Jukka Jokimäki

Loss of migration and urbanization in birds: a case study of the blackbird (Turdus merula).

Many organisms have invaded urban habitats, although the underlying factors initially promoting urbanization remain poorly understood. Partial migration may facilitate urbanization because such populations benefit from surplus food in urban environments during winter, and hence enjoy reduced fitness costs of migratory deaths. We tested this hypothesis in the European blackbird Turdus merula, which has been urbanized since the 19th century, by compiling information on timing of urbanization, migratory status, and population density for 99 cities across the continent. Timing of urbanization was spatially auto-correlated at scales up to 600xa0km. Analyses of timing of urbanization revealed that urbanization occurred earlier in partially migratory and resident populations than in migratory populations of blackbirds. Independently, this effect was most pronounced in the range of the distribution that currently has the highest population density, suggesting that urbanization facilitated population growth. These findings are consistent with the hypothesis that timing of urbanization is facilitated by partial migration, resulting in subsequent residency and population growth.

Urbanized birds have superior establishment success in novel environments

Many animals have adapted to the proximity of humans and thereby gained an advantage in a world increasingly affected by human activity. Numerous organisms have invaded novel areas and thereby increased their range. Here, we hypothesize that an ability to thrive in urban habitats is a key innovation that facilitates successful establishment and invasion. We test this hypothesis by relating the probability of establishment by birds on oceanic islands to the difference in breeding population density between urban and nearby rural habitats as a measure of urbanization in the ancestral range. This measure was the single-most important predictor of establishment success and the only statistically significant one, with additional effects of sexual dichromatism, number of releases and release effort, showing that the ability to cope with human proximity is a central component of successful establishment. Because most invasions occur as a consequence of human-assisted establishment, the ability to cope with human proximity will often be of central importance for successful establishment.

Effects of urbanization on breeding birds in European towns: Impacts of species traits

Urbanization acts as a filter on bird species behavioral traits so that only few species can tolerate urban constraints. We analyzed how behavioral traits (nesting, feeding, and migratory habits) of breeding bird species affect their frequency of occurrence in the urban centers of 38 European towns. We used binary logistic regression analysis to predict the bird species traits belonging to each trait group. A total of 108 species (21% of the European breeding bird species) were found to breed in the European town centers. According to our broad-scale analyses the bird species most frequently breeding in town centers nest in buildings and/or buildings have diverse diets, in trees (40%) and are resident omnivores, or relied on seeds or fruits as their sources of food. However, almost all bird species also fed on arthropods (92%) during the breeding season. Only a few urban bird species bred on the ground. Four out of the studied 108 species were non-native and five species were predators. Our broad-scale results from Europe indicate that bird species with different behavioral traits can respond differently to urbanization. Bird species that nest in cavities/buildings have diverse diets, that benefit a resident way-of-life, may have an advantage in living and settling in European town centers. Our results from Europe may provide insights related to the development of bird assemblages in the urban core areas of the New World.

Residential areas support overwintering possibilities of most bird species

Spatial variation in wintering bird communities in different types of urban residential areas is poorly understood. The objective of tills study was to find out which bird species from the regional species pool are able to inhabit residential areas, whether bird communities in different types of residential area differ from one another, and what are the factors affecting birds. We conducted our study in five apartment-building areas, five family-house areas, and five villages in northern Finland by using the single-visit study plot method during five winters, i.e. 1998/1999–2003/2004. Oldgrowth-forest-specialist species, in particular, avoided residential areas, whereas the other species appeared to benefit from residential development. The species richness, the total number of individuals, and the abundance of most of the species were higher in the family-house areas and in villages than in apartment-building areas. The proportion of individuals belonging to resident species was higher in the apartment-building areas than in the other habitats, whereas the proportion of individuals belonging to feeding-table species was higher in the villages than in the other habitats. The species richness and the total number of individuals increased with the increasing number of feeding tables and decreased with increasingly larger proportions of apartment buildings within the study plot. Parus montanus, P. major, P. caeruleus, Passer domesticus, and Carduelis flammea benefitted from feeding tables. Our study demonstrated that carefully planned winter feeding programmes can enhance the wintering possibilities for birds, and thus promote the biodiversity in urban ecosystems at northern latitudes.

Rural-Urban Differences in Escape Behavior of European Birds across a Latitudinal Gradient

Behavioral adjustment is a key factor that facilitates species’ coexistence with humans in a rapidly urbanizing world. Because urban animals often experience reduced predation risk compared to their rural counterparts, and because escape behaviour is energetically costly, we expect that urban environments will select for increased tolerance to humans. Many studies have supported this expectation by demonstrating that urban birds have reduced flight initiation distance (FID = predator-prey distance when escape by the prey begins) than rural birds. Here we advanced this approach and, for the first time, assessed how 32 species of birds, found in 92 paired urban-rural populations, along a 3,900 km latitudinal gradient across Europe, changed their predation risk assessment and escape strategy as a function of living in urban areas. We found that urban birds took longer than rural birds to be alerted to human approaches, and urban birds tolerated closer human approach than rural birds. While both rural and urban populations take longer to be aware of an approaching human as latitude increased, this behavioral change with latitude is more intense in urban birds (for a given unit of latitude, urban birds increased their distance more than rural birds). We also found that as mean alert distance was shorter, urban birds escaped more quickly from approaching humans, but there was no such a relationship in rural populations. Although both rural and urban populations tended to escape more quickly as latitude increased, urban birds delayed their escape more at low latitudes when compared with rural birds. These results suggest that urban birds in Europe live under lower predation risk than their rural counterparts. Furthermore, the patterns found in our study indicate that birds prioritize the reduction of on-going monitoring costs when predation risk is low. We conclude that splitting escape variables into constituent components may provide additional and complementary information on the underlying causes of escape. This new approach is essential for understanding, predicting, and managing wildlife in a rapidly urbanizing world.

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

Abstract 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.

Variation and long-term trends in the timing of breeding of different Eurasian populations of Common Redstart Phoenicurus phoenicurus

Abstract Changes in the timing of reproduction of birds should provide good evidence of large-scale climate fluctuations. However, geographically separate populations of one species may respond variably. We analyzed egg laying dates of nine Eurasian populations of the Common Redstart Phoenicurus phoenicurus collected between 1969 and 2010. The timing of breeding differed greatly with latitude: the populations in the north started later, a breeding pair produced only one brood per season and the breeding season was shorter. Both yearly minimum and median first-egg laying dates advanced with increases in local air temperature, but the more northern populations had started at much lower temperatures, which was probably caused by the stimulation of photoperiod. The effects of large-scale climatic patterns (North Atlantic Oscillation, East Atlantic, Scandinavia/Eurasia-1) on the first-egg laying date were low. The egg laying dates advanced over the observed decades in all populations, although at a variable rate. Seven selected populations with the most complete data for the period 1986–2010 revealed an advancement of median first-egg laying dates of 0.11xa0days/year and 1.31xa0days/°C. The effect on minimum first-egg laying dates was smaller. The changes observed in two populations in Ural and western Siberia were smaller than those found in more westerly populations (Finland, central Europe). The timing of the start of breeding is probably less affected by climate change than the timing of spring migration, documented by European ornithological stations.ZusammenfassungVariation und langfristige Trends im zeitlichen Ablauf der Brut von verschiedenen eurasischen Populationen des Gartenrotschwanzes Phoenicurus phoenicurusn Änderungen der Fortpflanzungszeiträume von Vögeln sollten gute Hinweise auf großräumige Klimaschwankungen geben. Allerdings können geographisch getrennte Populationen einer Art unterschiedlich reagieren. Wir werteten die Eiablagedaten von neun eurasischen Populationen des Gartenrotschwanzes aus dem Zeitraum 1969–2010 aus. Der Brutzeitraum unterschied sich mit dem Breitengrad erheblich: Populationen im Norden beginnen später, ein Brutpaar hat nur eine Brut pro Saison und die Brutsaison ist kürzer. Sowohl die jährlich Frühsten wie auch die mittleren Ersteiablagedaten verfrühten sich mit Erhöhung der lokalen Lufttemperatur, wobei die nördlicheren Populationen schon bei deutlich niedrigeren Temperaturen anfingen, was vermutlich mit einer Stimulation durch die Tageslänge zu erklären ist. Die Auswirkungen von großräumigen Klimamustern (North Atlantic Oscillation, East Atlantic, Scandinavia/Eurasia-1) auf die Ersteiablagetermine waren gering. Der Zeitpunkt der Eiablage verfrühte sich bei allen beobachteten Populationen im Verlauf des Beobachtungszeitraums, allerdings mit unterschiedlicher Geschwindigkeit. Bei sieben ausgewählten Populationen mit den umfangreichsten Datensätzen für den Zeitraum von 1986 bis 2010xa0lässt sich eine Verfrühung des mittleren Zeitpunkts der ersten Eiablage um 0.11xa0Tage/Jahr und 1.31xa0Tage/°C erkennen. Die Auswirkung auf den frühesten Zeitpunkt der ersten Eiablage war geringer. Die Veränderungen, die in zwei Populationen im Ural und in Westsibirien beobachtet werden konnten, waren geringer als bei weiter westlich gelegenen Populationen (Finnland, Mitteleuropa). Der Brutbeginn ist möglicherweise weniger vom Klimawandel als vom Zeitpunkt des Frühjahrszugs abhängig, wie er von europäischen Beobachtungs- und Beringungsstationen dokumentiert wird.

Scale dependence of biotic homogenisation by urbanisation: a comparison of urban bird communities between central Argentina and northern Finland: European Journal of Ecology

Abstract Recent studies showed contrasting results about the homogenising force of urbanisation on bird community composition at large and regional scales. We studied whether urbanisation promotes the homogenisation of wintering bird communities and if this varies when comparing towns located within a specific region and towns located in two different biomes of two countries. We used both similarity indices based on the presence/absence data and the abundance data in comparing communities. Processes governing bird community dissimilarity between urbanisation levels were examined with the partitioning of Sörensen index in species turnover and nestedness. We made bird surveys in town centres and suburban habitats of three cities located in the Pampean region of Argentina and in the boreal region of Finland using a single-visit study plot method. Rarefacted species richness did not differ amongst the town centres between the countries, but it was higher in the suburban areas of Argentina than in Finland. At the country-level comparison, we found a higher similarity amongst the town centres than amongst the suburban areas; whereas at the regional comparison, similarity between town centres was comparable to the similarity between suburban areas. The use of an abundance-based index produced a higher similarity between town centre communities of both countries than when using a presence-based index. The dissimilarity between habitats in Argentina was related to nestedness and to species turnover in Finland. Our results indicate that urban-based biotic homogenisation of bird communities is dependent on the scale used, being more evident when comparing cities of different biomes where the same and abundant bird species, such as sparrows and doves, dominate. At the regional scale, quite a high beta-diversity can still be found within urban habitats. Processes of community dissimilarity between urban habitats may differ according to the regional pool of species, being more related to nestedness toward the tropics.

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

Life-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.