Global loss of avian evolutionary uniqueness in urban areas

Urbanization reduces diversity, simplifies community and filter bird species based on their functional traits in a tropical city

Understanding how organisms are coping with major changes imposed by urban intensification is a complex task. In fact, our understanding of the impacts of urbanization on biodiversity is scarce in the global south compared to the north. In this study, we evaluated how bird communities are affected by impact of urban intensification in a tropical city. Thus, we assessed whether increased urban intensification 1) jeopardizes bird diversity (taking into account taxonomic-TD, phylogenetic-PD, and functional-FD dimensions), 2) drives changes in bird community composition and enables the detection of indicator species of such impact, and 3) leads to changes in bird functional traits linked to reproduction, resource acquisition, and survival. We found that urban intensification has a direct impact on the bird community, reducing all three types of diversity. Communities in areas of greater urban intensity are represented by fewer species, and these species are PD and FD less distinct. In addition, we detected at least ten species of areas of lower urban intensity that proved to be more sensitive to urban intensification. With regard to bird traits, we found no significant responses from reproductive, habitat use and feeding variables. Body weight and tail length were the only variables with significant results, with higher urbanization intensity areas selecting for species with lower weights and longer tails. Given the global biodiversity loss we are observing, this information can guide urban managers and planners in designing urban landscapes to maintain biodiversity in cities.

Long-term population trends of 48 urban bird species correspond between urban and rural areas

Colonization of urban areas by wild species is a widespread phenomenon investigated from various ecological and evolutionary perspectives, yet long-term population trends of organisms in urban areas remain understudied. To fill this knowledge gap, we used data from a large-scale breeding bird monitoring scheme and computed population trends in 48 urban bird species in urban and rural areas of a central European country, Czechia. In most species, trends were similar in both environments, indicating common drivers and/or connections between urban and rural populations. In species with significant trends, the positive trends prevailed, suggesting good performance of urbanized species. This may result from wildlife-friendly environmental changes in cities, such as the expansion of green areas and the maturing of woody vegetation. In respect to species traits, more positive trends were found in larger species than in smaller species in both habitats, likely due to the recovery of previously depleted populations.

Birds of Berlin: Changes in communities and guilds in the urban park "Tiergarten" since 1850

Urbanization has far-reaching consequences on birds, and knowledge of the impacts on taxonomic and functional diversity is necessary to make cities as compatible as possible for species. Avian diversity in parks in urban centers has been investigated multiple times, but rarely so in long-term studies due to lacking data. The Tiergarten in Berlin is a large-scale park in the city center of great value for people and many species including birds. We compiled bird species lists since 1850 and from monitoring in 2022 in one dataset to investigate how bird communities and guilds have changed over time and how these alterations were influenced by the eventful history of the park's vegetation conditions. Long-term changes in species assemblages were analyzed with an ordination analysis, and changes in guild presence and functional richness were discussed with regard to landscape transitions. A gradual development of species assemblages yet only small changes in guild composition since 1850 was detected, whereas the 1950 community stands out with a drop in species richness and replacement of forest species with an open land community, which reflects the deforestation of the park during World War II. Consideration of habitat, lifestyle, trophic, and migration guilds revealed no sign of functional homogenization over the last 172 years (1850-2022). Despite the high frequentation of the park by humans it still allows for a high bird diversity due to the Tiergarten's sheer size and heterogeneity of vegetation and habitats. We recommend that the park is maintained and managed accordingly to preserve this condition and advise other urban parks to strive for these beneficial features.

Urbanization correlates with the prevalence and richness of blood parasites in Eurasian Blackbirds (Turdus merula)

Urbanization is increasing worldwide, producing severe environmental impacts. Biodiversity is affected by the expansion of cities, with many species being unable to cope with the different human-induced stressors present in these landscapes. However, this knowledge is mainly based on research from taxa such as plants or vertebrates, while other organisms like protozoa have been less studied in this context. The impact of urbanization on the transmission of vector-borne pathogens in wildlife is still unclear despite its relevance for animal and human health. Here, we investigated whether cities are associated with changes in the prevalence and richness of lineages of three vector-borne protozoans (Plasmodium, Haemoproteus and Leucocytozoon) in Eurasian blackbirds (Turdus merula) from multiple urban and forest areas in Europe. Our results show important species-specific differences between these two habitat types. We found a significant lower prevalence of Leucocytozoon in urban birds compared to forest birds, but no differences for Plasmodium and Haemoproteus. Furthermore, the richness of parasite lineages in European cities was higher for Plasmodium but lower for Leucocytozoon than in forests. We also found one Plasmodium lineage exclusively from cities while another of Leucocytozoon was only found in forests suggesting a certain level of habitat specialization for these protozoan vectors. Overall, our findings show that cities provide contrasting opportunities for the transmission of different vector-borne pathogens and generate new scenarios for the interactions between hosts, vectors and parasites.

Composition of soil mesofauna in changing cropping systems due to urbanization in Bengaluru, India

The study focused on the composition of soil mesofauna within changing cropping systems influenced by urbanization in Bengaluru, Karnataka, India during the rabi season of 2020 (October)-2021 (February). Four major cropping systems, namely pulses (red gram), vegetables (tomato and ridge gourd), horticulture (grapes and chickoo), and agriculture + horticulture crops, (coconut + fodder plantation), were examined across urban, peri-urban, and rural zones in Bengaluru. The research uncovered a total of 714 individuals belonging to 16 different soil mesofauna taxa among the crops studied. Collembolans were found to be the most abundant members of the mesofauna community, with mites following closely. In terms of population dynamics, the highest mesofauna population was observed in December 2020, totaling 248 individuals, while the lowest count was recorded in February 2021, with 104 individuals. Among the crops studied, the highest number of individuals was found in Horticulture systems, with 277 individuals, closely followed by the Agri + horticulture cropping system, which had 158 individuals. When considering the geographical zones, the highest number of individuals was recorded in the urban zones, with 270 individuals, followed by peri-urban areas with 229 individuals, and the rural zone had the lowest count, totaling 225 individuals. From the results, less disturbed soil environment in horticulture cropping system, post-monsoon conditions in December (2020), and the urban heat in urban zone appeared to favor the proliferation of soil mesofauna.

Urbanization drives biotic homogenization of the avian community in China

Urbanization-driven biotic homogenization has been recorded in various ecosystems on local and global scales; however, it is largely unexplored in developing countries. Empirical studies on different taxa and bioregions show conflicting results (i.e. biotic homogenization vs. biotic differentiation); the extent to which the community composition changes in response to anthropogenic disturbances and the factors governing this process, therefore, require elucidation. Here, we used a compiled database of 760 bird species in China to quantify the multiple-site β-diversity and fitted distance decay in pairwise β-diversities between natural and urban assemblages to assess whether urbanization had driven biotic homogenization. We used generalized dissimilarity models (GDM) to elucidate the roles of spatial and environmental factors in avian community dissimilarities before and after urbanization. The multiple-site β-diversities among urban assemblages were markedly lower than those among natural assemblages, and the distance decays in pairwise similarities in natural assemblages were more rapid. These results were consistent among taxonomic, phylogenetic, and functional aspects, supporting a general biotic homogenization driven by urbanization. The GDM results indicated that geographical distance and temperature were the dominant predictors of avian community dissimilarity. However, the contribution of geographical distance and climatic factors decreased in explaining compositional dissimilarities in urban assemblages. Geographical and environmental distances accounted for much lower variations in compositional dissimilarities in urban than in natural assemblages, implying a potential risk of uncertainty in model predictions under further climate change and anthropogenic disturbances. Our study concludes that taxonomic, phylogenetic, and functional dimensions elucidate urbanization-driven biotic homogenization in China.

Woody species composition, diversity, and ecosystem services of yards along an urban socioeconomic gradient

Woody plants offer a wide range of valuable ecosystem services, but their distribution across socioeconomic gradients in urban landscapes remains poorly understood. Thus, we explored the effect of socioeconomic and legacy factors on plant species richness and phylogenetic diversity, and the motivations for growing and keeping certain species. We sampled a total of 300 households across a socioeconomic gradient in the city of Harare, Zimbabwe, in high-, medium- and low-density areas, representing low to high wealth strata. Trees were mostly grown for ornamental purpose in the rich (low-density) suburbs and utilitarian purposes in the poorer medium to high-density areas. However, trees were also grown with similar proportion for shade across the socioeconomic gradient. Proportion of medicinal and fruit trees increased with household density, while wind break trees were more common in low-density suburbs. Exotic species exhibited greater species richness compared with indigenous species, with both combined and separate assessments of indigenous and exotic species richness revealing a significant positive association with socioeconomic and legacy factors. The composition of species displayed considerable variation along the socioeconomic gradient. Notably, in low-density environments, exotic species maintained elevated phylogenetic diversity in comparison to indigenous species. This distinction was particularly pronounced when analysed independently, revealing a significant positive correlation between exotic species richness and both property value and education level. Our study shows that residents filter specific plant species based on their socioeconomic status and that, relative to low-income households, the rich homeowners have unintentionally incorporated enough exotic species to produce novel phylogenetic diversity of woody plants in their yards. Thus, we confirm the existence of a socioeconomic gradient in terms of species richness, composition, and phylogenetic diversity. However, the imbalance in species richness and phylogenetic diversity across the socioeconomic gradient can be reduced by increased tree planting in open areas, including along streets in medium to high-density areas to improve ecosystem services.

Dense city centers support less evolutionary unique bird communities than sparser urban areas

Urbanization alters avian communities, generally lowering the number of species and contemporaneously increasing their functional relatedness, leading to biotic homogenization. Urbanization can also negatively affect the phylogenetic diversity of species assemblages, potentially decreasing their evolutionary distinctiveness. We compare species assemblages in a gradient of building density in seventeen European cities to test whether the evolutionary distinctiveness of communities is shaped by the degree of urbanization. We found a significant decline in the evolutionary uniqueness of avian communities in highly dense urban areas, compared to low and medium-dense areas. Overall, communities from dense city centers supported one million years of evolutionary history less than communities from low-dense urban areas. Such evolutionary homogenization was due to a filtering process of the most evolutionarily unique birds. Metrics related to evolutionary uniqueness have to play a role when assessing the effects of urbanization and can be used to identify local conservation priorities.

Geographic variations in eco-evolutionary factors governing urban birds: The case of university campuses in China

Urbanization alters natural habitats, restructures biotic communities and serves as a filter for selecting species from regional species pools. However, empirical evidence of the specific traits that allow species to persist in urban areas yields mixed results. More importantly, it remains unclear which traits are widespread for species utilizing urban spaces (urban utilizers) and which are environment-dependent traits. Using 745 bird species from 287 university/institute campuses in 74 cities and their species pools across China, we tested whether species that occur in urban areas are correlated with regards to their biological (body mass, beak shape, flight capacity and clutch size), ecological (diet diversity, niche width and habitat breadth), behavioural (foraging innovation) and evolutionary (diversification rate) attributes. We used Bayesian phylogenetic generalized linear mixed models to disentangle the relative roles of these predictors further, and to determine the extent to which the effects of these predictors varied among different cities. We found that urban birds were more phylogenetically clustered than expected by chance, and were generally characterized by a larger habitat breadth, faster diversification rate, more behavioural innovation and smaller body size. Notably, the relative effects of the attributes in explaining urban bird communities varied with city temperature and elevation, indicating that the filters used to determine urban species were environment dependent. We conclude that, while urban birds are typically small-sized, generalists, innovative and rapidly diversifying, the key traits that allow them to thrive vary spatially, depending on the climatic and topographic conditions of the city. These findings emphasize the importance of studying species communities within specific cities to better understand the contextual dependencies of key traits that are filtered by urban environments.

Urban greenspaces shape soil protist communities in a location-specific manner

The impacts of urbanization on aboveground biodiversity are well studied, and its impact on soil microorganisms are also receiving increased attention. However, the impact of urbanization on the soil protists are hardly investigated. Here, we studied how urbanization and distinct urban greenspaces affect protist communities. We used amplicon sequencing of the18 S rRNA gene of samples from five types of urban greenspaces (parks, greenbelts, industrial areas, residential areas and hospital lawns), neighboring natural forests and agricultural ecosystems in Ningbo, China. We found that urban greenspaces harbored higher protist α-diversity than forests, while protist β-diversity increased from agricultural systems to urban greenspaces to forests. Among the studied driving factors, soil bacterial α- and β-diversity best predicted phagotrophic protist α- and β-diversity in urban greenspaces, while differences in α- and β-diversity of phototrophic protists were best explained by soil carbon-to-nitrogen ratio and fungal β-diversity, respectively. Abiotic factors i.e., total phosphorus and carbon-to-nitrogen ratio, best predicted the α- and β-diversity of protist parasites in urban greenspaces, respectively. The results revealed that the composition and drivers of protist communities vary between functional groups and urban ecosystems. Overall, our findings contribute to a better understanding of drivers of soil protist communities and indicate that soil protist communities and associated soil functions could be managed in predictable ways in urban greenspaces.

A potential consequence for urban birds' fitness: Exposed anthropogenic nest materials reduce nest survival in the clay-colored thrush

Urban bird dwellers survive and reproduce in highly urbanized ecosystems. Some individuals adjust to these novel conditions by changing natural nesting materials for artificial materials, thus making nests more conspicuous in the environment. The consequences of using artificial materials for nesting remain poorly understood, especially from a nest-predator perspective. We studied if exposed artificial materials on bird nests affect the daily survival rate in a common dweller species, the clay-colored thrush (Turdus grayi). We used previously collected nests with a different area of exposed artificial materials and placed them with clay eggs on the main campus of the Universidad de Costa Rica. During 12 days of the reproductive season, we monitored the nests using trap cameras located in front of each nest. We found that nest survival decreased as the proportion of exposed artificial materials increased in the nest and, unexpectedly, that the principal predators were conspecifics. Thus, artificial materials used in the outer layer of nests make them more susceptible to predation. The use of artificial materials likely reduce reproductive success and population size in urban clay-colored thrush, but further field experiments measuring the effect of waste in birds' nests on the reproductive success of urban birds are needed.

Lockdown effects on fear revealed direct and indirect effects of human presence on perceived predation risk

The Covid-19 lockdown reduced drastically human presence outdoors, providing an uncontrolled experiment for disentangling direct and indirect effects of human presence on animal fearfulness. We measured 18,494 flight initiation distances (FIDs, the distance at which individual animals fly away when approached by a human) from 1333 populations of 202 bird species taken in four European cities both before, during and after the lockdown. FIDs decreased during lockdown in rural habitats but increased in urban habitats, especially for singing birds. Height above ground increases during lockdown in non-singing birds only, and birds adjusted horizontal tolerance to approach according to height outside lockdown, in rural habitats and while not singing. Responses showed lagged effects after lockdown in urban but not in rural habitats. Differential responses to lockdown among habitats and between signing and non-singing birds were consistent with relaxation of direct disturbance effects on birds in rural habitats during lockdown, as well as with increased indirect fear effects mediated by predator release in cities. FIDs seemed to measure the balance of direct and indirect effects of humans on predations risk and food needs rather than direct effects of humans on fear.

EVI and NDVI as proxies for multifaceted avian diversity in urban areas

Most ecological studies use remote sensing to analyze broad-scale biodiversity patterns, focusing mainly on taxonomic diversity in natural landscapes. One of the most important effects of high levels of urbanization is species loss (i.e., biotic homogenization). Therefore, cost-effective and more efficient methods to monitor biological communities' distribution are essential. This study explores whether the Enhanced Vegetation Index (EVI) and the Normalized Difference Vegetation Index (NDVI) can predict multifaceted avian diversity, urban tolerance, and specialization in urban landscapes. We sampled bird communities among 15 European cities and extracted Landsat 30-meter resolution EVI and NDVI values of the pixels within a 50-m buffer of bird sample points using Google Earth Engine (32-day Landsat 8 Collection Tier 1). Mixed models were used to find the best associations of EVI and NDVI, predicting multiple avian diversity facets: Taxonomic diversity, functional diversity, phylogenetic diversity, specialization levels, and urban tolerance. A total of 113 bird species across 15 cities from 10 different European countries were detected. EVI mean was the best predictor for foraging substrate specialization. NDVI mean was the best predictor for most avian diversity facets: taxonomic diversity, functional richness and evenness, phylogenetic diversity, phylogenetic species variability, community evolutionary distinctiveness, urban tolerance, diet foraging behavior, and habitat richness specialists. Finally, EVI and NDVI standard deviation were not the best predictors for any avian diversity facets studied. Our findings expand previous knowledge about EVI and NDVI as surrogates of avian diversity at a continental scale. Considering the European Commission's proposal for a Nature Restoration Law calling for expanding green urban space areas by 2050, we propose NDVI as a proxy of multiple facets of avian diversity to efficiently monitor bird community responses to land use changes in the cities.

Effects of light and noise pollution on avian communities of European cities are correlated with the species' diet

Urbanization affects avian community composition in European cities, increasing biotic homogenization. Anthropic pollution (such as light at night and noise) is among the most important drivers shaping bird use in urban areas, where bird species are mainly attracted by urban greenery. In this study, we collected data on 127 breeding bird species at 1349 point counts distributed along a gradient of urbanization in fourteen different European cities. The main aim was to explore the effects of anthropic pollution and city characteristics, on shaping the avian communities, regarding species' diet composition. The green cover of urban areas increased the number of insectivorous and omnivorous bird species, while slightly decreasing the overall diet heterogeneity of the avian communities. The green heterogeneity-a measure of evenness considering the relative coverage of grass, shrubs and trees-was positively correlated with the richness of granivorous, insectivorous, and omnivorous species, increasing the level of diet heterogeneity in the assemblages. Additionally, the effects of light pollution on avian communities were associated with the species' diet. Overall, light pollution negatively affected insectivorous and omnivorous bird species while not affecting granivorous species. The noise pollution, in contrast, was not significantly associated with changes in species assemblages. Our results offer some tips to urban planners, managers, and ecologists, in the challenge of producing more eco-friendly cities for the future.

From headwaters to outlets: Bird species accrual curves are faster downstream with different implications for varying landcovers and ecoregions

Terrestrial and aquatic systems are geographically connected, yet these systems are typically studied independently of each other. This approach omits a large amount of ecological information as landscapes are best described as mosaics in watersheds. Species Accumulation Curves (SACs) that incorporate sampling effort are familiar models of how biodiversity will change when landcovers are lost. In land-based systems, the consistent pattern of increased species richness with increasing number of sites sampled is an ecological norm. In freshwater systems, fish species discharge relationships are analogous to species-area relationships in terrestrial systems, but the relationship between terrestrial species and discharge remains largely unexplored. Although some studies investigate the effect of terrestrial systems on neighboring aquatic species, less work has been done on exploring the effect of aquatic systems on terrestrial species. Additionally, creating statistical models to observe these interactions need to be explored further. Using data from the Ontario Breeding Bird Atlas (2001–2005), we created bird SACs to explore how increases in diversity with sites sampled varies with watershed position on the Canadian side of the Great Lakes Basin (GLB). The mosaic landscape of the GLB was characterized using six majority land cover classes at a 15 m resolution. This work shows that rates of species accrual and potential maximum species richness vary as a function of watershed position, underlying land cover, and the Ecoregion in which sampling was performed. We also found that Urban landcover has the potential to retain relatively high levels of species richness, which is further modified by Ecoregion and watershed position. Through our ‘world building,’ we believe that we can increase knowledge around the importance of land-water interactions and further the goals of viewing landscapes as mosaic watersheds.

Urban biotic homogenization: Approaches and knowledge gaps

Urbanization is restructuring ecosystems at an unprecedented pace, with complex and profound consequences for life on Earth. One of the hypothesized trajectories of urban ecosystems and species communities is biotic homogenization, possibly leading to very similar species assemblages in cities across the globe. Urbanization can, however, also have the opposite effect: biotic diversification, with cities, at least at the local scale, becoming biologically more diverse, mainly as a consequence of high species introduction rates and habitat diversification. Applying the hierarchy-of-hypotheses approach, we systematically map and structure the comprehensive body of literature on the urban biotic homogenization (UBH) hypothesis, comprising 225 individual studies (i.e., tests of the hypothesis) retrieved from 145 publications. The UBH hypothesis is studied at multiple levels with a multitude of approaches and underlying assumptions. We show that UBH is generally used with two very different connotations: about half of the studies investigated a potential increase in community similarity across cities, whereas the other half investigated biotic homogenization within cities, the latter being supported more frequently. We also found strong research biases: (1) a taxonomic bias towards birds and plants, (2) a bias towards small and medium distances (<5000 km) in comparisons across cities, (3) a dominance of studies substituting space for time versus true temporal studies, (4) a strong focus on terrestrial versus aquatic systems, (5) more extraurban (including periurban) areas than natural or rural ecosystems for comparison to urban systems, (6) a bias towards taxonomic versus functional, phylogenetic, and temporal homogenization, and (7) more studies undertaken in Europe and North America than in other continents. The overall level of empirical support for the UBH hypothesis was mixed, with 55% of the studies reporting supporting evidence. Results significantly differed when a natural/nature reserve, an extraurban, or rural/agricultural area served as reference to infer biotic homogenization, with homogenization being detected least frequently when urban systems were compared to agricultural, i.e., other anthropogenically influenced, study sites. We provide an evidence map and a bibliographic network and identify key references on UBH with the goal to enhance accessibility and orientation for future research on this topic.

Effects of urbanization on woody plant phylogenetic diversity and its associations with landscape features in the high latitude northern hemisphere region, Northeast China

Urbanization is one of the primary drivers of terrestrial modification, with marked biological homogenization worldwide but relatively poor knowledge of woody phylogenetic diversity. Here, we investigated 943 plots, about 93,000 woody plants from 130 species in Northeast China, and calculated six phylogenetic diversity indexes, and urbanization landscape metrics; the responses of phylogenetic diversity to urbanization and its coupling relationship with landscape features were explored at 25 km × 25 km, 50 km × 50 km and 75 km × 75 km grid scales. We found that urbanization had enhanced the evolutionary distinctiveness of woody plants, characterizing as increasing Faith phylogenetic diversity (FPD) and their mean pairwise distance (MPD) while decreasing the mean nearest taxon distance (MNTD); these trends were independent of landscape scales and gymnosperm inclusion or not. As indicated by increasing SesMPD (Standardized MPD), the dominant role of community assemblage changed from environmental filtering in low urbanization intensity (UI) to competitive exclusion in high UI regions. Artificial surface area (ASA) and its percentage, SHAPE_F (Shape index of forest), and PD_F (Patch density of forest) had a threshold effect on phylogenetic diversity. ASA%, GDP (gross domestic product), and population density were the most potent predictors for the variations of phylogenetic diversity, and GDP contributed the most (42.9%). A higher GDP accompanied a higher FPD, SesPD (Standardized FPD), and SesMNTD (Standardized MNTD); higher PD_F and lower SHAPE_F were associated with higher MNTD, MPD, and SesMPD. In conclusion, urbanization strongly modifies woody plant phylogenetic diversity. Identifying the threshold effects and significant factors for phylogenetic variations allows biodiversity assessment and conservation through proper landscape configuration under the urbanization context.

Bird lineages colonizing urban habitats have diversified at high rates across deep time

AIM

Urbanization exposes species to novel ecological conditions. Some species thrive in urban areas, whereas many others are excluded from these human-made environments. Previous analyses suggest that the ability to cope with rapid environmental change is associated with long-term patterns of diversification, but whether the suite of traits associated with the ability to colonize urban environments is linked to this process remains poorly understood.

LOCATION

World.

TIME PERIOD

Current.

MAJOR TAXA STUDIED

Passerine birds.

METHODS

We applied macroevolutionary models to a large dataset of passerine birds to compare the evolutionary history of urban-tolerant species with that of urban-avoidant species. Specifically, we examined models of state-dependent speciation and extinction to assess the macroevolution of urban tolerance as a binary trait, in addition to models of quantitative trait-dependent diversification based on relative urban abundance. We also ran simulation-based model assessments to explore potential sources of bias.

RESULTS

We provide evidence that historically, species with traits promoting urban colonization have undergone faster diversification than urban-avoidant species, indicating that urbanization favours clades with a historical tendency towards rapid speciation or reduced extinction. In addition, we find that past transitions towards states that currently impede urban colonization by passerines have been more frequent than in the opposite direction. Furthermore, we find a portion of urban-avoidant passerines to be recent and to undergo fast diversification. All highly supported models give this result consistently.

MAIN CONCLUSIONS

Urbanization is mainly associated with the loss of lineages that are inherently more vulnerable to extinction over deep time, whereas cities tend to be colonized by less vulnerable lineages, for which urbanization might be neutral or positive in terms of longer-term diversification. Urban avoidance is associated with high rates of recent diversification for some clades occurring in regions with relatively intact natural ecosystems and low current levels of urbanization.

The Good, the Bad, and the Ugly of Urbanization: Response of a Bird Community in the Neotropical Andes

Urbanization constitutes one of the most aggressive drivers of habitat and biodiversity loss worldwide. However, studies focused on determining the response of local biodiversity to urbanization are still scarce, especially in tropical ecosystems. Urban ecosystems are characterized by low biological productivity which in turn leads to a reduction in biodiversity. However, the responses to urbanization should be species dependent. For instance, changes in the availability of resources can favor certain species with specific characteristics. We assessed the effects of the urbanization process on a bird community in a city located in the Tropical Andes of southern Ecuador, a region widely recognized for its diversity and endemism of birds. We selected three independent localities in each of the four levels of the urbanization gradient in the study area (forest, forest-pasture, pasture, and urban). In each locality, we sampled the bird community by visual and auditory surveys along 1 km transects between 2016 and 2017. We recorded a total of 1,257 individuals belonging to 74 bird species. We evaluated if the responses of richness and abundance of birds are dependent on trophic guild and foraging strata. We found a significant decrease in bird species richness and abundance from forest to urban sites. However, the response of birds was dependent on the trophic guild and foraging strata. Granivorous birds showed a positive response associated with the urbanization gradient while insectivorous birds showed a negative response. Insectivorous birds were more abundant in forest sites and decreased in abundance across the urbanization gradient. We found that the proportion of birds using different foraging strata drastically changed along urban gradient. Forest sites exhibited a bird community using a variety of habitats, but the bird community became simpler toward the most urbanized sites. Our findings showed different effects of urbanization on bird communities. The ugly: urbanization leads to a dramatic reduction in the diversity of birds, which is consistent in cities with different characteristics and ecological contexts. On the other hand, the responses of bird guilds to urbanization are species dependent. Some guilds are positively impacted by urbanization and show increases in species richness and abundance while other guilds are negatively impacted.

Data from public and governmental databases show that a large proportion of the regional animal species pool occur in cities in Germany

Cities have been shown to be biodiverse, but it is unclear what fraction of a regional species pool can live within city borders and how this differs between taxa. Among animals, most research has focused on a few well-studied taxa, such as birds or butterflies. For other species, progress is limited by the paucity of data. We used species occurrence data for 11 taxa and 23 German cities from the Global Biodiversity Information Facility (GBIF) and the different German states, in a 50-km buffer around the city centre, to investigate what proportion of species of the regional species pools also occur in cities. While data could be obtained for all cities from GBIF, state databases only provided data for a subset of cities. Sample coverage of data from GBIF was higher across all taxa than of the state databases. For each database and taxon, we analysed (i) all cities where the number of occurrences of a taxon was &gt;50 and (ii) only those cities where additionally sample coverage was &gt;0.85. Across all taxa studied on average, 44.9 ± 7.2% (GBIF) and 40.8 ± 9.6% (German states) of the species of the regional species pool were also found in cities. When all cities were considered together, more than 76% of all species occurred within city borders. Our results show that German cities harbour a large part of the regional diversity of different taxa when city borders rather than the city centre is considered. This opens up ample opportunities for conservation and for fostering human–nature relationships.

Inconsistent Patterns of Soil Fauna Biodiversity and Soil Physicochemical Characteristic Along an Urbanization Gradient

Urbanization has induced substantial changes in soil physicochemical characteristic, which plays an important role in regulating soil fauna biodiversity in forests and grasslands. However, less is known about the urbanization effect on soil fauna biodiversity and how soil physicochemical changes mediate this effect. Along an urbanization gradient in the city of Guangzhou, we established four sites with different urbanization intensities, including an urban site, two suburban sites, and a rural site, and then studied their soil physicochemical characteristic and soil fauna biodiversity. The soil physicochemical characteristic dramatically changed along the urbanization gradient. In contrast, the soil fauna biodiversity exhibited a very different pattern. Soil fauna abundance was highest in the suburban sites. Moreover, there were significant changes of Pielou’s evenness and community structure in the suburban sites. Soil fauna biodiversity property in the urban site was similar to that in the rural site, except that the rural site was characterized by Enchytraeidae while the urban site was not characterized by any taxa. Our linear and canonical correspondence analysis models suggested that soil physicochemical characteristic only contributed a little to the variance of soil fauna abundance (19%), taxa number (27%), and community structure (12%). In contrast, soil physicochemical characteristic explained about half of the variance in Shannon’s diversity and Pielou’s evenness. However, with urbanization intensity increasing, soil physicochemical changes could both increase and decrease the diversity and evenness. Thus, our results revealed an inconsistent pattern between soil fauna biodiversity and soil physicochemical characteristic along an urbanization gradient. This study suggested that soil physicochemical change was less important as expected in regulating soil fauna biodiversity pattern under an urbanization context. To elucidate the effect of urbanization on soil fauna biodiversity, further studies should take other urbanization agents into account.

Human-wildlife interactions: presence of the ground-nesting Spotted Thick-knee across a South African mosaic urban landscape

Urbanisation has increasingly encroached on numerous bird species' natural habitats, generally negatively affecting their persistence. Furthermore, increased human-wildlife interactions may benefit or be detrimental to the long term persistence of these species. The Spotted Thick-knee (Burhinus capensis), a ground-nesting species, persists in some mosaic urban landscapes in South Africa. We, therefore, assessed the presence of Spotted Thick-knees and their interactions with humans in the fragmented natural and human-modified landscape of Pietermaritzburg, KwaZulu-Natal. We conducted presence-only surveys at 52 locations between July 2019 and December 2020. 'Presence' locations for Spotted Thick-knee were identified via active surveying and public participation. Newspaper articles were distributed in June 2019, requesting information on Spotted Thick-knee sightings. Questionnaires were also sent to respondents to collect qualitative information regarding their perceptions and observations of this species in Pietermaritzburg. We established that the presence of Spotted Thick-knee's at known locations was not random. They were present at 30 out of 52 sites for 75% of this study's duration. Fewer sites had Spotted Thick-knees present during non-breeding months than breeding months. Respondents' feedback highlighted the pressures associated with Spotted Thick-knees persistence in human-modified mosaic landscapes, particularly predation and disturbance by domestic pets. Our study highlights that some ground-nesting birds, such as Spotted Thick-knees, persist in mosaic urban landscapes, despite the anthropogenic pressures. This study highlights the need to address the paucity of studies on ground-nesting birds in mosaic urban landscapes to determine general trends.

Supplementary information

The online version contains supplementary material available at 10.1007/s11252-022-01254-3.

Residential yard management and landscape cover affect urban bird community diversity across the continental USA

Urbanization has a homogenizing effect on biodiversity and leads to communities with fewer native species and lower conservation value. However, few studies have explored whether or how land management by urban residents can ameliorate the deleterious effects of this homogenization on species composition. We tested the effects of local (land management) and neighborhood-scale (impervious surface and tree canopy cover) features on breeding bird diversity in six US metropolitan areas that differ in regional species pools and climate. We used a Bayesian multiregion community model to assess differences in species richness, functional guild richness, community turnover, population vulnerability, and public interest in each bird community in six land management types: two natural area park types (separate and adjacent to residential areas), two yard types with conservation features (wildlife-certified and water conservation) and two lawn-dominated yard types (high- and low-fertilizer application), and surrounding neighborhood-scale features. Species richness was higher in yards compared with parks; however, parks supported communities with high conservation scores while yards supported species of high public interest. Bird communities in all land management types were composed of primarily native species. Within yard types, species richness was strongly and positively associated with neighborhood-scale tree canopy cover and negatively associated with impervious surface. At a continental scale, community turnover between cities was lowest in yards and highest in parks. Within cities, however, turnover was lowest in high-fertilizer yards and highest in wildlife-certified yards and parks. Our results demonstrate that, across regions, preserving natural areas, minimizing impervious surfaces and increasing tree canopy are essential strategies to conserve regionally important species. However, yards, especially those managed for wildlife support diverse, heterogeneous bird communities with high public interest and potential to support species of conservation concern. Management approaches that include the preservation of protected parks, encourage wildlife-friendly yards and acknowledge how public interest in local birds can advance successful conservation in American residential landscapes.

Effects of urbanization on taxonomic, functional and phylogenetic avian diversity in Europe

Europe is an urbanized continent characterized by a long history of human-wildlife interactions. This study aimed to assess the effects of specific elements of urbanization and urban pollution on complementary avian diversity metrics, to provide new insights on the conservation of urban birds. Our study recorded 133 bird species at 1624 point counts uniformly distributed in seventeen different European cities. Our results thus covered a large spatial scale, confirming both effects of geographical and local attributes of the cities on avian diversity. However, we found contrasting effects for the different diversity components analyzed. Overall, taxonomic diversity (bird species richness), phylogenetic diversity and relatedness were significantly and negatively associated with latitude, while functional dispersion of communities showed no association whatsoever. At the local level (within the city), we found that urban greenery (grass, bush, and trees) is positively correlated with the number of breeding bird species, while the building cover showed a detrimental effect. Functional dispersion was the less affected diversity metric, while grass and trees and water (rivers or urban streams) positively affected the phylogenetic diversity of avian communities. Finally, the phylogenetic relatedness of species increased with all the main indicators of urbanization (building surface, floors, pedestrian's density and level of light pollution) and was only mitigated by the presence of bushes. We argue that maintaining adequate levels of avian diversity within the urban settlements can help to increase the potential resilience of urban ecosystems exposed to the stress provoked by rapid and continuous changes. We listed some characteristics of the cities providing positive and negative effects on each facet of urban avian diversity.

Contrasting effects of the COVID-19 lockdown on urban birds' reproductive success in two cities

The ubiquitous activity of humans is a fundamental feature of urban environments affecting local wildlife in several ways. Testing the influence of human disturbance would ideally need experimental approach, however, in cities, this is challenging at relevant spatial and temporal scales. Thus, to better understand the ecological effects of human activity, we exploited the opportunity that the city-wide lockdowns due to the COVID-19 pandemic provided during the spring of 2020. We assessed changes in reproductive success of great tits (Parus major) at two urban habitats affected strikingly differently by the ‘anthropause’, and at an unaffected forest site. Our results do not support that urban great tits benefited from reduced human mobility during the lockdown. First, at one of our urban sites, the strongly (− 44%) reduced human disturbance in 2020 (compared to a long-term reference period) did not increase birds’ reproductive output relative to the forest habitat where human disturbance was low in all years. Second, in the other urban habitat, recreational human activity considerably increased (+ 40%) during the lockdown and this was associated with strongly reduced nestling body size compared to the pre-COVID reference year. Analyses of other environmental factors (meteorological conditions, lockdown-induced changes in air pollution) suggest that these are not likely to explain our results. Our study supports that intensified human disturbance can have adverse fitness consequences in urban populations. It also highlights that a few months of ‘anthropause’ is not enough to counterweight the detrimental impacts of urbanization on local wildlife populations.

Long-term trends in the phylogenetic and functional diversity of Anatidae in South China coastal wetlands

Species loss has attracted much attention among scientists for more than half a century. However, we have little information on the trends in phylogenetic and functional changes behind the species loss although this information is always asynchronous and important for conservation and management. We measured community trends in Anatidae (ducks and geese) for the last 50 yr to quantify trends in phylogenetic and functional diversity patterns coinciding with taxonomic historical dynamics. We used one-way ANOVAs to test if there was a significant historical trend in communities of Anatidae. We characterized taxonomic, phylogenetic, and functional diversity of communities. For taxonomic diversity, we used species richness (SR). For phylogenetic diversity, we calculated the standardized effect size of mean pairwise distances (ses.MPD) and the standard effect size of mean nearest taxon distances (ses.MNTD) in communities. For functional diversity, we calculated functional richness (FRic), functional evenness (FEve), functional divergence (FDiv), and the community-level weighted means (CWM) of trait values for diet, foraging stratum, and body mass, separately. From the 1950s to 2010s, species richness declined without significant trends. The ses.MNTD of Anatidae communities showed no clear trends. However, ses.MPD of Anatidae communities declined dramatically during this period. For functional diversity, functional evenness of diet, foraging stratum, body mass, and functional dispersion of diet, foraging stratum did not increase or decline significantly. However, functional evenness of all traits, functional richness, and functional dispersion of body mass showed declined trends. The basic phylogenetic diversity and species body mass of Anatidae communities declined significantly because of a declining trend in the relative independent branch of geese. This makes it more challenging for implement community recovery in the future. More attention in conservation biology should consider taxonomic diversity and asynchrony in phylogenetic and functional diversity.

What is known - and not known - about acoustic communication in an urban soundscape

Urban environments have some of the most highly modified soundscapes on the planet, affecting the way many animals communicate using acoustic signals. Communication involves transmission of information via signals, such as bird song, between a signaler and a receiver. Much work has focused on the effects of urbanization on signalers and their signals, yet very little is known about how noise pollution affects receiver behaviors and sensory systems. Here we synthesize key findings to date regarding avian acoustic communication in the urban environment and delineate key gaps in knowledge for future work. We leverage our own work comparing current and historical songs from urban and rural habitats for a subspecies of white-crowned sparrows (Zonotrichia leucophrys nuttalli). We use this system, along with findings from other systems, to answer three key questions in the field: (1) Is song variation consistent with temporal and spatial variation in anthropogenic noise? (2) How are birds adjusting their song to the urban environment? and (3) How does song 'urbanization' affect signal function? Our synthesis illustrates that the adjustments birds make to their songs in noisy environments can improve signal detection, but potentially at the cost of signal function. Many key gaps in knowledge need to be addressed to complete our understanding of how acoustic communication systems evolve in urban areas, specifically in regard to sexual selection and female preference, as well as how receivers perceive signals in an urban environment.

Effects of Landscape Attributes on Campuses Bird Species Richness and Diversity, Implications for Eco-Friendly Urban Planning

Landscape changes due to urban expansion may severely influence urban biodiversity through direct and indirect effects. Hence, a comprehensive understanding of the urban expansion effects on species diversity is essential for conservation biologists, urban planners, and policymakers to help design more practical and effective conservation strategies. Here, based on monthly bird survey data of 12 university campuses distributed in the center and the Xianlin university town of Nanjing city, we first compared the differences of the campuses bird species richness, Shannon-Wiener, and Simpson indices. Then, we analyzed the effects of a variety of landscape attributes on the campuses bird species richness. Unlike other studies, we also constructed a 2 km buffer area surrounding each campus and analyzed the effects of the landscape attributes of the buffer area on species richness. We found that bird species richness was higher in the campus of Xianlin compared to those in the center. Landscape attributes played an important role on bird species richness, especially for the determinants in the buffer area. Specifically, species richness, Shannon-Wiener, and Simpson indices increased with the increasing area of water and green space both within the campus and the buffer area. Not surprisingly, bird species richness and diversity were more affected by fragmentation of the buffer area, increasing with the aggregation index and decreasing with the splitting index. Our study emphasized that landscape attributes of both campuses and buffer areas determined bird species richness and diversity, offering several practical implications for urban biodiversity maintenance and eco-friendly urban planning.

Urban green spaces in Dhaka, Bangladesh, harbour nearly half the country’s butterfly diversity

Cities currently harbour more than half of the world’s human population and continued urban expansion replaces natural landscapes and increases habitat fragmentation. The impacts of urbanisation on biodiversity have been extensively studied in some parts of the world, but there is limited information from South Asia, despite the rapid expansion of cities in the region. Here, we present the results of monthly surveys of butterflies in three urban parks in Dhaka city, Bangladesh, over a 3-year period (January 2014 to December 2016). We recorded 45% (137 of the 305 species) of the country’s butterfly richness, and 40% of the species detected are listed as nationally threatened. However, butterfly species richness declined rapidly in the three study areas over the 3-year period, and the decline appeared to be more severe among threatened species. We developed linear mixed effect models to assess the relationship between climatic variables and butterfly species richness. Overall, species richness was positively associated with maximum temperature and negatively with mean relative humidity and saturation deficit. Our results demonstrate the importance of urban green spaces for nationally threatened butterflies. With rapidly declining urban green spaces in Dhaka and other South Asian cities, we are likely to lose refuges for threatened fauna. There is an urgent need to understand urban biodiversity dynamics in the region, and for proactive management of urban green spaces to protect butterflies in South Asia.

Seasonal variation in the effects of artificial light at night on the occurrence of nocturnally migrating birds in urban areas

Urban areas often contain large numbers of migratory bird species during seasonal migration, many of which are nocturnal migrants. How artificial light at night (ALAN) and urban landcover are associated with the diurnal occurrence of nocturnal migrants within urban areas across seasons has not been explored. Here, we use eBird bird occurrence information to estimate the seasonal species richness of nocturnally migrating passerines (NMP) within 333 well surveyed urban areas within the contiguous USA. We model the relationship between seasonal NMP species richness and ALAN, proportion of tree canopy cover, and proportion of impervious surface. NMP species richness reached its highest levels during spring and autumn migration and lowest during the winter and summer. Greater tree canopy cover was associated with higher NMP species richness during spring and autumn migration and the summer. A 10% increase in the proportion of tree canopy cover was associated with a 2.0% increase in NMP species richness during spring migration, a 1.8% increase during autumn migration, and a 0.9% increase during the summer. More impervious surface was associated with higher NMP species richness during the winter. A 10% increase in the proportion of impervious surface was associated with a 6.1-9.8% increase in NMP species richness. Higher ALAN was associated with lower NMP species richness during the winter and summer, and higher NMP species richness during spring and autumn migration. A 50% increase in ALAN was associated with a 3.0-3.6% decrease in NMP species richness during the winter, a 1.7% increase during spring migration, a 2.1% decrease during the summer, and a 5.0% increase during autumn migration. These findings highlight the variable effects of ALAN and urban landcover on the seasonal occurrence of NMP species in urban areas, the value of tree canopy cover during migration and the breeding season, and the importance of reducing ALAN during migration.

Which Traits Influence Bird Survival in the City? A Review

Urbanization poses a major threat to biodiversity worldwide. We focused on birds as a well-studied taxon of interest, in order to review literature on traits that influence responses to urbanization. We review 226 papers that were published between 1979 and 2020, and aggregate information on five major groups of traits that have been widely studied: ecological traits, life history, physiology, behavior and genetic traits. Some robust findings on trait changes in individual species as well as bird communities emerge. A lack of specific food and shelter resources has led to the urban bird community being dominated by generalist species, while specialist species show decline. Urbanized birds differ in the behavioral traits, showing an increase in song frequency and amplitude, and bolder behavior, as compared to rural populations of the same species. Differential food resources and predatory pressure results in changes in life history traits, including prolonged breeding duration, and increases in clutch and brood size to compensate for lower survival. Other species-specific changes include changes in hormonal state, body state, and genetic differences from rural populations. We identify gaps in research, with a paucity of studies in tropical cities and a need for greater examination of traits that influence persistence and success in native vs. introduced populations.

The urban contrast: A nationwide assessment of avian diversity in Mexican cities

In this study we focused on urban bird diversity across Mexico, a megadiverse country, with a special focus on the relative role of urban greenspaces and heavily-built sites. We considered a country-wide approach, including 24 different sized Mexican cities. Our aims were to describe the urban bird diversity in focal cities and further assess the relationships between it and the biogeographic region where cities are located, their size, elevation, and annual rainfall. Additionally, we evaluated differences in the functional composition of bird communities in both studied urban scenarios (i.e., urban greenspaces, heavily-built sites). Our results confirm that urban greenspaces are home to a large proportion of species when contrasted with heavily-built sites. While total species richness and species richness of greenspaces were related with the cities' biogeographic region -with higher species richness in the Neotropical region and Transition Zone-, the relationship did not hold true in heavily-built sites. We found that annual rainfall was negatively related to bird richness in heavily-built sites, suggesting that species from arid systems can be more tolerant to urbanization. Regarding the bird functional group assessment, results show a clear differentiation between the functional groups of greenspaces and those of heavily-built sites, with granivores and omnivores associated with the latter and a highly diverse array of functional groups associated with urban greenspaces.

Soil Mesofauna Community Changes in Response to the Environmental Gradients of Urbanization in Guangzhou City

There has been a recent increase in interest on how urbanization affects soil fauna communities. However, previous studies primarily focused on some limited land use types or line transects of urban-rural gradients. At family and higher taxonomic levels, we investigated the changes of soil mesofauna communities (abundance, species richness, and community structure) with urbanization intensity along different disturbance features in 47 sites evenly located in downtown Guangzhou and adjacent regions. The 47 research sites were classified into four ecosystem types mainly according to the location (rural/urban), vegetation cover, and management intensity. In turn, the four types with increasing urbanization intensity were rural forest, urban forest, urban woodland, and urban park. Firstly, the role of urban soil property (soil physicochemical characteristic and soil heavy metal content) in regulating soil mesofauna community was investigated. The results showed that soil mesofauna abundance and diversity decreased with increasing soil pH, total nitrogen content (TN), and heavy metal comprehensive index (CPI). Soil Pb decreased soil mesofauna species richness (taxa number) and regulated soil mesofauna community structure. Secondly, we examined the effects of landscape changes on the soil mesofauna community. We found impervious surface (IS) ratio did not predict changes in soil mesofauna abundance, species richness, or community structure. Instead, IS ratio was positively correlated with soil pH, soil TN, and CPI. After excluding sites that belonged to rural forests and urban parks, site area was positively correlated with soil mesofauna abundance. Thirdly, our results revealed significant differences in soil property, landscape trait, and soil mesofauna community among the four ecosystem types. Interestingly, urban forest, the one lightly disturbed by urbanization, but not rural forest, had the highest soil mesofauna abundance. Soil mesofauna abundance in urban woodlands was similar to that in urban parks, which was about half of that in urban forests. Species richness in urban parks was 21% lower than that in rural forests. Our results also showed that urban woodland and urban parks had distinct mesofauna community structures compared to those in rural forests and urban forests. In conclusion, the present study suggested that (1) soil property changes due to urbanization, such as increased pH and heavy metal enrichment in urban soil, decreased soil mesofauna abundance and species richness, changed community structure, and mediated the effect of landscape change on soil mesofauna community; (2) however, soil and landscape changes could not explain the increase of abundance in urban forests, which supported the intermediate disturbance hypothesis.

Physiological stress does not increase with urbanization in European blackbirds: Evidence from hormonal, immunological and cellular indicators

Urbanization changes the landscape structure and ecological processes of natural habitats. While urban areas expose animal communities to novel challenges, they may also provide more stable environments in which environmental fluctuations are buffered. Species´ ecology and physiology may determine their capacity to cope with the city life. However, the physiological mechanisms underlying organismal responses to urbanization, and whether different physiological systems are equally affected by urban environments remain poorly understood. This severely limits our capacity to predict the impact of anthropogenic habitats on wild populations. In this study, we measured indicators of physiological stress at the endocrine, immune and cellular level (feather corticosterone levels, heterophil to lymphocyte ratio, and heat-shock proteins) in urban and non-urban European blackbirds (Turdus merula) across 10 European populations. Among the three variables, we found consistent differences in feather corticosterone, which was higher in non-urban habitats. This effect seems to be dependent on sex, being greater in males. In contrast, we found no significant differences between urban and non-urban habitats in the two other physiological indicators. The discrepancy between these different measurements of physiological stress highlights the importance of including multiple physiological variables to understand the impact of urbanization on species' physiology. Overall, our findings suggest that adult European blackbirds living in urban and non-urban habitats do not differ in terms of physiological stress at an organismal level. Furthermore, we found large differences among populations on the strength and direction of the urbanization effect, which illustrates the relevance of spatial replication when investigating urban-induced physiological responses.

The worldwide impact of urbanisation on avian functional diversity

Urbanisation is driving rapid declines in species richness and abundance worldwide, but the general implications for ecosystem function and services remain poorly understood. Here, we integrate global data on bird communities with comprehensive information on traits associated with ecological processes to show that assemblages in highly urbanised environments have substantially different functional composition and 20% less functional diversity on average than surrounding natural habitats. These changes occur without significant decreases in functional dissimilarity between species; instead, they are caused by a decrease in species richness and abundance evenness, leading to declines in functional redundancy. The reconfiguration and decline of native functional diversity in cities are not compensated by the presence of exotic species but are less severe under moderate levels of urbanisation. Thus, urbanisation has substantial negative impacts on functional diversity, potentially resulting in impaired provision of ecosystem services, but these impacts can be reduced by less intensive urbanisation practices.

Land-sharing vs. land-sparing urban development modulate predator-prey interactions in Europe

Urban areas are expanding globally as a consequence of human population increases, with overall negative effects on biodiversity. To prevent the further loss of biodiversity, it is urgent to understand the mechanisms behind this loss to develop evidence-based sustainable solutions to preserve biodiversity in urban landscapes. The two extreme urban development types along a continuum, land-sparing (large, continuous green areas and high-density housing) and land-sharing (small, fragmented green areas and low-density housing) have been the recent focus of debates regarding the pattern of urban development. However, in this context, there is no information on the mechanisms behind the observed biodiversity changes. One of the main mechanisms proposed to explain urban biodiversity loss is the alteration of predator-prey interactions. Using ground-nesting birds as a model system and data from nine European cities, we experimentally tested the effects of these two extreme urban development types on artificial ground nest survival and whether nest survival correlates with the local abundance of ground-nesting birds and their nest predators. Nest survival (n = 554) was lower in land-sharing than in land-sparing urban areas. Nest survival decreased with increasing numbers of local predators (cats and corvids) and with nest visibility. Correspondingly, relative abundance of ground-nesting birds was greater in land-sparing than in land-sharing urban areas, though overall bird species richness was unaffected by the pattern of urban development. We provide the first evidence that predator-prey interactions differ between the two extreme urban development types. Changing interactions may explain the higher proportion of ground-nesting birds in land-sparing areas, and suggest a limitation of the land-sharing model. Nest predator control and the provision of more green-covered urban habitats may also improve conservation of sensitive birds in cities. Our findings provide information on how to further expand our cities without severe loss of urban-sensitive species and give support for land-sparing over land-sharing urban development.

Biodiversity within the city: Effects of land sharing and land sparing urban development on avian diversity

Urbanization, one of the most extreme human-induced environmental changes, is negatively affecting biodiversity worldwide, strongly suggesting that we should reconcile urban development with conservation. Urbanization can follow two extreme types of development within a continuum: land sharing (buildings mixed with dispersed green space) or land sparing (buildings interspersed with green patches that concentrate biodiversity-supporting vegetation). Recent local-scale studies indicate that biodiversity is typically favored by land sparing. We investigated which of these two types of urbanization is associated with a higher taxonomic (i.e. species richness), functional, and phylogenetic diversity of birds. To do so, we collected information on breeding and wintering bird assemblages in 45 land-sharing and 45 land-sparing areas in nine European cities, which provide the first attempt to explore this question using a large geographical scale and temporal replication. We found that land-sharing urban areas were significantly associated with a higher taxonomic and functional diversity of birds during winter, but not during the breeding season (with only a marginally significant effect for functional diversity). We found no association between the type of urban development and phylogenetic diversity. Our findings indicate that not all components of avian diversity are similarly affected by these two means of urban planning and highlight the importance of integrating the temporal perspective into this kind of studies. Our results also offer useful information to the current debate about the trade-off between biodiversity conservation and human well-being in the context of land sharing and sparing urban practices. In addition, we found that certain small-scale urban landscape characteristics (i.e. few impervious surfaces, high water or tree cover) and human practices (i.e. bird feeders or plants with berries) can help maintaining more diverse urban bird assemblages. We provide specific suggestions for both policymakers and citizens that hopefully will help to create more biodiversity-friendly cities in the future.

Urbanization and Human Population Favor Species Richness of Alien Birds

Human activities like urbanization and agriculture affect spatial biodiversity patterns. The presence and activities of humans richly benefit alien species, but native species usually decline in human-impacted areas. Considering that the richness of alien and native species are inter-related, we explored the effect of human population density, human-related land uses (agricultural and urban), and natural land area on avian (alien and native) species richness of Massachusetts for two time periods using Generalized Additive Models. Avian alien species richness increased with native species richness in both time periods. Despite the predominant role of native species richness as a major driver of alien species richness, human activities play an important additional role in shaping species richness patterns of established aliens. Human-related land uses (urban and agricultural) and human population favored alien species richness in both time periods. Counter to expectations, human activities were also positively associated to native avian species richness. Possible explanations of these patterns may include habitat heterogeneity, increased availability of resources, and reduced predation risk.