silicone dummy. Our results show that wild birds use not only colours but also other surface features as important cues for recognition and categorization of other bird species. Moreover, the silicone dummy was attacked only when presented after the stuffed or plush dummy. Thus, we concluded that the shrikes recognized the jay only the stuffed (with feathered surface) and plush (with hairy surface) dummies during the first encounter. Recognition of the silicon dummy (with glossy surface) was facilitated by previous encounters with the more accurate model. This process resembles the effect of perceptual priming, which is widely described in the literature on humans.