Strong decrease of migrating Red-spotted Bluethroats Luscinia svecica svecica on Helgoland

Im Vergleich zu Schilderungen aus dem 19. Jahrhundert und überlieferten Daten aus der ersten Hälfte des 20. Jahrhunderts haben Rotsternige Blaukehlchen als Durchzügler auf Helgoland sehr stark abgenommen. In den letzten Jahrzehnten ist der Rückgang stärker als der Durchschnitt anderer durch Mitteleuropa nach Afrika ziehenden Singvogelarten. Während der Wegzug inzwischen fast völlig erloschen ist, erscheinen Heimzügler heute in kleiner Zahl. Es wird vermutet, dass heute weniger skandinavische Blaukehlchen eine südsüdwestliche Zugrichtung einschlagen, möglicherweise im Zusammenhang mit dem Verschwinden einer langflügeligen Population in Süd-Norwegen. Ob dafür Gründe in Brut-, Durchzugs- oder Überwinterungsgebieten verantwortlich sind, ist unklar. Das einst regelmäßige und heute so gut wie erloschene Auftreten von nach S-SW ziehenden Blaukehlchen wurde im Frühjahr offenbar schon immer von Einflügen der Südostzieher überlagert. Diese Frühjahrseinflüge gibt es noch heute, erreichen jedoch bei weitem nicht das Niveau früherer Zeiten. Die Mediane von Heim- und Wegzug liegen in neuerer Zeit später als in der ersten Hälfte des 20. Jahrhunderts. Weißsternige Blaukehlchen L. s. cyanecula sind erheblich seltener als die Nominatform und erscheinen auf dem Heimzug deutlich früher (vor allem März/April).Compared to descriptions from the 19th century and data from the first half of the 20th century, Red-spotted Bluethroats have considerably decreased as migrants on the island of Helgoland (southeastern North Sea). At least in the last decades this decline was stronger than the average of other long-distance migrating passerines passing Central Europe. Nowadays, only very few birds are recorded during fall migration, and spring migrants are observed and trapped in much lower numbers than in earlier decades. Presumably, fewer Scandinavian Bluethroats follow a S-SW route in autumn, perhaps in connection with the disappeareance of a long-winged population in southern Norway. It is not known whether the decline is based on impacts acting in the breeding area, on the migration route or in the winter quarter. The once regular, but today nearly extinct occurrence of S-SW migrating Bluethroats seems to have always overlapped with spring influxes of SE migrating birds. Such spring influxes do still occur, but nowadays on a lower level. In recent decades, the median dates of both spring and fall migration are delayed compared to the first half of the 20th century. White-spotted Bluethroats L. s. cyanecula are much scarcer than nominate birds and in spring occur much earlier (especially in March and April)

Phenology of the "visible bird migration" across the German Bight

Im Rahmen eines vom Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit geförderten Projekts zu Auswirkungen von Offshore-Windenergieanlagen auf den Vogelzug wurden vom Herbst 2003 bis Ende 2006 Vogelzugplanbeobachtungen in der Deutschen Bucht durchgeführt. Die Sichtbeobachtungen ziehender Vogelarten über See (Seawatching) und über dem Land (Islandwatching) erfolgten tagsüber mit etablierten Methoden an den drei Standorten Sylt, Helgoland und Wangerooge. Der besondere Wert der Studie liegt in der synoptischen Beobachtung an drei Standorten zumindest während der Zugzeiten. Von wenigen Ausnahmen abgesehen wurde beim Seawatching an allen drei Standorten und bei fast allen Arten in den Morgenstunden der stärkste Zug bemerkt, mittags und abends war die Zugintensität deutlich geringer. Unterschiede zwischen den Stationen bestanden vor allem in der Zusammensetzung der dominierenden Arten, was vor allem auf die unterschiedliche Lage von Brut- und Rastgebieten zurückzuführen ist, wodurch die Vögel die drei Stationen auf dem Zug mehr oder weniger stark tangierten (besonders auffällig bei den Gänsen). Beim Seawatching in den ersten drei Morgenstunden konnten insgesamt 185 Arten, davon 154 bei Sylt, 137 bei Helgoland und 148 bei Wangerooge registriert werden. Für 23 Arten, die besonders häufig auftraten bzw. die hinsichtlich der Gefährdung durch Offshore-Windenergieanlagen als kritisch gelten, werden jahres- und tageszeitliche Muster der Zugintensität geschildert und grafisch dargestellt, die beobachteten Truppgrößen für 11 Arten und die Zugintensität im Tagesverlauf für 15 Arten. Bei vielen Arten war bei Sylt der Wegzug und bei Wangerooge der Heimzug stärker ausgeprägt, während für Helgoland ein ausgeglichenes Verhältnis zwischen den beiden Zugperioden typisch war. In beiden Jahreszeiten war die tägliche Zugintensität zwischen den drei Stationen hochsignifikant korreliert und zwar sowohl bezogen auf die gesamte Zugintensität aller Arten als auch auf die vieler einzelner Arten. Auch wenn aufgrund der Lage von Brut- und Überwinterungsgebieten im Bereich der Deutschen Bucht vor allem mit Zug entlang einer SW-NE-Achse gerechnet werden muss, wurde dies beim Seawatching nur auf Helgoland festgestellt. Bei Sylt und Wangerooge zogen die meisten Vögel entlang der Küstenlinie, d. h. entlang einer S‑N- Achse bzw. einer W‑E-Achse. Beim Islandwatching in den ersten drei Morgenstunden wurden insgesamt 189 Arten beobachtet, davon 165 über Sylt, 133 über Helgoland und 161 über Wangerooge. Ebenfalls für 23 häufigere Arten wird die Phänologie beschrieben und grafisch dargestellt, die Truppgrößen für 10 Arten. Auch beim Islandwatching war die Zugintensität über Helgoland deutlich geringer als über den beiden küstennahen Inseln, mit etwa gleichstarkem Aufkommen zu beiden Zugperioden. Küstennah galt für vielen Arten, dass sie als Folge des von den meisten Singvogelarten gezeigten Leitlinienzuges über Wangerooge vor allem auf dem Heimzug und über Sylt vor allem während des Wegzuges beobachtet wurden: Während nur vergleichsweise wenige Individuen über Sylt (Herbst) bzw. Wangerooge (Frühjahr) auf See hinaus flogen, folgte die große Mehrheit der Vögel der Küstenlinie nach S (Sylt im Herbst) bzw. nach O (Wangerooge im Frühjahr). Offensichtlich scheuten sich Landvögel tagsüber vor dem Zug auf das offene Meer hinaus und folgten stattdessen der Küste. Die demzufolge wenigen von See ankommenden Vögel bedingten daher eine geringe Zugintensität im Frühjahr über Sylt bzw. im Herbst über Wangerooge. Nur für Helgoland konnte die in Mitteleuropa vorherrschende SW-NE-Richtung des Zuges bestätigt werden. Doch selbst dort hatten anscheinend bereits die Hafenmolen eine Leitlinienwirkung, denn im Herbst zogen zahlreiche Singvögel nach SE und S ab. Die starken Leitlinienwirkungen von Wangerooge (Frühjahr) und Sylt (Herbst) sorgten dafür, dass die den Zug über das offene Meer widerspiegelnden Standorte (Helgoland und Ankunft Sylt im Frühjahr bzw. Helgoland und Ankunft Wangerooge im Herbst) sowohl für alle Arten gemeinsam als auch bei Betrachtung einzelner Arten jeweils am engsten miteinander in Beziehung standen.Within a project supported by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety dealing with possible consequences of offshore wind farms on bird migration observations of migrating birds were carried out on three islands in the German Bight, Sylt, Helgoland and Wangerooge, from autumn 2003 to the end of 2006. With “seawatching” the migration of mostly larger species (waterbirds in the broadest sense) over the sea was recorded and “islandwatching” concentrated on the migration of smaller species (mostly passerines) over land (islands in this case). The particular goal of this study is the synoptic observation at three locations at least during the migration periods. Apart from some exceptions, at all three sites seawatching showed the highest migration intensity in the morning hours, much less migration occurred at midday and in the evening. Varying proportions of species are mainly caused by the different breeding and staging/wintering areas, whereby the three sites are touched by the birds to a greater or lesser extent. This phenomenon is most obvious in geese. With seawatching in the first three hours after sunrise a total of 185 species was recorded (154 near Sylt, 137 near Helgoland and 148 near Wangerooge). For 23 species, which were abundant or are regarded to be critical concerning effects of offshore wind turbines, the seasonal and daily patterns of migration intensity are described and shown in graphs, diurnal variation of migration intensity for 15 species and flock size for 11 species. In many species, migration was more intense near Sylt in autumn and near Wangerooge in spring, whereas a more balanced relation of the two migration periods was typical for Helgoland. During both seasons the daily migration intensity of the three sites was highly significantly correlated. That holds true for the overall picture of all species as well as for the migration intensities of many particular species. Due to the geographical locations of the breeding and wintering areas of most species, a general direction of migration along a SW-NE-axis can be expected. However, the results of seawatching could prove this only for Helgoland. Near Sylt and Wangerooge, most birds followed the coastline, i.e. they migrated along a S‑N-axis and W‑E-axis, respectively. With islandwatching in the first three hours after sunrise a total of 189 species was observed (165 above Sylt, 133 above Helgoland and 161 above Wangerooge). Phenology are described and presented graphically for 23 relatively abundant species, flock size for 10 species. As with seawatching, migration intensity was lower at Helgoland than at the two coastal islands and showed roughly the same amount of birds during spring and autumn migration. As a consequence of the preference of most passerines to migrate along a leading line, migration was stronger for many species in autumn at Sylt and more pronounced in spring at Wangerooge: While relatively few birds headed towards the sea at Sylt (autumn) and Wangerooge (spring), the great majority of birds followed the coastline southward (Sylt in autumn) and eastward (Wangerooge in spring), respectively. Obviously, passerines avoided to fly towards the open sea during daytime and followed the coastline instead. Hence, the few birds arriving from sea produced low migration intensities at Sylt in spring and at Wangerooge in autumn. The SW-NE-direction predominating in bird migration in Central Europe was only approved at Helgoland. But even there, jetties of the harbour acted as leading lines, because in autumn many passerines left the island towards SE and S. Because of the leading line effects at Wangerooge (spring) and Sylt (autumn) the connection was strongest between the sites representing migration over sea, i.e. between Helgoland and arrivals above Sylt in spring, but between Helgoland and arrivals above Wangerooge in autumn. This held true for all species together as well as for the single species

Model-based assessment of marine bird population status using monitoring of breeding productivity and abundance

Vertebrate populations are often monitored as part of broader assessments of ecosystem status, where they are expected to provide information on the ability of the ecosystem to support higher-level predators. However, because many vertebrates are long-lived and often only subsets of their populations can be monitored, abundance may not be sufficiently responsive to ecosystem status to provide early warnings of impending changes. Marine birds are often used as indicators of ecosystem status but, due to their long lifespan and delayed recruitment to the breeding population, changes in abundance are generally slow and often difficult to interpret. Their breeding productivity is, however, also widely monitored and much more responsive to ecosystem status, but the relevance of variation in productivity may be difficult to assess. We propose a model-based indicator that integrates monitoring of abundance and breeding productivity through demographic matrix models. The metric of the proposed indicator is the expected population growth rate, given the observed level of breeding productivity. This expected growth rate is then compared with a threshold derived from the criteria employed for red-listing of threatened species by the International Union for the Conservation of Nature. We demonstrate the suggested approach using data from Black-legged Kittiwakes Rissa tridactyla in the Greater North Sea region, Northwest Europe. The proposed indicator shows that the current level of breeding productivity is expected to lead to a population decline of 3–4% per year, which is equivalent to a red-list status as Endangered for the species in this region. Our indicator approach is used in OSPAR’s Quality Status Report 2023 and is expected to be used by European Union member states for reporting under the Marine Strategy Framework Directive in 2024. Our approach represents a major step forward in assessing the status of marine bird populations; the ideal next step would be to develop a coherent Integrated Population Modelling (IPM) framework that would allow inclusion of all data on population abundance and demography collected across the large and diverse marine ecosystems involved. breeding success, indicator, Marine Strategy Framework Directive, seabirds.acceptedVersio

Climate change in the Baltic Sea region : a summary

Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge of the effects of global warming on past and future changes in climate of the Baltic Sea region is summarised and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focuses on the atmosphere, land, cryosphere, ocean, sediments, and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in palaeo-, historical, and future regional climate research, we find that the main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, for Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution, and new scenario simulations with improved models, for example, for glaciers, lake ice, and marine food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth system have been studied, and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication, and climate change. New datasets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal timescales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first palaeoclimate simulations regionalised for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA), and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics are dominated by tides, the Baltic Sea is characterised by brackish water, a perennial vertical stratification in the southern subbasins, and a seasonal sea ice cover in the northern subbasins.Peer reviewe

ReSurveyGermany: Vegetation-plot time-series over the past hundred years in Germany

Vegetation-plot resurvey data are a main source of information on terrestrial biodiversity change, with records reaching back more than one century. Although more and more data from re-sampled plots have been published, there is not yet a comprehensive open-access dataset available for analysis. Here, we compiled and harmonised vegetation-plot resurvey data from Germany covering almost 100 years. We show the distribution of the plot data in space, time and across habitat types of the European Nature Information System (EUNIS). In addition, we include metadata on geographic location, plot size and vegetation structure. The data allow temporal biodiversity change to be assessed at the community scale, reaching back further into the past than most comparable data yet available. They also enable tracking changes in the incidence and distribution of individual species across Germany. In summary, the data come at a level of detail that holds promise for broadening our understanding of the mechanisms and drivers behind plant diversity change over the last century

Bücherschau

Besprochen werden 35 überwiegend deutschsprachige Neuerscheinungen aus den Bereichen Pflanzensoziologie / Geobotanik und Nachbargebiete

Bücherschau

Besprochen werden 29 Publikationen, überwiegend mit dem Erscheinungsjahr 1989, zu Pflanzensoziologie, Geobotanik und verwandten Gebieten

Bücherschau

Besprochen werden 44 geobotanische bzw. für Geobotaniker relevante Publikationen, die - von wenigen Ausnahmen abgesehen in deutscher Sprache - überwiegend in den Jahren 1991 und 1992 erschienen sind

Bücherschau

Im Rahmen der Bücherschau werden 34 überwiegend 1988 und 1989 erschienene Titel rezensiert

Feeding ecology of dunlins Calidris alpina staging in the southern Baltic Sea 2. Spatial and temporal variations in the harvestable fraction of favourite prey Hediste diversicolor.

Abstract The feeding habits of migrating dunlins Calidris alpina staging in different non-tidal coastal habitats in the southern Baltic Sea are described. The study also focuses on the structure of the benthic macrofauna of these habitats and the diet choice of dunlins. All investigations were carried out on Langenwerder Island (Wismar Bay), where different types of flats and beaches harbour a total of 30 to 40 species of marine macrofauna. The composition of the macrobenthos differed considerably between the eulittoral sandbank, the eulittoral mudflat, the pebble beach, and the sublittoral surroundings. Most dunlins were observed foraging in flocks of up to several hundred individuals on the eulittoral flats. Densities of up to 20 to 30 foraging dunlins ha 1 occurred annually during peak migration in September and October. Macrobenthos biomass in these habitats fluctuated between 20 and 40 g AFDM m 2 . The mean total food consumption of dunlins during autumn migration was estimated at 0.01 g AFDM m 2 d 1 . The predation pressure could be estimated at 3 to 6% of the suitable food supply. Dunlins staging on Langenwerder were able to attain a pre-migratory mass gain of 0.2 to 0.5% of their body weight per day within an 8 to 12-h daily feeding period. The birds fed predominantly on the polychaete Hediste diversicolor by probing. They selected small 7 to 31-mm-long individuals. When water levels were high, and the eulittoral flats inundated, many dunlins switched to foraging along the shorelines where a variety of small prey were taken from spilled macrophytes. Dunlins sometimes obviously ignored their most important food H. diversicolor, although available, by feeding on other prey such as juvenile fishes and shrimps, dipteran larvae or spilled amphipods. When feeding on amphipods, dunlins selected the smallest individuals