Accelerated farmland bird population declines in European countries after their recent EU accession.

Agricultural intensification is a major driver of global biodiversity loss. In Europe, intensification progressed over the 20th century and was accelerated by instruments of the EU's Common Agricultural Policy. Central and Eastern European (CEE) countries standing outside the EU until the beginning of the 21st century employed less intensive farming and are considered one of the continent's farmland biodiversity strongholds. Their recent EU accession might be either viewed as a threat to farmland biodiversity due to the availability of funds to increase agricultural production or as an opportunity to implement conservation measures aimed to preserve biodiversity. Here we assessed these possibilities using long-term monitoring data on farmland bird populations in seven CEE countries. We tested whether mean relative abundance and population trends changed after countries' EU accession, and whether such changes also occurred in agricultural management and conservation measures. Both agricultural intensity and spending for agri-environmental and climatic schemes increased when the CEE countries joined the EU. At the same time, farmland bird populations started to decline and their relative abundance was lower after than before EU accession. In addition, increases in fertilizer application were negatively associated with annual changes in relative farmland bird population sizes, indicating a negative impact of intensive agriculture. Taken together, these results indicate that despite the great power of the EU's environmental legislation to improve the population status of species at risk, this does not apply to farmland birds. In their case, the adverse impacts of agricultural intensification most likely overrode the possible benefits of conservation measures. To secure this region as one of the continent's farmland biodiversity strongholds, policy and management actions are urgently needed.

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.

Ecological barriers mediate spatiotemporal shifts of bird communities at a continental scale.

Species' range shifts and local extinctions caused by climate change lead to community composition changes. At large spatial scales, ecological barriers, such as biome boundaries, coastlines, and elevation, can influence a community's ability to shift in response to climate change. Yet, ecological barriers are rarely considered in climate change studies, potentially hindering predictions of biodiversity shifts. We used data from two consecutive European breeding bird atlases to calculate the geographic distance and direction between communities in the 1980s and their compositional best match in the 2010s and modeled their response to barriers. The ecological barriers affected both the distance and direction of bird community composition shifts, with coastlines and elevation having the strongest influence. Our results underscore the relevance of combining ecological barriers and community shift projections for identifying the forces hindering community adjustments under global change. Notably, due to (macro)ecological barriers, communities are not able to track their climatic niches, which may lead to drastic changes, and potential losses, in community compositions in the future.

Farmland practices are driving bird population decline across Europe.

Declines in European bird populations are reported for decades but the direct effect of major anthropogenic pressures on such declines remains unquantified. Causal relationships between pressures and bird population responses are difficult to identify as pressures interact at different spatial scales and responses vary among species. Here, we uncover direct relationships between population time-series of 170 common bird species, monitored at more than 20,000 sites in 28 European countries, over 37 y, and four widespread anthropogenic pressures: agricultural intensification, change in forest cover, urbanisation and temperature change over the last decades. We quantify the influence of each pressure on population time-series and its importance relative to other pressures, and we identify traits of most affected species. We find that agricultural intensification, in particular pesticides and fertiliser use, is the main pressure for most bird population declines, especially for invertebrate feeders. Responses to changes in forest cover, urbanisation and temperature are more species-specific. Specifically, forest cover is associated with a positive effect and growing urbanisation with a negative effect on population dynamics, while temperature change has an effect on the dynamics of a large number of bird populations, the magnitude and direction of which depend on species' thermal preferences. Our results not only confirm the pervasive and strong effects of anthropogenic pressures on common breeding birds, but quantify the relative strength of these effects stressing the urgent need for transformative changes in the way of inhabiting the world in European countries, if bird populations shall have a chance of recovering.

Blood parasites (Trypanosoma, Leucocytozoon, Haemoproteus) in the Eurasian sparrowhawk (Accipiter nisus): diversity, incidence and persistence of infection at the individual level.

BACKGROUND: A high prevalence of parasites may result from life-long persistence of infection or from high reinfection rates. We have studied blood parasites in a breeding population of the accipitrid raptor, Eurasian sparrowhawk (Accipiter nisus), to determine parasite diversity and turnover. METHODS: During this 7-year study, 210 adult Eurasian sparrowhawks breeding in the city of Prague were checked for parasites using several diagnostic methods. RESULTS: In both female and male raptors, parasites of the genus Leucocytozoon were the most prevalent (92% and 85%, respectively) followed in decreasing order of prevalence by those of genus Trypanosoma (74% and 68%, respectively) and genus Haemoproteus (46% and 16%, respectively). The prevalence of all parasites increased with age in both sexes, with the females at each respective age having the higher prevalence. There was a positive association between Haemoproteus and Leucocytozoon infections. Persistence at the individual level was higher than incidence for Trypanosoma and Haemoproteus. In the case of Leucocytozoon and Trypanosoma, most individuals probably become infected in their first year of life or even before dispersal from the nest. The detected parasites belonged to Trypanosoma avium sensu stricto, Leucocytozoon sp. (haplotypes ACNI1 and ACNI3) and Leucocytozoon mathisi (haplotype ACNI4) and two new lineages of the Haemoproteus elani complex (ACCNIS6 and ACCNIS7). Detailed analysis of parasite lineages in individuals that were repeatedly sampled revealed lineage turnover that would otherwise remain hidden. Phylogenetic analysis revealed that the detected Haemoproteus belongs to a phylogenetically distant group whose taxonomic position requires further analysis. CONCLUSIONS: All three genera of blood parasites persist in infected individuals, thus enabling sustainability of vector transmission cycles. Prevalence increases with age; however, there is a high turnover of Leucocytozoon lineages. No clear evidence of parasite-induced mortality was found, and most of the individuals were infected early in life, particularly in the case of Leucocytozoon.

Comparing population trend estimates of migratory birds from breeding censuses and capture data at a spring migration bottleneck.

Europe has a well-established network of breeding bird monitoring that is used to produce supranational indices of population trends for many species. However, a comparison of breeding bird censuses with other methods may be beneficial to confirm the validity of such indices. The aim of this study was to assess the value of standardized capture data of migratory birds at migration bottlenecks as an indicator of the effective breeding populations. One limitation to this method is that several populations are co-occurring at these bottlenecks and their catchment areas need to be clearly identified to allow extrapolation of population indices. Here, we used standardized trends in capture numbers of 30 species on the island of Ponza, a migration bottleneck in the central Mediterranean, and compared them to population trends estimated in the putative catchment breeding areas between 2005 and 2016. The catchment areas were identified through the analysis of ring recoveries during the breeding season of birds passing through Ponza. Our results show an agreement between the population trends observed on Ponza and those in the breeding areas in 15 out of 30 species. The correlations were strongest in species with a more robust definition of the catchment areas, that is, species with more than 10 recoveries, and for which the recoveries were most likely of breeding birds. The main reason for disagreement between the two indices in the remaining species might be related to different intensity of sampling in different areas. This issue can be solved by further developing monitoring projects in underrepresented countries, as well as by intensifying monitoring through ringing, both in the breeding grounds and at migration bottlenecks. These results show that spring migration monitoring at bottlenecks has the potential to provide a valuable complement and an independent control of breeding bird surveys, allowing raising early warnings of population declines and contributing to their conservation.

Consistent response of bird populations to climate change on two continents.

Global climate change is a major threat to biodiversity. Large-scale analyses have generally focused on the impacts of climate change on the geographic ranges of species and on phenology, the timing of ecological phenomena. We used long-term monitoring of the abundance of breeding birds across Europe and the United States to produce, for both regions, composite population indices for two groups of species: those for which climate suitability has been either improving or declining since 1980. The ratio of these composite indices, the climate impact indicator (CII), reflects the divergent fates of species favored or disadvantaged by climate change. The trend in CII is positive and similar in the two regions. On both continents, interspecific and spatial variation in population abundance trends are well predicted by climate suitability trends.

Continent-scale global change attribution in European birds - combining annual and decadal time scales.

Species attributes are commonly used to infer impacts of environmental change on multiyear species trends, e.g. decadal changes in population size. However, by themselves attributes are of limited value in global change attribution since they do not measure the changing environment. A broader foundation for attributing species responses to global change may be achieved by complementing an attributes-based approach by one estimating the relationship between repeated measures of organismal and environmental changes over short time scales. To assess the benefit of this multiscale perspective, we investigate the recent impact of multiple environmental changes on European farmland birds, here focusing on climate change and land use change. We analyze more than 800 time series from 18 countries spanning the past two decades. Analysis of long-term population growth rates documents simultaneous responses that can be attributed to both climate change and land-use change, including long-term increases in populations of hot-dwelling species and declines in long-distance migrants and farmland specialists. In contrast, analysis of annual growth rates yield novel insights into the potential mechanisms driving long-term climate induced change. In particular, we find that birds are affected by winter, spring, and summer conditions depending on the distinct breeding phenology that corresponds to their migratory strategy. Birds in general benefit from higher temperatures or higher primary productivity early on or in the peak of the breeding season with the largest effect sizes observed in cooler parts of species' climatic ranges. Our results document the potential of combining time scales and integrating both species attributes and environmental variables for global change attribution. We suggest such an approach will be of general use when high-resolution time series are available in large-scale biodiversity surveys.

Common European birds are declining rapidly while less abundant species' numbers are rising.

Biodiversity is undergoing unprecedented global decline. Efforts to slow this rate have focused foremost on rarer species, which are at most risk of extinction. Less interest has been paid to more common species, despite their greater importance in terms of ecosystem function and service provision. How rates of decline are partitioned between common and less abundant species remains unclear. Using a 30-year data set of 144 bird species, we examined Europe-wide trends in avian abundance and biomass. Overall, avian abundance and biomass are both declining with most of this decline being attributed to more common species, while less abundant species showed an overall increase in both abundance and biomass. If overall avian declines are mainly due to reductions in a small number of common species, conservation efforts targeted at rarer species must be better matched with efforts to increase overall bird numbers, if ecological impacts of birds are to be maintained.

Trypanosomes and haemosporidia in the buzzard (Buteo buteo) and sparrowhawk (Accipiter nisus): factors affecting the prevalence of parasites.

The prevalences of heteroxenous parasites are influenced by the interplay of three main actors: hosts, vectors, and the parasites themselves. We studied blood protists in the nesting populations of raptors in two different areas of the Czech Republic. Altogether, 788 nestlings and 258 adult Eurasian sparrowhawks (Accipiter nisus) and 321 nestlings and 86 adult common buzzards (Buteo buteo) were screened for parasites by the microscopic examination of blood smears and by cultivation. We examined the role of shared vectors and parasite phylogenetic relationships on the occurrence of parasites. In different years and hosts, trypanosome prevalence ranged between 1.9 and 87.2 %, that of Leucocytozoon between 1.9 and 100 %, and Haemoproteus between 0 and 72.7 %. Coinfections with Leucocytozoon and Trypanosoma, phylogenetically distant parasites but both transmitted by blackflies (Simuliidae), were more frequent than coinfections with Leucocytozoon and Haemoproteus, phylogenetically closely related parasites transmitted by different vectors (blackflies and biting midges (Ceratopogonidae), respectively). For example, 16.6 % buzzard nestlings were coinfected with Trypanosoma and Leucocytozoon, while only 4.8 % with Leucocytozoon and Haemoproteus and 0.3 % with Trypanosoma and Haemoproteus. Nestlings in the same nest tended to have the same infection status. Furthermore, prevalence increased with the age of nestlings and with Julian date, while brood size had only a weak negative/positive effect on prevalence at the individual/brood level. Prevalences in a particular avian host species also varied between study sites and years. All these factors should thus be considered while comparing prevalences from different studies, the impact of vectors being the most important. We conclude that phylogenetically unrelated parasites that share the same vectors tend to have similar distributions within the host populations of two different raptor species.

A niche-based framework to assess current monitoring of European forest birds and guide indicator species' selection.

Concern that European forest biodiversity is depleted and declining has provoked widespread efforts to improve management practices. To gauge the success of these actions, appropriate monitoring of forest ecosystems is paramount. Multi-species indicators are frequently used to assess the state of biodiversity and its response to implemented management, but generally applicable and objective methodologies for species' selection are lacking. Here we use a niche-based approach, underpinned by coarse quantification of species' resource use, to objectively select species for inclusion in a pan-European forest bird indicator. We identify both the minimum number of species required to deliver full resource coverage and the most sensitive species' combination, and explore the trade-off between two key characteristics, sensitivity and redundancy, associated with indicators comprising different numbers of species. We compare our indicator to an existing forest bird indicator selected on the basis of expert opinion and show it is more representative of the wider community. We also present alternative indicators for regional and forest type specific monitoring and show that species' choice can have a significant impact on the indicator and consequent projections about the state of the biodiversity it represents. Furthermore, by comparing indicator sets drawn from currently monitored species and the full forest bird community, we identify gaps in the coverage of the current monitoring scheme. We believe that adopting this niche-based framework for species' selection supports the objective development of multi-species indicators and that it has good potential to be extended to a range of habitats and taxa.

An indicator of the impact of climatic change on European bird populations.

Rapid climatic change poses a threat to global biodiversity. There is extensive evidence that recent climatic change has affected animal and plant populations, but no indicators exist that summarise impacts over many species and large areas. We use data on long-term population trends of European birds to develop such an indicator. We find a significant relationship between interspecific variation in population trend and the change in potential range extent between the late 20(th) and late 21(st) centuries, forecasted by climatic envelope models. Our indicator measures divergence in population trend between bird species predicted by climatic envelope models to be favourably affected by climatic change and those adversely affected. The indicator shows a rapid increase in the past twenty years, coinciding with a period of rapid warming.

Developing indicators for European birds.

The global pledge to deliver 'a significant reduction in the current rate of biodiversity loss by 2010' is echoed in a number of regional and national level targets. There is broad consensus, however, that in the absence of conservation action, biodiversity will continue to be lost at a rate unprecedented in the recent era. Remarkably, we lack a basic system to measure progress towards these targets and, in particular, we lack standard measures of biodiversity and procedures to construct and assess summary statistics. Here, we develop a simple classification of biodiversity indicators to assist their development and clarify purpose. We use European birds, as example taxa, to show how robust indicators can be constructed and how they can be interpreted. We have developed statistical methods to calculate supranational, multi-species indices using population data from national annual breeding bird surveys in Europe. Skilled volunteers using standardized field methods undertake data collection where methods and survey designs differ slightly across countries. Survey plots tend to be widely distributed at a national level, covering many bird species and habitats with reasonable representation. National species' indices are calculated using log-linear regression, which allows for plot turnover. Supranational species' indices are constructed by combining the national species' indices weighted by national population sizes of each species. Supranational, multi-species indicators are calculated by averaging the resulting indices. We show that common farmland birds in Europe have declined steeply over the last two decades, whereas woodland birds have not. Evidence elsewhere shows that the main driver of farmland bird declines is increased agricultural intensification. We argue that the farmland bird indicator is a useful surrogate for trends in other elements of biodiversity in this habitat.