Kevin Kuhlmann Clausen

Grazing management can counteract the impacts of climate change-induced sea level rise on salt marsh-dependent waterbirds

Summary Climate change–induced rises in sea level threaten to drastically reduce the areal extent of important salt marsh habitats for large numbers of waterfowl and waders. Furthermore, recent changes in management practice have rendered existent salt marshes unfavourable to many birds, as lack of grazing has induced an increase in high-sward communities on former good-quality marshes. Based on a high-resolution digital elevation model and two scenarios for projected rise in near-future sea levels, we employ an ArcMap allocation model to foresee the areal loss in salt marsh associated with these changes. In addition, we quantify the areal extent of inadequate salt marsh management in four EU Special Protection Areas for Birds, and demonstrate concurrent population dynamics in four species relying on managed habitats. We conclude by investigating potential compensation for climate change–induced salt marsh losses by means of more efficient management. Our models indicate that by the end of this century 15·3–43·6% of existent salt marshes will be flooded due to rising sea levels, and that inadequate managed salt marsh presently makes up around 51·1% of total marshes. Thus, re-establishing extensive areas of well-managed marshes might counterbalance the loss expected from rising sea levels during the next century. In addition to positive effects on plant diversity, this will benefit energetically challenged herbivorous waterfowl such as light-bellied brent geese Branta bernicla hrota L. and increase potential recovery of wader populations with unfavourable conservation status such as black-tailed godwit Limosa limosa L., dunlin Calidris alpina L. and ruff Philomachus pugnax L. Synthesis and applications. Implementing environmentally friendly management schemes based on extensive grazing (around 1 cow per hectare) is an important initiative to counteract the accelerating climate change–induced habitat loss in near-coastal areas across the globe, and to secure priority salt marsh habitats that support internationally important populations of breeding, wintering and staging waterfowl. However, this may only be a temporary solution that will have to be supplemented by increased reintegration with the sea and managed retreat of seawalls or near-coastal agricultural areas to effectively safeguard the future salt marsh biome.

Effects of neckbands on body condition of migratory geese

AbstractRinging and marking are widely used techniques in avian ecology to assist studies of migration, survival and behaviour, and often used to estimate population sizes. Only rarely, however, have the effects of these markings on bird viability been thoroughly tested. Using an abdominal profile index of marked geese and body mass of recaptured birds previously marked, this study investigated the effect of neckbands on body condition of Pink-footed Geese Anser brachyrhynchus at different temporal scales, and evaluated to what extent capture, handling and banding affected these birds on short, medium and longer terms. Our results indicated that body condition of geese were negatively affected in the days immediately succeeding capture, but that only a minor effect persisted on a seasonal scale. We found no support for a long-term effect of neckbands on the body mass of individual birds, indicating that the capture and handling event might be the main contributory cause to the transitory decline in body condition. Pink-footed Geese thus seemed to habituate almost completely to the presence of neckbands, and the effects on long-term body condition can be expected to be minor. However, neckbands might still influence important life-history traits such as reproduction and survival by means of, e.g., altering social interactions, increasing predation or interfering with mate acquisition.ZusammenfassungDer Einfluss von Halsringen auf die Körperkondition ziehender Gänse In der Ökologie der Vögel sind Beringung und Markierung vielfach genutzte Techniken bei der Erforschung des Vogelzuges sowie von Überlebensraten und Verhaltensweisen; außerdem werden sie oft zur Schätzung von Populationsgrößen eingesetzt. Trotzdem wird der Einfluss dieser Markierungen auf die Überlebensfähigkeit der Vögel nur selten sorgfältig überprüft. Mittels eines Abdominalprofil-Index markierter Gänse in Verbindung mit Körpermassedaten von zu einem früheren Zeitpunkt beringten Wiederfängen untersuchten wir in dieser Studie den Einfluss von Halsringen auf die Körperkondition von Kurzschnabelgänsen Anser brachyrhynchus über verschiedene Zeiträume und ermittelten, in welchem Ausmaß Fang, Bearbeitung und Beringung die Vögel kurz-, mittel- und langfristig beeinträchtigten. Unsere Ergebnisse weisen darauf hin, dass die Körperkondition der Gänse in den direkt auf den Fang folgenden Tagen negativ beeinflusst wurde, allerdings nur geringfügige Effekte die Saison über andauerten. Wir fanden keine Belege für einen Langzeiteffekt der Halsringe auf die Körpermasse einzelner Vögel, was dafür spricht, dass das Fang- und Bearbeitungsereignis die Hauptursache für die vorübergehende Abnahme der Körperkondition darstellen könnte. Kurzschnabelgänse scheinen sich somit fast vollständig an das Vorhandensein der Halsringe zu gewöhnen, und die langfristigen Auswirkungen auf die Körperkondition sind als gering anzunehmen. Allerdings könnten Halsringe dennoch wichtige biologische Größen wie zum Beispiel Reproduktion und Überlebensrate beeinflussen, indem sie beispielsweise soziale Interaktionen verändern, das Prädationsrisiko erhöhen oder in die Partnerwahl eingreifen.

Eelgrass (Zostera marina) Food Web Structure in Different Environmental Settings

This study compares the structure of eelgrass (Zostera marina L.) meadows and associated food webs in two eelgrass habitats in Denmark, differing in exposure, connection to the open sea, nutrient enrichment and water transparency. Meadow structure strongly reflected the environmental conditions in each habitat. The eutrophicated, protected site had higher biomass of filamentous algae, lower eelgrass biomass and shoot density, longer and narrower leaves, and higher above to below ground biomass ratio compared to the less nutrient-enriched and more exposed site. The faunal community composition and food web structure also differed markedly between sites with the eutrophicated, enclosed site having higher biomass of consumers and less complex food web. These relationships resulted in a column shaped biomass distribution of the consumers at the eutrophicated site whereas the less nutrient-rich site showed a pyramidal biomass distribution of consumers coupled with a more diverse consumer community. The differences in meadow and food web structure of the two seagrass habitats, suggest how physical setting may shape ecosystem response and resilience to anthropogenic pressure. We encourage larger, replicated studies to further disentangle the effects of different environmental variables on seagrass food web structure.

Carry-Over or Compensation? The Impact of Winter Harshness and Post-Winter Body Condition on Spring-Fattening in a Migratory Goose Species

Environmental conditions at one point of the annual cycle of migratory species may lead to cross-seasonal effects affecting fitness in subsequent seasons. Based on a long-term mark-resighting dataset and scoring of body condition in an arctic breeding goose species, we demonstrate a substantial effect of winter harshness on post-winter body condition. However, this effect was compensated along the spring migration corridor, and did not persist long enough to influence future reproduction. This highlights the importance of temporal scale when assessing impacts of environmental effects, and suggests a state-dependent physiological mechanism adjusting energy accumulation according to internal energy stores carried into spring. In support of these findings, the development of body condition was unaffected by whether geese used supplementary feeding sites or not. While there was no effect of winter harshness on the average population pre-breeding body condition, individual variations in early spring body condition (probably related to different life-histories) were partly traceable throughout spring. This strongly indicates a carry-over effect on the individual level, possibly related to differences in dominance, site use, disturbance or migration strategy, which may potentially affect future reproduction.

Current and Potential Threats to Nordic Duck Populations — A Horizon Scanning Exercise

We review the current and future threats to duck populations that breed, stage, moult and/or winter in the Nordic countries. Migratory duck species are sensitive indicators of their changing environment, and their societal value confirms the need to translate signals from changes in their distribution, status and abundance into a better understanding of changes occurring in their wetland environments. We used expert opinion to highlight 25 major areas of anthropogenic change (and touch briefly on potential mitigation measures through nature restoration and reserve management projects) that we consider key issues likely to influence Nordic duck populations now and in the near future to stimulate debate, discussion and further research. We believe such reviews are essential in contributing to development of successful management policy as well as stimulating specific research to support the maintenance of duck species in favourable future conservation status in the face of multiple population pressures and drivers.

Seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios from hunter-based surveys

AbstractDemographic monitoring is vital for tracking and modelling the population dynamics of highly mobile bird populations. However, different types of monitoring can sometimes lead to different outcomes, and understanding the causes of equivocal results is an important step to advance future monitoring schemes. This study found consistent seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios among Danish hunter-based wing surveys, and describes how accounting for this variation might explain reported discrepancies between this and other monitoring methods. Early season flocks were dominated by adult males, and juvenile proportions were highest in November and significantly lower before and after this peak. Nationwide field assessments undertaken in January 2012 showed no significant differences from sex and age ratios in the wing survey data from that particular hunting season (2011/2012), indicating that this survey is a good predictor of Wigeon demography. These results highlight the need to account for consistent temporal variation in such demographic time series when using the results to model population parameters.ZusammenfassungJahreszeitliche Schwankungen in Geschlechterverhältnis und Altersstruktur bei der Eurasischen Pfeifente (Anas penelope) anhand von Erhebungen durch Jäger Für die Nachverfolgung und Modellierung populationsdynamischer Prozesse ist bei hochmobilen Vogelpopulationen ein demographisches Monitoring von entscheidender Bedeutung. Unterschiedliche Arten des Monitorings können jedoch gelegentlich zu unterschiedlichen Resultaten führen, und das Verständnis der Ursachen von mehrdeutigen Ergebnissen ist ein wichtiger Schritt in der Entwicklung zukünftiger Monitoring-Systeme. In den Erhebungen dänischer Jäger fanden sich durchgängig jahreszeitliche Schwankungen im Geschlechterverhältnis und in der Altersstruktur der Eurasischen Pfeifente (Anas penelope); diese Studie beschreibt, wie die Berücksichtigung solcher Unterschiede eventuell die Diskrepanzen zwischen den Ergebnissen aus unterschiedlichen Monitoring-Methoden erklären könnte. Schwärme zu Beginn der Saison wurden von adulten Männchen dominiert, während der Anteil junger Vögel im November am höchsten und vor und nach diesem Spitzenwert signifikant niedriger war. Im Januar 2012 landesweit durchgeführte Freiland-Bewertungen zeigten keine signifikanten Unterschiede im Geschlechterund Altersverhältnis zu den Erhebungen dieser speziellen Jagdsaison (2011/2012), was nahelegt, dass eine solche Erhebung ein guter Prädiktor für demographische Aussagen bei Pfeifenten ist. Diese Ergebnisse unterstreichen die Notwendigkeit, konsistente zeitliche Schwankungen in derartigen demographischen Zeitreihen zu berücksichtigen, wenn die Ergebnisse dazu benutzt werden, Populationsmerkmale zu modellieren.

Measuring neck collar loss of Pink-footed Geese Anser brachyrhynchus

Capsule The ability to estimate mark loss of ringed animals is important to assess demographic parameters from mark-recapture studies correctly. Based on 23 years of neck collar recovery data from the Svalbard breeding population of Pink-footed Geese, we estimate an overall average annual loss rate of 3.2%. Neck collar loss was similar between males and females, and did not (based on currently available data) differ significantly between two types of collars used.

Highly dynamic wintering strategies in migratory geese: Coping with environmental change

Abstract When and where to move is a fundamental decision to migratory birds, and the fitness‐related costs and benefits of migratory choices make them subject to strong selective forces. Site use and migration routes are outcomes of opportunities in the surrounding landscape, and the optimal migration strategy may be conservative or explorative depending on the variability in the environment occupied by the species. This study applies 25 years of resighting data to examine development in winter migration strategy of pink‐footed geese divided among Denmark, the Netherlands and Belgium, and analyse potential drivers of strategy change as well as individuals’ likelihood to break with migratory tradition. Contrary with the general notion that geese are highly traditional in their winter site use, our results reveal that winter migration strategy is highly dynamic in this species, with an average annual probability of changing strategy of 54%. Strategy was not related to hunting pressure or winter temperature, but could be partly explained by a tracking of food resources in a landscape of rapid land use changes. The probability of individuals changing strategy from year to year varied considerably between birds, and was partly related to sex and age, with young males being the most likely to change. The annual probability of changing wintering strategy increased substantially from ≈40% to ≈60% during the study period, indicating an increasingly explorative behaviour. Our findings demonstrate that individual winter strategies are very flexible and able to change over time, suggesting that phenotypic plasticity and cultural transmission are important drivers of strategy choice in this species. Growing benefits from exploratory behaviours, including the ability to track rapid land use changes, may ultimately result in increased resilience to global change.

Using dark diversity and plant characteristics to guide conservation and restoration

Summary 1.Dark diversity is a promising concept for prioritising management efforts as it focuses on species that are present in the regional pool, but locally absent even though environmental requirements are met. Currently, we lack knowledge of what characterises species belonging to the dark diversity more often than others, although this is important knowledge for restoration and conservation actions. 2.We applied the concept to a massive national (Danish) plant diversity database, containing 236,923 records from 15,160 surveys involving 564 species. This enabled the first geographically comprehensive (43,000 km2) assessment of dark diversity, at a spatial resolution relevant for conservation and restoration planning (78 m2) across multiple terrestrial habitats, thereby maximising the practical applications of this concept. The probability for a given plant species to belong to the dark diversity was computed and logistically regressed against variables representing its ecological preferences (e.g. nutrient availability), strategies (competitor, stress tolerant, ruderal), mycorrhizal relationships, establishment capacities (seed mass) and dispersal abilities. 3.Forty-six percent of the species had a high probability (>95%) of being part of dark diversity, whereas for 7% of the species this probability was less than 60%. 4.Typical dark diversity plants tended to depend on mycorrhiza, were mostly adapted to low light and low nutrient levels, had poor dispersal abilities and were ruderals and stress intolerant. 5.Synthesis and applications. Characterising species that are more often absent from suitable sites than others (dark diversity species) has important implications for the planning and management of natural ecosystems. From our study, practitioners gain insight into the factors triggering the absence of individual plant species in a seemingly suitable habitat. We highlight the need to carefully consider mycorrhizal inoculations with a suitable assemblage of fungi to promote the establishment success of dark diversity plants. Additionally, time lags in plant species dispersal and establishment as well as spatial connectivity in fragmented habitats are central to consider in nature management although assisted migration might also aid poor dispersers. Finally, nutrient-poor localities are probably important “islets” allowing nitrophobic dark diversity plant species to thrive within agricultural landscapes that are generally nutrient rich. This article is protected by copyright. All rights reserved.

Dark diversity illuminates the dim side of conservation and restoration

1 Dark diversity is a promising concept for prioritizing management efforts as it focuses on missing species, i.e., species present in the regional pool, but locally absent despite suitable environmental conditions. 2 We applied the concept to a massive national plant diversity database (236,923 records from 15,160 surveys involving 564 species) to provide the first geographically comprehensive assessment of dark diversity across a large area (43,000 km2), at a spatial scale (~75 m2) relevant for conservation and restoration planning and across multiple terrestrial habitats, thus maximising its practical application potential. The likelihood for a given plant species to belong to the dark diversity pool was computed and logistically regressed against its ecological preferences (nutrient availability, pH etc.), strategies (competitor, stress tolerance, ruderal), mycorrhizal dependence and infection percentage, seed mass and maximum dispersal distance. 3 Forty-six percent of the species were absent in >95 % of the suitable sites, whereas 7 % of the species were absent in less than 60 % of sites that were deemed suitable. 4 Species that were more likely to belong to the dark diversity tended to depend on mycorrhiza, were mostly adapted to low light and nutrient levels, had poor dispersal abilities, were ruderals and had a low stress tolerance. Synthesis and applications Our findings have important implications for the planning and management of natural ecosystems requiring detailed knowledge of what triggers the presence/absence of individual plant species in a seemingly suitable habitat. We conclude that practitioners may need to carefully consider mycorrhizal inoculations with a suitable assemblage of fungi for certain plant species to become established. Also assisted migration might be necessary to help poor dispersers although spatial and temporal processes are also important to have in mind. Finally, it is important to vary nutrient loads making room for plant species to colonise both nutrient-poor and nutrient-rich localities.