Versatility of male Curlews Numenius arquata preying upon Nereis diversicolor::deploying contrasting capture modes dependent on prey availability

Curlews Numenius arquata use 2 methods to capture ragworms Nereis diversicolor they search for worms at the surface, which are taken with a single peck (called Npeck) and/or they search for visual cues, such as burrow entrances, and probe deep to extract the worm from the burrow (called Nprobe) Itis argued that male curlews select predominantly active worms, which are either grazing at the surface (Npeck) or are filter feeding within their burrows (Nprobe and sometimes Npeck). Profitability (mg S-' handling) increases with worm length and is greater for NPeck, because of its shorter handling time, than for NP,,&. Worms of both prey types I ca 6 cm are ignored, since profitability is below the intake rate (mg S-' feeding). During low water there is a shift from Nprobe to Npeck, which can be explained by changes in feeding behaviour of the worms. Nprobe, common in summer, disappears during autumn due to the increase of burrow depth (with the corresponding decrease of worms accessible as Nprobe), and to a reduction in filter feeding of the worm, which means that fewer traces are visible. Curlew search rate increases if, relatively, many prey are of the Nperk type. There appears to be a tradeoff between search rate and probab~lity of detection of conspicuous Npeck and cryptic Nprobe. NO evidence was found that curlews ignore one prey type and selectively search for the other We conclude that (1) unprofitable prey sizes are ignored, (2) the greater part of the profitable prey are not available. being hidden in the substrate and n~ostly not accessible even when detectable, (3) curlews continuously readjust their capture technique to changes in the available food supply

Seasonal trend in burrow depth and tidal variation in feeding activity of Nereis diversicolor

Ragworms Nereis diversicolor live in burrows which, if deeper than 5 to 10 cm, offer a safe refuge from most of their predators. Burrow depth must be ca 15 cm before they live out of reach of all predators. Burrow depth increases with body slze, levelling off at ca 15 cm, when the depth refuge is reached. Worms live at greater depths in sand than In mud, but this effect disappears if worms with identical body condition (expressed as deviation from mean body weight for a given body length) are compared. Seasonal variation in burrow depth is correlated with sea temperature and to a lesser extent with day length and body condition. Feeding worms are present near or at the surface. Fllter feeding occurs in the first 2 h after exposure (at least if a water film still remains at the surface) and surface feeding begins after that. The total time spent at the surface does not exceed an average of 50 s per tidal cycle. Feeding must be an extremely risky activity, because predators readily catch most N. diversicolor while present near or at the surface

Temporal and spatial accretion patterns and the impact of livestock grazing in a restored coastal salt marsh

A summer polder had developed a deficit in surface elevation of about 20 cm in respect to rising sea level during its almost one-hundred-year period of embankment. We addressed the questions whether the distance of the restored site to the intertidal flats and continuation of livestock grazing in the restored site could hamper surface-elevation change during the first 10 years after de-embankment of the summer polder. The surface-elevation change showed similar positive linear relationships with annual tidal flooding in both the reference salt marsh and the restored site, indicating that the surface-elevation change in the restored site was not moderated by the distance from the sea. The surface-elevation change had a clear seasonal pattern with positive values in winter and negative values during summer. The surface-elevation change was 11 mm/year in the grazed reference salt marsh and 7 mm/year in the grazed restored site, but amounted to 17 mm/year in ungrazed exclosures in the restored site, showing that grazing retarded the catching up of the elevation deficit in the restored site. The surface-elevation change within the restored site was higher close to the constructed creeks indicating the inception of levee formation. The surface-elevation change was also positively affected by the proximity of breaches in the embankment, but this effect was less clear than the effect of creeks. We conclude that the surface-elevation deficit may be compensated in the Wadden Sea summer polders by their de-embankment when sediment supply is high, whereas livestock grazing retards this process. Dug creeks increase spatial variation in the restored site.</p

Rotation grazing as a conservation management tool:Vegetation changes after six years of application in a salt marsh ecosystem

Grazing is commonly used in conservation to promote biodiversity, but the search for a grazing management regime that optimises biodiversity is still ongoing. Rotation grazing, where grazing is followed by a relatively long period of non-grazing, is a relative new tool in conservation management, and empirical studies on its effects on biodiversity are scarce. In this study, we tested for the effects of this rotation grazing on vegetation in comparison with more traditional regimes. We used a grazing experiment on the salt marsh of Noord-Friesland Buitendijks, The Netherlands, where we determined the effect of three rotation cycles (6 years; one year summer grazing with 1 cattle ha(-1) alternated with an ungrazed year) on species richness, temporal turnover and composition in comparison with more traditional regimes of summer grazing with horses and cattle at two densities (0.5 and 1 animal ha(-1)): We also determined the change in cover of two species of specific concern, Aster tripolium (an important host plant for pollinators) and Elytrigia atherica (an invasive dominant species). After six years, species richness increased in all grazing regimes, but less in rotation than in grazing with 1 horse or 1 cattle ha(-1). Species turnover was similar across all grazing regimes. Species composition in rotation differed from compositions in 1 cattle and 1 horse ha(-1). The increase in cover of A. tripolium was lower under rotation than grazing with 0.5 cattle ha(-1), but not different to the other regimes. Change in cover of E. atherica did not significantly differ across regimes, and showed a trend of increase in the ungrazed regime only. Hence, we found that the effects of rotation grazing on vegetation are relatively similar to the grazing regimes with cattle or horses in low densities. The implementation of this rotation regime over the more traditional regimes remains to be decided by the conservation body, depending on its applicability in terms of available grazing areas and livestock, as well as overall conservation goals

Behaviour of horses and cattle at two stocking densities in a coastal salt marsh

Livestock grazing has been practiced in salt marshes in the Wadden Sea area since 600 B.C. Currently livestock grazing is also applied for conservation management. However, effects of such grazing management on salt marshes are likely to vary depending on the species of livestock and stocking density due to differences in the behaviour of the animals. Yet, little is known about the behaviour of different livestock species and stocking densities grazing in salt marshes. We studied the grazing behaviour of horses and cattle by focal observation in an experiment with four different grazing treatments on a coastal salt marsh. In all treatments we recorded diet choice, movement and grazing activity, and spatial distribution. Livestock species shared an overlap in diet choice. Yet, horses more often foraged on the short grass Puccinellia maritima, while the cattle diet contained a higher amount of Aster tripolium. Horses travelled longer distances per day and spent more time grazing than cattle. Spatial distribution of cattle was significantly clustered, while horses showed a random distribution utilizing the whole area. Animal behaviour differs between livestock species and stocking densities with respect to diet choice, activity and spatial distribution

Physical properties analysis of uv-crosslinked sulfonated Poly Ether Ether Ketone and Methyl Cellulose / Nordiana Nabilla Ramly … [et al.]

Proton exchange membrane materials based on sulfonated Poly Ether Ether Ketone with Methyl Cellulose are developed in this study. The hybrid membrane is exposed to UV radiation with photoinitiator to improve the membrane dimensional stability up to 50%. The hybrid membranes characterized by FTIR shows the crosslinking occurs by formation of C-C bond from BEE instead of the consumption of SO3H group. This new crosslinked hybrid membrane shows good prospect for the use as proton exchange membrane in fuel cell

Klimaatverandering, verhoogde overstromingsrisico’s en kwelderbroedvogels [Climate change, tidal flooding risks and breeding shorebirds]

Het gaat slecht met veel vogels die in de Waddenzee broeden. Naast directe invloeden van menselijke activiteiten wordt vermoed dat klimaatverandering daarbij een belangrijke rol speelt. In dit artikel belichten we één aspect van klimaatverandering waarvan de gevolgen de laatste jaren al merkbaar zijn, namelijk het vaker optreden van overstromingen van nesten in buitendijkse broedgebieden. Lage kwelders vormen‘s zomers belangrijke broedgebieden: in hoeverre beïnvloedt een toenemend overstromingsrisico de levensvatbaarheid van vogelpopulaties, of kunnen vogels hun nestkeuze aanpassen aan deveranderende omstandigheden? Zou uitbreiding van kwelderareaal kunnen leiden tot het creëren van een ‘ecologische fuik’ voor vogels en zijn er maatregelen denkbaar om de overstromingsrisico’s voor kwelderbroedvogels tegen te gaan? [English] Climate change, tidal flooding risks and breeding shorebirds Bird populations are declining in the Wadden Sea. The contribution of climate change has been understudied, but recent evidence suggests that increased flooding frequencies during the breeding season are already affecting bird populations that breed on salt marshes. These effects are expected to get worse in the near future if birds do not adapt their nest-site selection, suggesting that the importance of low-lying breeding areas for shorebirds could decline substantially in the coming decades. The crucial question now is to what extent birds may adapt their habitat selection to the changing environment. Although several studies suggest that the adaptive potential of birds to more frequent flooding events is limited, this is based on anecdotal evidence and systematic long-term studies are now needed. Furthermore, such studies will inform us about the factors that constrain birds from selecting higher nest sites (vegetation, food, predators), such that efficient management strategies may be identified

Effects of grazing management on biodiversity across trophic levels–The importance of livestock species and stocking density in salt marshes

European coastal salt marshes are important for the conservation of numerous species of specialist plants, invertebrates, breeding and migratory birds. When these marshes are managed for nature conservation purposes, livestock grazing is often used to counter the dominance of the tall grass Elytrigia atherica, and the subsequent decline in plant species richness. However, it remains unclear what is the optimal choice of livestock species and stocking density to benefit biodiversity of various trophic levels. To fill this knowledge gap, we set up a triplicate, full factorial grazing experiment with cattle and horse grazing at low and high stocking densities (0.5 or 1 animal ha−1) at the mainland coast of the Dutch Wadden Sea. Here, we present the results after 4 years and integrate these with previously published results from the same experiment to assess effects of livestock grazing on various trophic groups. Stocking density affected almost all measured variables: high stocking densities favoured plant species richness and suppression of E. atherica, whereas low stocking densities favoured abundances of voles, pollinators and flowers. Densities of different functional groups of birds showed no significant response to the regimes, but tended to be somewhat higher under 0.5 horse and 1 cattle ha−1. Choice of livestock species had fewer and smaller effects than stocking density. Horse grazing was detrimental to vole density, and showed an interactive effect with stocking density for Asteraceae flower abundance. Multidiversity, a synthetic whole-ecosystem biodiversity measure, did not differ among regimes. These results are discussed in the light of other results from the same experiment. Because of these contrasting effects on different trophic groups, we advise concurrent application of different grazing regimes within a spatial mosaic, with the inclusion of long-term abandonment. High density horse grazing, however, is detrimental to biodiversity