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Biodiversity monitoring is important as it allows to prioritize research into the causes of declines and assessing the efficacy of conservation measures. Regional assessments are valuable, because conservation policies and management are often implemented on national and sub-national level. We analyzed data from the German Common Bird Monitoring for 1990–2018. We derived indices of population size using standard log-linear models, based on point counts and route territory mapping at up to 1200 plots annually. We summarized species trends by ecological trait groups. Among the 93 common breeding birds, farmland birds declined strongly, birds of settlements declined. Forest birds initially declined, but recovered after ca. 2010. Wetland birds increased strongly, albeit the number of species with data was low. Consistent declines were found in ground-nesting birds, granivorous and invertebrate (other than insect)-feeding birds. Trends of insectivorous birds were stable on average, but farmland insectivores declined strongly since the year 2000. Long-distance migrants showed more negative trends compared to short-distance migrants and resident species. Species with narrow habitat niche declined disproportionally. Trends over the entire period were more negative in common species in the dataset (with a German breeding population of > 50 K and

Resource pulses are wide-ranging, influential ecosystem processes with effects permeating throughout the food web, sometimes over several years. In temperate forests, resource pulses may be triggered by mast seeding of one or several tree species, providing a key food source to a multitude of species. However, direct and indirect consequences of mast seeding for various seed and non-seed consumers, and interactions among them, are often poorly understood. Based on a 16-year data set from Germany, we evaluated several hypotheses concerning the relationships between (1) mast seeding and seed consumers, (2) seed and non-seed consumers, and (3) seed or non-seed consumers and extrinsic factors other than mast seeding. Abundances of Eurasian Jays Garrulus glandarius correlated negatively, but abundances of voles positively, with mast seeding of oak in the previous fall, while the abundances of Great Tits Parus major did not appear to be linked to mast seeding. The abundance of non-seed consumers, such as Wood Warblers Phylloscopus sibilatrix, but not Chiffchaffs Phylloscopus collybita, appeared to be linked indirectly to mast seeding of oak via voles. Specifically, Wood Warbler abundance negatively correlated with abundances of voles. Extrinsic factors other than mast seeding appeared to be unimportant. This study shows how the set of factors affecting a species at a large spatial scale may vary from the set of factors acting at smaller spatial scales, as obtained from the literature. Lastly, we illustrate how several taxa at various trophic levels of a temperate forest ecosystem in Central Europe are linked via resource pulses. Assessing ecological processes revolving around seed-based resource pulses is pivotal to understanding how changing mast seeding dynamics may alter an ecosystem.

Data collected by forest inventories like the third National Forest Inventory (NFI-3, 2011–2012) in Germany was proposed to monitor forest biodiversity and evaluate existing forest management practices on a national scale. A data set was created from the NFI-3 data for analysis purposes which contained variables relevant to the habitat requirements of native forest bird species. Information on the distribution and abundance of 20 native forest bird species was taken from the Atlas of German Breeding Birds (2005–2009, 3003 grid cells). They form two important ecological groups: cavity-nesting and deciduous forest birds. For the first time, this data was combined with NFI-3 data and analysed using Random Forest models and partial dependence plots to determine which forest variables recorded by the NFI-3 were most closely related to forest bird species richness and diversity in temperate forests. It was shown that changes in forest bird species diversity and richness correlate with the NFI data but the different sampling methods of the NFI and bird species data also created methodological challenges which are discussed. The most important drivers of the richness and diversity of deciduous forest and cavity-nesting bird species are forest stand age and forest ownership. Deciduous forest and cavity-nesting birds show a preference for the way state, federal and municipal forests are managed over private forests. Private forests have significantly lower deadwood volumes and high proportions of coniferous trees, both of which are forest characteristics that lower the richness and diversity of bird species. Our findings show that efforts to protect forest birds should target managed forests older than 100 and 200 years and forests with total deadwood volumes >46.3 m3/ha. Protected areas also exhibited higher diversity and richness of forest birds which highlight their importance as suitable target areas for the protection of forest birds.

SummaryBirds that are long-distance migrants partition their annual cycle among a number of locations over a large spatial range. The conservation of these species is particularly complex because it requires attention to a number of different and distant habitats based on knowledge of migratory phenology, routes and staging areas. In the case of the globally threatened Aquatic WarblerAcrocephalus paludicola, a habitat specialist that breeds in Europe and spends the boreal winter in sub-Saharan Africa, non-breeding staging areas were widely unknown until recently. We applied light-level geolocators to adult male Aquatic Warblers at breeding sites in Belarus and Ukraine. Data from eight retrieved geolocators confirmed a south-west and then westward migration route through Europe via the northern Mediterranean with staging sites on the Iberian Peninsula and occasionally France and north-west Africa. In sub-Saharan Africa, final staging areas were in Mali, either in the Inner Niger Delta or at (presumably) small water bodies in the desert, with one bird most likely staying in the north of Ivory Coast south of the previously assumed range. The birds probably stayed in the final staging areas for most of the non-breeding season, but the logger on only one bird provided data throughout the entire migration cycle. Pre-nuptial migration of the latter was by a more easterly route than the southward migration. Our study suggests that conservation strategies for Aquatic Warbler north of the Sahara should include consideration of unknown staging sites in the northern Mediterranean as well as on the Iberian Peninsula and in north-west Africa. South of the Sahara, our study demonstrates the importance of the Sahel for the conservation of the Aquatic Warbler, including both the major floodplains of the Niger River and small Sahelian wetlands that are under pressure from human development.

Land management causes changes in forest structure and thus influences the composition and abundance of communities of forest-inhabiting bird species. However, it is unclear how these changes translate into local habitat suitability for certain bird species given that detailed knowledge on habitat use by forest bird species is still scarce. We have analyzed the habitat preferences of 37 breeding bird species in 19 lowland beech forests, each with an average size of 40 ha. We used Jacobs habitat selection index to quantify preference or avoidance of certain forest developmental phases (fdp). Fdp divide the forest life cycle into different periods, each characterized by a certain combination of habitat parameters (canopy cover, tree dimension, deadwood amount, regeneration cover), thereby integrating several age-specific structural properties. We found that fdp representing the last third of the forest life cycle were significantly preferred by most of the bird species. Of the 37 bird species analyzed, 19 showed the highest preference for the terminal phase or the disintegration phase; this was especially true for hole breeders, semi-hole breeders, ground breeders and beech forest indicator species. Moreover, each bird species showed a characteristic profile of preferred and avoided fdp. Some bird species, such as several free breeders, also preferred younger fdp, such as gaps or regeneration phases. Further, mean fdp patch size turned out to be a strong predictor of bird community composition. Our study confirms that most bird species show a strong preference for later fdp, such as the terminal phase and disintegration phase. However, the simultaneous availability of a mixture of different fdp on local scales meets the habitat preferences of most species and promotes biodiversity of breeding bird communities in lowland beech forests.

We report the discovery of the first breeding population of Baillon's Crake Porzana pusilla in Senegambia, West Africa. From winter 2007–2010, 278 Baillon's Crakes were caught within and immediately north of Parc National des Oiseaux du Djoudj in the Senegal delta, as well as in a wetland in The Gambia at Pakali Ba. The records included 169 juvenile Baillon's Crakes, 23 of which were not fully fledged and were undoubtedly hatched in the area. The distribution of five assigned age intervals revealed that two consecutive broods were probably hatched within the breeding period, which is estimated to extend from September until February. During that period, the shallow Scirpus- and Sporobolus-marshes are still flooded and offer optimal habitat. The high number of captures suggests that a large population occurs in the Senegal delta. Furthermore, the species may be more abundant in Sahelian wetlands than was previously assumed. Sub-Saharan populations of P. pusilla are usually considered resident. However, due...

One approach to assess human impact on species’ population dynamics is to correlate ecological traits of species with their long-term population trends. Yet, few studies investigated population trends in multiple regions that differ in human impact to reveal which traits explain population trends over larger geographic areas and which only regionally. We examined the relationship between various species traits and long-term population trends of 57 common passerine bird species from 1991 to 2007 in three adjacent regions in central Europe that experienced differences in socioeconomic history: North-Western Germany, Eastern Germany and the Czech Republic. We tested effects of habitat, dietary and climatic niche, migratory strategy and cognitive ability, measured as relative brain size. We predicted that traits reflecting socioeconomic and land-use change had stronger effects in former communist countries than in North-Western Germany due to marked changes in these countries after 1990. We found that climatic niche and migratory strategy affected bird abundances similarly in all regions suggesting their influence is invariant across central Europe. In contrast, brain size showed regionally varying effects. The effects were negligible in North-Western Germany, slightly positive in Eastern Germany and strongly positive in the Czech Republic. Increases of species with large brains suggest that species with good cognitive abilities might have been better able to adapt to rapid socioeconomic change and make use of novel opportunities after the end of communism. Regional differences in population trends among species thus appear to be driven by an interaction between cognitive abilities and socioeconomic change.

We report the isolation and characterization of eleven microsatellite markers from the Aquatic Warbler (Acrocephalus paludicola) the only globally threatened passerine species in Europe. We tested the markers in 23 samples of the species collected in the Biebrza marshes, Poland, between 1990 and 1997. All markers were polymorphic, with 2–16 alleles per locus, and no differences were found between the observed and expected heterozygosity when applying Bonferroni correction and a table-wide significance level of 0.05. We found no evidence for linkage disequilibrium between the markers. The frequency of null alleles was 0.00–0.43. The new markers will allow further insight in the population genetics and population structure of the Aquatic Warbler. Assessing the potential connectivity between breeding populations and wintering areas can guide further conservation efforts.

The Aquatic Warbler is a threatened Afro-Palaearctic migrant with a largely unknown distribution in the winter (non-breeding) season. Protection of wintering sites may be crucial for the conservation of the species. Previous studies have identified extensive areas of north-western sub-Saharan Africa that could potentially be occupied by the species during winter. However, these studies have not necessarily differentiated between potentially suitable and unsuitable habitat types at a spatial resolution appropriate for targeting field surveys. To identify specific sites that could be occupied by non-breeding Aquatic Warblers at a scale appropriate for targeted field surveys, we adopted a modelling approach that combined recent sightings from Djoudj, Senegal, with land cover and climate data. We produced maps of potential distribution using three maximum entropy models. While a paucity of sightings prevented a full test of these maps on independent records, the areas that were predicted to be potentially occ...

Stable isotope analysis of feathers can be useful in the study of seasonal interactions and migratory connectivity in birds. For the PalaearcticAfrican migration system, however, the lack of isotope data from feathers of known origin in Africa renders the geographic assignment of birds captured on European breeding grounds to potential wintering areas problematic. Rectrices of the threatened aquatic warbler Acrocephalus paludicola grown in Africa were sampled across six European countries to assess whether birds in different breeding populations shared similar isotopic signatures and so were likely to have wintered in the same region in Africa. Freshly grown feathers of aquatic warblers collected at the only known wintering site in Senegal showed high variation in carbon, nitrogen, and hydrogen isotope ratios. Due to similarly high variation in isotope ratios of African-grown feathers within all breeding populations, it was not possible to determine whether different populations wintered in different regions. However, isotope signatures of 20% of birds captured on European breeding grounds fell outside the range of those captured in Senegal, suggesting a wider wintering distribution than is currently known. We therefore assessed whether the origin of these feathers could be estimated by trying to establish isotopic gradients across sub-Saharan West Africa. Feathers of three ecologically similar surrogate species were sampled from wetlands across a 3000 km east-west and a 2000 km northsouth transect. Within-site variation in feather isotope ratios was frequently larger than the difference predicted by gradients across West Africa. Thus, predicting the origin of individual feathers using single-isotope gradients was not reliable. The large within-site variability of feather isotope ratios of a habitat specialist species like the aquatic warbler indicates that using feather isotope ratios will require large sample sizes from many locations, and may thus not be an efficient tool in identifying wintering areas of Palaearctic African migrants.

The Aquatic Warbler Acrocephalus paludicola (AW) is the only globally threatened passerine species of continental Europe. The global population decreased by >90% during the 20th century. AWs breed in Palaearctic fen mires and sedge meadows and spend the non-breeding season in sub-Saharan Africa, but until 2007 no regular wintering site had been identified. To date, the only wintering grounds that have been discovered are in river floodplain marshes along the Senegal River in the Djoudj area, Senegal. Searches for additional wintering sites in south-western Mauritania, northern Senegal and Gambia have been unsuccessful. In Djoudj, AWs are found in extensive marshes dominated by Scirpus spp. or Sporobolus robustus, and favour shallow water and the occurrence of Eleocharis mutata and Sporobolus robustus on the microhabitat scale. Within these marshes, however, AW appear to avoid dense homogenous stands dominated by Scirpus maritimus. Estimates of the density of wintering AWs in suitable habitats range between 0.5 and 1.6 birds/ha. According to the estimated area of suitable habitat (4,000–10,000 ha with strong seasonal and inter-annual fluctuations), the Djoudj area may hold between 10 and >50% of the global population during the non-breeding season. Ringing, molecular studies and feather isotope ratios have failed to provide conclusive evidence for connectivity between the Djoudj area and particular Palaearctic breeding populations. Based on winter records, habitat data and satellite images, we speculate that the Inner Niger Delta in Mali could be another important wintering area. A pilot project that equipped 30 AWs in the Ukraine with geolocators in 2010 may reveal more details about migration routes and lead to the discovery of currently unknown wintering sites.

The globally threatened Aquatic Warbler Acrocephalus paludicola is an umbrella species for fen mires and is at risk of extinction in its westernmost breeding population due to severe habitat loss. We used boosted regression trees to model Aquatic Warbler habitat selection in order to make recommendations for effective management of the last remnant habitats. Habitat data were collected in the years 2004-2006 in all remaining breeding sites in Pomerania (eastern Germany and western Poland) as well as in recently abandoned sites. Models were validated using data from similar Aquatic Warbler habitats in Lithuania. The probability of occurrence of Aquatic Warblers in late May/early June was positively associated with low isolation from other occupied sites, less eutrophic conditions, a high proportion of area mown early in the preceding year, high availability of vegetation 60-70 cm high, high prey abundance and high habitat heterogeneity. Early summer land management is needed in the more productive sites to prevent habitat deterioration by succession to higher and denser vegetation. As this also poses a serious threat to broods, management that creates a mosaic of early and late used patches is recommended to preserve and restore productive Aquatic Warbler sites. In less productive sites, winter mowing can maintain suitable habitat conditions. Aquatic Warbler-friendly land use supports a variety of other threatened plant and animal species typical of fens and sedge meadows and can meet the economic interests of local land users.

The Aquatic Warbler (Acrocephalus paludicola) is a song bird breeding in fen mires and similarly structured other wetlands with a water depth of 1-10 cm. Widespread in central-European wetlands at the beginning of the 20th century, the species is now globally threatened. The westernmost and genetically distinct Pomeranian population is even on the verge of extinction. The major challenge in the conservation of remaining habitat is the cost- efficient removal of biomass. About 50% of the Pomeranian population survives in a valley fen near Rozwarowo in Northwest Poland, where between 1993 and 2007 a conspicuous change in breeding habitat has taken place from summer grazed sedge meadows to com- mercial winter cut reed beds. We compared vegetation structure, site conditions, and potential prey abundance with the distribution and abundance of Aquatic Warblers in Rozwarowo Marshes and studied temporal changes and the compatibility of conservation and reed cutting interests. Aquatic Warblers now occur almost exclusively in sparsely growing, low reed with abundant Thelypteris palustris, Carex elata, and Lysimachia vul- garis. This vegetation type provides more potential prey for Aquatic Warblers than the higher productive tall reed, whereas the patches of sedge vegetation have become too small following succession after abandonment. Currently, commercial reed cutting maintains suitable Aquatic Warbler breeding habitat. Considering the impending changes in the reed market, there is a need for flexible agri-environmental schemes (AES) to ensure that stripes are left uncut and to prevent eutrophication by high and long flooding of the site.

SUMMARYThe diversity and prevalence of malaria parasites of the genera Plasmodium and Haemoproteus were determined in the globally-threatened Aquatic Warbler Acrocephalus paludicola. Birds were sampled during migration in Portugal and at the wintering quarters in Senegal and parasites were detected using molecular methods. Only three generalist parasite lineages (Plasmodium) were found. There were no significant differences in the prevalence of parasites between sexes in Europe, but adults had higher prevalence than first-year birds, and birds in Europe had higher prevalence than those captured in Africa. When comparing with other Acrocephalus species and taking sample size into account, Aquatic Warblers had the lowest prevalence and, together with another threatened species, the Seychelles Warbler Acrocephalus sechellensis, the lowest diversity of malaria parasites. We hypothesize that the low diversity of parasites and absence of specialist lineages of Aquatic Warblers are caused by its small population size and fragmented distribution. Furthermore, Aquatic Warblers’ extreme habitat specialization may decrease their exposure to malaria parasites, but other explanations such as high mortality (which would constraint the sampling of infected birds) or, in contrast, very efficient immunological system in clearing the infections cannot be ruled out. This study contributes to explain variation in prevalence and diversity of malaria parasites among hosts.

Understanding the links between breeding and wintering areas of migratory species has important ecological and conservation implications. Recently, stable isotope technology has been used to further our understanding. Stable isotope ratios vary geographically with a range of biogeochemical factors and isotope profiles in organisms reflect those in their food and environment. For inert tissues like feathers, isotope profiles reflect the environment in which they were formed. Following large-scale habitat destruction, the globally threatened aquatic warbler Acrocephalus paludicola has a fragmented breeding population across central Europe, largely in Belarus, Poland and Ukraine. The species' sub-Saharan African wintering grounds have not yet been discovered, and this significantly hampers conservation efforts. Aquatic warblers grow their flight feathers on their wintering grounds, and we analysed stable isotope ratios (delta(15)N, delta(13)C, delta D) in rectrices of adults from six main breeding sites (subpopulations) across Europe to determine whether different breeding subpopulations formed a single mixed population on the wintering grounds. delta(15)N varies considerably with dietary trophic level and environmental factors, and delta D with the delta D in rainfall; neither varied between aquatic warbler subpopulations. Uniform feather delta(15)N signatures suggest no major variation in dietary trophic level during feather formation. High variance and inter-annual differences in mean delta D values hinder interpretation of these data. Significant differences in mean delta(13)C ratios existed between subpopulations. We discuss possible interpretations of this result, and consider differences in moulting latitude of different subpopulations to be the most parsimonious. delta(13)C in plants and animals decreases with latitude, along a steep gradient in sub-Saharan Africa. Birds from the most northwesterly breeding subpopulation (Karsibor, Poland) had significantly lower variance in delta(13)C and delta(15)N than birds from all other sites, suggesting either that birds from Karsibor are less geographically dispersed during moult, or moult in an area with less isotopic heterogeneity. Mean delta(13)C signatures from winter-grown feathers of different subpopulations were positively correlated with the latitude and longitude of breeding sites, suggesting a strong relationship between European breeding and African winter moulting latitudes. The use of stable isotopes provides novel insights into migratory connectivity and migration patterns in this little-known threatened species.

Knowledge of population-specific non-breeding areas in sub-Saharan Africa for the globally threatened Aquatic Warbler Acrocephalus paludicola is paramount for the implementation of successful conservation strategies that consider the species' entire annual range. This may be the case especially for declining marginal populations. Here we report on two Aquatic Warblers that were ringed in the Inner Niger Delta in Mali and in the region of the Djoudj National Park, Senegal. The first was recaptured in the Supoj mire, Ukraine, and the second observed in the Biebrza marshes in Poland. These records represent the first proof of connectivity between wintering areas and breeding sites for the species.

The globally-threatened Aquatic Warbler (Acrocephalus paludicola) breeds in Europe and spends the northern winter in sub-Saharan West Africa. We attached 30 geolocators to breeding birds in the central Ukraine in 2010. Three geolocators which collected data from the autumn migration were recovered in 2011. They revealed a previously-unknown migration route via southern Europe to stopover sites in south-western France and Spain. In West Africa, one bird spent some time well south of known non-breeding areas. For the conservation of some Aquatic Warbler populations, protection of hitherto unknown stopover sites in southern Europe and Africa may be crucial.

Der jungste Stand der Ausbreitung der Beutelmeise an ihrer nordwestlichen Verbreitungsgrenze und die Entwicklung der letzten Jahrzehnte wird beschrieben und die Verbreitung in Abb. 1–3 fur die Zeitraume bis 1965, 1966–1975 und 1976–1985 dargestellt. Die Verbreitungsgrenze verschob sich demnach von ca. 1930 bis 1965 um etwa 300 km nach W, kam zwischen 1965 und 1975 bis auf die Besiedlung Sudschwedens beinahe zum Stehen, um sich dann bis 1985 noch einmal sprunghaft um ca. 250 km nach W und fast 200 km nach N zu verschieben. Die nordlichsten Brutplatze liegen z. Z. bei Stockholm, die westlichsten in den Niederlanden. Der Brutbestand, der in brutenden ♀ angegeben wird, wird 1985 fur die Bundesrepublik Deutschland auf 310–340 und fur Sudskandinavien und Danemark auf 100–160 ♀ geschatzt. Die Besiedlung des Areals verlief in regional sehr unterschiedlichen Schuben. Eine gewisse Abhangigkeit zwischen starkeren herbstlichen Einflugen und Ansiedlungswellen in den darauffolgenden Fruhjahren konnte festgestellt werden. Die Zugwege und Winterquartiere haben sich ebenfalls schrittweise nach W verschoben. Der Bruterfolg in den neubesiedelten Arealen im westlichen Mitteleuropa ist wahrscheinlich (noch) zu gering, um die Populationen hier dauerhaft ohne Nachschub aus ostlichen Gebieten stabil zu halten. Verschiedene mogliche Ursachen der Ausbreitung werden diskutiert. Die Dispersionsdynamik der Art spielt offenbar eine wichtige Rolle. Als Anhang ist ein Verzeichnis der den Verf. bekannten Nistplatze in der Bundesrepublik Deutschland sowie eine umfangreiche Artbibliographie mit Schwerpunkt Mitteleuropa beigefugt.