Occurrence of rats and their impacts on colonial waterbirds in a Danish fjord

Human development around the globe has led to great expansion of the Brown Rat (Rattus norvegicus), which has implications for local wildlife and especially ground-breeding birds. In this study, we analyse the colonisation and persistence of rats on small islets important to breeding waterbirds in a Danish fjord, and investigate the effect of rat presence on the number of breeding pairs of eight waterbird species. The islets had an annual rat colonisation probability of 6% and an annual rat population persistence rate of 65% (equalling an annual population survival rate of 62% when adjusting for re-colonisations upon extinctions). Contrary to our hypotheses, rat colonisation and persistence was uncorrelated with islet size, distance from the mainland and the presence of shrub cover. Rat presence had a significant negative effect on the number of breeding pairs of four waterbird species, including Avocet (Recurvirostra avosetta, reduced to 30% compared to years without rats), Black-headed Gull (Chroicocephalus ridibundus, reduced to 45%) and Common Tern (Sterna hirundo, reduced to 52%). The smaller bird species in particular seemed to be affected by the presence of rats, and control efforts aimed at reducing rat presence on important breeding bird islets may consequently have a positive effect on the occurrence and breeding success of these species. We found no evidence of birds acting on a memory of where rats had been present in the previous year, and further research is needed to investigate the precise mechanisms behind the recorded negative effects in the contemporary year, i.e. how do prospecting as well as settled breeders detect and behaviourally respond to the presence of rats

Effects of capture and marking on the behaviour of moulting Pink-footed Geese Anser brachyrhynchus on Svalbard

Tracking of individuals is increasingly being used in waterfowl research. However, the effects of capture and tags on waterfowl welfare and ecology are poorly understood and too rarely reported. In this paper, time budget data are used to investigate the behavioural effects of capture and marking on moulting and brood-rearing Pink-footed Geese Anser brachyrhynchus on their arctic breeding grounds. The study compares the prevalence of self-maintenance and foraging time for unringed/uncaptured birds, male birds marked with standard neck collars and female birds marked with heavier GPS collars, and reports on the reduction through time in the pecking behaviour directed towards these markers. Results indicate that capture and marking substantially altered behaviour of marked birds in the days immediately after capture, but also that this effect faded quickly and was not discernible six days after marking. Proportions of time spent preening during foraging bouts indicated that, in the first six days, GPS-collared birds were significantly more affected (time preening c. 12%) than birds ringed with standard neck collars (c. 3%). Both groups showed higher proportions of self-maintenance type behaviours than unringed birds of the same sex (time preening < 1%). The probability of an individual goose pecking its marker during an observation period was initially high for GPS-collared birds (c. 65%), but decreased substantially to reach c. 2% by 11 days after capture. Our study indicates that, after an initial period of discomfort, neck collars and GPS collars are suitable for studying the behaviour of individual geese

Seasonality of eelgrass biomass across gradients in temperature and latitude

Eelgrass Zostera marina L. meadows are major structural and trophic components of coastal ecosystems. The role of eelgrass in ecosystem functioning depends on biomass and production of the meadows, which can fluctuate greatly during an annual cycle and be major temporal drivers of changes in the coastal zone. We analysed magnitude and seasonality of eelgrass aboveground biomass, shoot density and production across temperature and latitude gradients over the majority of the species' distributional range, and investigated to what extent temperature and/or light drive differences in these values. Eelgrass phenology (timing of peak biomass, start and end of the growing season) showed strong effects of temperature and latitude, indicating that seasonality was considerably advanced in warm areas at low latitudes compared to cold areas at high latitudes. Magnitude of peak aboveground biomass, length of the growing season, mean annual shoot density and aboveground production did not change significantly with either temperature or latitude, indicating that these parameters were controlled mainly by other factors. Annual variation in aboveground biomass and shoot density was significantly smaller in areas with low summer temperature, indicating that while warm-water populations may show substantial temporal variation in biomass, cold-water meadows are less dynamic. These findings were supported by cold-water populations having a larger mean annual biomass and a greater investment in belowground parts. In all significant regressions, temperature was a better predictor of population dynamics than latitude. This indicates that eelgrass phenology might advance considerably in response to global warming, and suggests that the distributional range of this species might be moving northwards. Given the key role of eelgrass in coastal ecosystems, these climateinduced changes might entail substantial impacts on waterbirds, fish, invertebrates and other organisms exploiting these meadows. © Inter-Research 2014.Peer Reviewe

Measuring neck collar loss of Pink-footed Geese <i>Anser brachyrhynchus</i>

<div><p><b>Capsule</b> 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.</p></div

Using airborne lidar to characterize North European terrestrial high‐dark‐diversity habitats

Abstract A key aspect of nature conservation is knowledge of which aspects of nature to conserve or restore to favor the characteristic diversity of plants in a given area. Here, we used a large plant dataset with >40 000 plots combined with airborne laser scanning (lidar) data to reveal the local characteristics of habitats having a high plant dark diversity—that is, absence of suitable species—at national extent (>43 000 km2). Such habitats have potential for reaching high realized diversity levels and hence are important in a conservation context. We calculated 10 different lidar based metrics (both terrain and vegetation structure) and combined these with seven different field‐based measures (soil chemistry and species indicators). We then used Integrated Nested Laplace Approximation for modelling plant dark diversity across 33 North European habitat types (open landscapes and forests) selected by the European communities to be important. In open habitat types high‐dark‐diversity habitats had relatively low pH, high nitrogen content, tall homogenous vegetation, and overall relatively homogenous terrains (high terrain openness) although with a rather high degree of local microtopographical variations. High‐dark‐diversity habitats in forests had relatively tall vegetation, few natural‐forest indicators, low potential solar radiation input and a low cover of small woody plants. Our results highlight important vegetation, terrain‐ and soil‐related factors that managers and policymakers should be aware of in conservation and restoration projects to ensure a natural plant diversity, for example low nutrient loads, natural microtopography and possibly also open forests with old‐growth elements such as dead wood and rot attacks

Eelgrass (<i>Zostera marina</i>) Food Web Structure in Different Environmental Settings

<div><p>This study compares the structure of eelgrass (<i>Zostera marina</i> 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.</p></div

The relative (%) species contribution to total fish biomass (AFDW m^-2) in Dalby Bay (DB) and Kertinge Nor (KN) in June 2011.

<p>The relative (%) species contribution to total fish biomass (AFDW m^-2) in Dalby Bay (DB) and Kertinge Nor (KN) in June 2011.</p

Map and photos of the study areas on Funen Island, Denmark.

<p>Hatched areas indicate the studied eelgrass meadows in Dalby Bay (55°31ʹ07ʺ N, 10°37ʹ05ʺ E) and Kertinge Nor (55°26ʹ52ʺ N, 10°33ʹ30ʺ E) while photos illustrate differences in filamentous macroalgae, eelgrass shoot density, and jellyfish abundance. Encircled M shows location of monitoring stations for water column data. Contains data from the Map 10 data set of the Danish Geodata Agency, 2015.</p

<i>Zostera marina</i> meadow characteristics in Dalby Bay and Kertinge Nor.

<p>Values are mean ± SE. Asterisks indicate statistical significant differences based on t-tests (* = 0.05, *** = 0.001). For stacked columns the statistics refer to the summed value. (A) <i>Z</i>. <i>marina</i> and algal biomass. Numbers in columns are above to below ground biomass ratios. (B) <i>Z</i>. <i>marina</i> shoot density and leaf area index. (C) <i>Z</i>. <i>marina</i> above ground production.</p

Biomass distribution at trophic levels of <i>Zostera marina</i> meadows in Dalby Bay and Kertinge Nor, Denmark, June 2011.

<p>The biomass of each species is distributed across trophic levels (TL) 1–4 according to their diet, based on stable isotope mixing model results (Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146479#pone.0146479.t005" target="_blank">5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146479#pone.0146479.t006" target="_blank">6</a>), gut contents (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146479#pone.0146479.s003" target="_blank">S3 Table</a>), and literature data (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146479#pone.0146479.s004" target="_blank">S4 Table</a>). Combined width of bars indicate biomass at each TL in (A) Dalby Bay and (B) Kertinge Nor. Note biomass value of TL1 in KN is divided by 5 for visual purposes. (C) Linear regression of TL 2–4 and log₁₀biomass (DB: log₁₀biomass = 1.416–0.374×TL, R² = 0.99; KN: log₁₀biomass = 0.683 + 0.017×TL, R² = 0.24), with slope indicating overall shape of the consumer part of biomass pyramids in Fig 6A and 6B above.</p