Urbanization and species occupancy frequency distribution patterns in core zone areas of European towns

More and more of the globe is becoming urbanized. Thus, characterizing the distribution and abundance of species occupying different towns is critically important. The primary aim of this study was to examine the effect of urbanization and latitude on the patterns of species occupancy frequency distribution (SOFD) in urban core zones of European towns (38 towns) along a 3850-km latitudinal gradient. We determined which of the three most common distributional models (unimodal-satellite dominant, bimodal symmetrical, and bimodal asymmetrical) provides the best fit for urban bird communities using the AICc-model selection procedure. Our pooled data exhibited a unimodal-satellite SOFD pattern. This result is inconsistent with the results from previous studies that have been conducted in more natural habitats, where data have mostly exhibited a bimodal SOFD pattern. Large-sized towns exhibited a bimodal symmetric pattern, whereas smaller-sized towns followed a unimodal-satellite dominated SOFD pattern. The difference in environmental diversity is the most plausible explanation for this observation because habitat diversity of the study plots decreased as urbanization increased. Southern towns exhibited unimodal satellite SOFD patterns, central European towns exhibited bimodal symmetric, and northern towns exhibited bimodal asymmetric SOFD patterns. One explanation for this observation is that urbanization is a more recent phenomenon in the north than in the south. Therefore, more satellite species are found in northern towns than in southern towns. We found that core species in European towns are widely distributed, and their regional population sizes are large. Our results indicated that earlier urbanized species are more common in towns than the species that have urbanized later. We concluded that both the traits of bird species and characteristics of towns modified the SOFD patterns of urban-breeding birds. In the future, it would be interesting to study how the urban history impacts SOFD patterns and if the SOFD patterns of wintering and breeding assemblages are the same

Long-Term Winter Population Trends of Corvids in Relation to Urbanization and Climate at Northern Latitudes

SIMPLE SUMMARY: Corvids (e.g., crows, magpies and jays) are an important part of urban settlements, especially during winter. To understand the factors affecting the long-term population trends of corvids, we counted wintering corvids in 31 human settlements along a 920 km latitudinal gradient in Finland during four winters between 1991 and 2020. We detected a total of five corvid species, from which the Hooded Crow, the Eurasian Magpie and the Eurasian Jackdaw were found to be common. During the study period, the number of Eurasian Jackdaws increased, and their distribution range moved northwards. No corresponding changes were observed for the Hooded Crow or the Eurasian Magpie. Neither the local-level urban-, climate- nor food-related factors correlated with the changes in the numbers and growth rates of the corvids. No interspecific interactions were observed. We assume that the Eurasian Jackdaw has benefitted from the decreased persecution, and probably also from the large-scale climate warming. Our results suggest that urban settlements are quite stable wintering environments for generalist and omnivorous corvids. ABSTRACT: Corvids (crows, magpies, jays) live in a close association with humans, and therefore knowledge about their population status and changes will be an essential part of monitoring the quality of urban environments. Wintering bird populations can track habitat and climate changes more rapidly than breeding populations. We conducted a long-term (1991–2020) winter census of corvid species in 31 human settlements along a 920 km latitudinal gradient in Finland. We observed a total of five corvid species: the Eurasian Magpie (occurring in 114 surveys out of 122; total abundance 990 ind.), the Hooded Crow (in 96 surveys; 666 ind.), the Eurasian Jackdaw (in 51 surveys; 808 ind.), the Eurasian Jay (in 5 surveys; 6 ind.) and the Rook (in 1 survey; 1 ind.). Only the numbers of the Eurasian Jackdaw differed between the study winters, being greater at the end of the study period (2019/2020) than during the earlier winters (1991/1992 and 1999/2000). The average growth rate (λ) of the Eurasian Jackdaw increased during the study period, whereas no changes were observed in the cases of the Hooded Crow or the Eurasian Magpie. The growth rate of the Eurasian Jackdaw was greater than that observed in the Finnish bird-monitoring work, probably because our data came only from the core area of each human settlement. Even though the number of buildings and their cover increased in the study plots, and the winter temperature differed between winters, the average growth rate (λ) of corvid species did not significantly correlate with these variables. These results suggest that urban settlements are stable wintering environments for the generalist corvids. The between-species interactions were all positive, but non-significant. Despite the total number of winter-feeding sites being greater during the winter of 1991/1992 than during the winter of 2019/2020, the changes in the numbers of feeding stations did not correlate with the growth rates of any corvid species. We assume that the Eurasian Jackdaw has benefitted from the decreased persecution, and probably also from large-scale climate warming that our study design was unable to take in to account. Our results indicated that wintering corvid populations succeed well in the human settlements in Finland. We recommend conducting long-term corvid research, also during breeding season, to understand more detailed causes of the population changes of corvids along an urban gradient. Without year-round long-term monitoring data, the conservation and management recommendations related to the corvid species in urban habitats may be misleading

Differential Long-Term Population Responses of Two Closely Related Human-Associated Sparrow Species with Respect to Urbanization

Urban planning and management need long-term population level studies for evaluating how urbanization influences biodiversity. Firstly, we reviewed the current population trends of the House Sparrow (Passer domesticus) and the Eurasian Tree Sparrow (Passer montanus) in Europe, and evaluated the usefulness of citizens’ science projects to monitor these species in Finland. Secondly, we conducted a long-term (1991–2020) winter field study in 31 urban settlements along a 950 km north–south extent in Finland to study how latitude, weather and urbanization influence on sparrow’s growth rates. The House Sparrow is declining in 15 countries, and increasing in 5, whereas the Eurasian Tree Sparrow is declining in 12 and increasing in 9 European countries. The trend of the House Sparrow was significantly negative in continental Europe. However, the trend of the Eurasian Tree Sparrow was not significant. Both species have declined simultaneously in six countries, whereas in four countries, their trends are opposite. Citizen-based, long-term (2006–2020) winter season project data indicated that House Sparrow has decreased, whereas Eurasian Tree Sparrow has increased in Finland. However, the short-term (2013–2020) breeding season citizen-based project data did not indicate significant changes in the occupation rate of sparrows. Our long-term (1991–2020) field study indicated that wintering populations of the House Sparrow have decreased, whereas the Eurasian Tree Sparrows have both expanded their wintering range and increased their population size. Based on our winter count data, latitude and weather did not significantly influence the growth rates of sparrows. When the human population increased within the study plot, House Sparrow populations decreased, and vice versa. There was also a trend that a decreasing number of feeding sites has decreased the House Sparrow numbers. Urban-related factors did not influence the growth rate of the Eurasian Tree Sparrow. Our results indicate that the colonization of a new, even closely related species does not influence negatively on earlier urbanized species. It is probable that the niches of these sparrow species are different enough for allowing them to co-occur. The House Sparrow mainly nests on buildings, whereas the Eurasian Tree Sparrow can easily accept, e.g., nest boxes. Urban planning should take care of both the food availability and nest sites availability for both sparrow species

Adjusting risk-taking to the annual cycle of long-distance migratory birds

International audienceLife-history theory predicts that current behaviour affects future reproduction, implying that animals should optimise their escape strategies to reflect fitness costs and benefits of premature escape. Both costs and benefits of escape may change temporally with important consequences for the evolution of escape strategies. Moreover, escape strategies of species may differ according to their positions on slow-fast pace of life gradients. We studied risk-taking in long-distance migratory animals, waders (Charadriiformes), during the annual cycle, i.e., breeding in Europe, stopover in the Middle East and wintering in tropical Africa. Phylogenetically informed comparative analyses revealed that risk-taking (measured as flight initiation distance, FID) changed significantly over the year, being lowest during breeding and peaking at stopover sites. Similarly, relationships between risk-taking and life-history traits changed among stages of the annual cycle. While risk-taking significantly decreased with increasing body mass during breeding, risk-taking-body mass relationship became marginally significant in winter and disappeared during migration. The positive trend of risk-taking along slow-fast pace of life gradient measured as adult survival was only found during breeding. The season-dependent relationships between risk-taking and life history traits suggest that migrating animals respond to fluctuating environments by adopting behavioural plasticity

Flight initiation distance and refuge in urban birds

Risk-taking in birds is often measured as the flight initiation distance (FID), the distance at which individuals take flight when approached by a potential predator (typically a human). The ecological factors that affect avian FID have received great attention over the past decades and meta-analyses and comparative analyses have shown that FID is correlated with body mass, flock size, starting distance of the approaching human, density of potential predators, as well as varying along rural to urban gradients. However, surprisingly, only few studies (mainly on reptiles and mammals) have explored effects of different types of refugia and their availability on animal escape decisions. We used Bayesian regression models (controlling for the phylogenetic relatedness of bird species) to explore changes in escape behaviour recorded in European cities in relationship to the birds' distance to the nearest refuge and distance fled to the refuge. In our analyses, we also included information on the type of refuge, built-up and vegetation cover, starting distance, flock size, urbanization level, and type of urban habitat. We found that birds preferred tree refuges over artificial and bush refuges. Birds escaped earlier if the distance to the nearest refuge of any type was longer and if birds fled longer distances to the refuge. FID was shorter when birds used bushes as refugia or landed on the ground after flushing compared to using artificial refugia. Similarly, the distance fled to a refuge was shortest when using bushes, and increased when escaping to artificial substrates and trees. Birds were more timid in suburban than core areas of cities, cemeteries than parks, and in areas with higher bush cover but lower cover of built-up areas and trees. Our findings provide novel information regarding the importance of refuge proximity and type as factors affecting the escape behaviour of urban birds.MD was funded by MCIN/AEI/10.13039/501100011033 to the project URBILAND (PID2019-107423GA-I00).Peer reviewe

The role of residential habitat type on the temporal variation of wintering bird assemblages in northern Finland

Wintertime ecological studies conducted in different kinds of residential areas over sev-eral winters have thus far been lacking. The objective of this study was to analyze if the between-winter variability of bird communities differs between urban residential habitat types. The study was conducted in five blocks of flats areas, five single-family house ar-eas, and five villages in Rovaniemi, northern Finland, during five winters. Birds were sur-veyed using a single-visit study plot (30 ha) method. The average between-winter varia-tion (CV%) in bird species richness was 27% and in bird abundance was 53%, and these values did not differ between the three types of residential areas. Temporal variation of species in residential areas was species-specific. The lowest between-winter variation was observed for omnivore or feeding table species such as the Great tit Parus major (50%), Magpie Pica pica (53%) and House Sparrow Passer domesticus (76%). The high-est variation was observed for berry-eating species, such as the Bullfinch Pyrrhula pyrrhula (196%) and Waxwing Bombycilla garrulus (192%). The between-winter vari-ation (CV%) of abundance of most species was greater in the blocks of flats areas than in the other residential-area types. The between-winter average qualitative similarity was 76.1% in the blocks of flats areas, 80.0% in the single-family house areas, and 78.0% in the villages, and these values did not differ between types of residential areas or between study winters. Stability of winter communities decreased from the centre to the periphery of Rovaniemi. We suggest that the stabilizing, warmer microclimate near the urban core of the town partly explains this result. The average species turnover rate (%) in the block of flats areas was 22.8, in single-family house areas was 20.5, and in the villages was 21.6. In general, the lowest between-winter similarities, highest species turnover rates, and the highest between-winter variation of abundance of individual species were observed in ar-eas of blocks of flats. Our results suggest that single-family house and village areas are better overwintering areas for wintering birds than areas of blocks-of-flats. Intensive win-ter feeding might stabilize the between-winter variation of bird assemblages especially in single-family house areas. In addition, the warmer microclimate near the urban core might probably also stabilizes variation in residential bird assemblages