At present, urban areas cover almost 3% of the Earth’s terrestrial area, and this proportion is constantly increasing. Although urbanization leads to a decline in biodiversity, at the same time it creates extensive habitats that are exploited by an assemblage of organisms, including birds. The species composition and density of birds nesting in towns and cities are determined by the types of buildings, the structure and maturity of urban greenery, and habitat diversity. In contrast, the habitat traits shaping the community of birds wintering in urban areas are not known. The aim of this work was to assess the influence of habitat structure, food resources and the urban effects (pollution, noise, artificial light) on an assemblage of birds overwintering in an urban area. It was carried out in 2014 and 2015 in the city of Kraków (southern Poland), on 56 randomly chosen sample plots, in which the composition, density and interseasonal similarity of bird assemblage were assessed with line transect method. A total of 64 bird species (mean = 17.7 ± 4.9 SD species/plot) was recorded. The mean density was 89.6 ind./km ±63.3 SD. The most numerous species were Great Tit Parus major, Magpie Pica pica, Blackbird Turdus merula, Blue Tit Cyanistes caeruleus, Rook Corvus frugilegus, Fieldfare Turdus pilaris and House Sparrow Passer domesticus. Noise adversely affected species numbers and density, but artificial light acted positively on the density of birds and their interseasonal stability. The species richness and density of birds were also determined by the number of food sources available (e.g. bird-feeders). In addition, the greater the proportion of open areas, the fewer species were recorded. In contrast, the more urban greenery there was, the greater the density of the entire bird assemblage. Urban infrastructure (buildings, roads, refuse tips) had a positive effect on the interseasonal stabilization of the species composition of wintering birds. The results of this work indicate that the urban effect, i.e. noise and light pollution, apart from purely habitat factors, provide a good explanation for the species richness, density and stability of bird assemblage wintering in urban areas.

Nocturnal avian migration flyways remain an elusive concept, as we have largely lacked methods to map their full extent. We used the network of European weather radars to investigate nocturnal bird movements at the scale of the European flyway. We mapped the main migration directions and showed the intensity of movement across part of Europe by extracting biological information from 70 weather radar stations from northern Scandinavia to Portugal, during the autumn migration season of 2016. On average, over the 20 nights and all sites, 389 birds passed per 1 km transect per hour. The night with highest migration intensity showed an average of 1621 birds km ^–1 h ^–1 passing the radar stations, but there was considerable geographical and temporal variation in migration intensity. The highest intensity of migration was seen in central France. The overall migration directions showed strong southwest components. Migration dynamics were strongly related to synoptic wind conditions. A wind‐related mass migration event occurred immediately after a change in wind conditions, but quickly diminished even when supporting winds continued to prevail. This first continental‐scale study using the European network of weather radars demonstrates the wealth of information available and its potential for investigating large‐scale bird movements, with consequences for ecosystem function, nutrient transfer, human and livestock health, and civil and military aviation.

Urban environments cover vast areas with a high density of humans and their dogs and cats causing problems for exploitation of new resources by wild animals. Such resources facilitate colonization by individuals with a high level of neophilia predicting that urban animals should show more neophilia than rural conspecifics. We provided bird-feeders across urban environments in 14 Polish cities and matched nearby rural habitats, testing whether the presence of a novel item (a brightly coloured green object made out of gum with a tuft of hair) differentially delayed arrival at feeders in rural compared to urban habitats. The presence of a novel object reduced the number of great tits Parus major, but also the total number of all species of birds although differentially so in urban compared to rural areas. That was the case independent of the potentially confounding effects of temperature, population density of birds and the abundance of cats, dogs and pedestrians. The number of great tits and the total number of birds attending feeders increased in urban compared to rural areas independent of local population density of birds. This implies that urban birds have high levels of neophilia allowing them to readily exploit unpredictable resources in urban environments.

Migratory animals provide a multitude of services and disservices—with benefits or costs in the order of billions of dollars annually. Monitoring, quantifying, and forecasting migrations across continents could assist diverse stakeholders in utilizing migrant services, reducing disservices, or mitigating human–wildlife conflicts. Radars are powerful tools for such monitoring as they can assess directional intensities, such as migration traffic rates, and biomass transported. Currently, however, most radar applications are local or small scale and therefore substantially limited in their ability to address large-scale phenomena. As weather radars are organized into continent-wide networks and also detect “biological targets,” they could routinely monitor aerial migrations over the relevant spatial scales and over the timescales required for detecting responses to environmental perturbations. To tap these unexploited resources, a concerted effort is needed among diverse fields of expertise and among stakeholders to recognize the value of the existing infrastructure and data beyond weather forecasting.

Although large and medium-sized herbivorous mammals avoid urbanized areas, they have recently begun to colonize towns and cities. In general, ungulates continue to avoid the centres of urban areas, and utilize mainly their thinly built-up outskirts. While extension of urban development is preventing ungulates from penetrating the urban landscape, the influence of noise and light pollution on the occurrence of mammalian herbivores is still poorly understood. Hence, we investigated the hypothesis that habitat availability shapes the distribution of roe deer Capreolus capreolus and artificial lightening discourages them from penetrating the urban landscape. Roe deer was recorded on 37% of randomly selected sample plots (N = 60) located within the city of Kraków (S Poland). The occupied plots contained significantly more open habitats, woodland patches were larger in them, but proximity to rivers, and noise and light pollution were significantly lower. The logistic regression model revealed that an increasing area of open habitats was positively correlated with the probability of roe deer occurring. However, the artificial lighting at night was negatively correlated with the probability of the species occurring: the negative effect of light pollution was mitigated by the greater area of open habitats. Our study highlights the very considerable potential of light pollution as a predictor of the occurrence of large mammals in the urban landscape. We argue that urbanization and the related artificial lighting at night may be a factor preventing ungulates from penetrating potentially suitable habitats in urban areas.