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Capsule Context-specific equations are needed to reconstruct diet composition and intake rate of Red Knots by the use of shell fragments retrieved from droppings.Aims To explore whether the method to reconstruct Red Knot diet described by Dekinga & Piersma [Dekinga, A. & Piersma, T. 1993. Reconstructing diet composition on the basis of faeces in a mollusc-eating wader, the Knot Calidris canutus. Bird Study 40: 144–156] accurately predicts the diet of Red Knots Calidris canutus canutus outside Northwest Europe, at Banc d'Arguin, Mauritania.Methods Feeding experiments with captive Red Knots on the bivalves Dosinia isocardia or Loripes lucinalis were carried out at Banc d'Arguin, the main wintering area of Red Knot subspecies C. c. canutus. Ingested diets were compared with the reconstructed diets derived from the general method developed by Dekinga & Piersma (1993). Droppings collected over multiple years were also analysed to evaluate the calibration method from this study.Results Of the total ingested shell mass (DMshell) in both bivalves, approximately 65% of the shell mass was retrieved in the droppings (DMdrop). Therefore, dry mass of droppings in the field (DMdrop) has to be multiplied by 1.547 to calculate the ingested dry mass (DMshell). For size estimations of ingested shells from droppings, hinges should be used for D. isocardia and hinges including tops for L. lucinalis.Conclusion The correction factor of 1.547 found here is 50% larger than the factor 0.993 for heterodont bivalves from Europe established by Dekinga & Piersma (1993). Application of the published factor would lead to serious underestimation of energy intake rates based on dropping frequencies and dropping content (by as much as 35%), although it would have small effects on the relative species composition of the diet. Having shown that such correction factors can differ among sites and prey we recommend their determination in new ecological contexts.

Shorebirds at northern latitudes during the nonbreeding season typically carry relatively large lipid stores and exhibit an up-regulation of lean tissues associated with digestion and thermogenesis. Intraspecific variation in these tissues across sites primarily reflects differences in environmental conditions. Rock (Calidris ptilocnemis (Coues, 1873)) and Purple (Calidris maritima (Brünnich, 1764)) sandpipers are closely related species having the most northerly nonbreeding distributions among shorebirds, living at latitudes up to 61°N in Cook Inlet, Alaska, and up to ~71°N in northern Norway, respectively. Cook Inlet is the coldest known site used by nonbreeding shorebirds, and the region’s mudflats annually experience extensive coverage of foraging sites by sea and shore-fast ice. Accordingly, Rock Sandpipers increase their fat stores to nearly 20% of body mass during winter. In contrast, Purple Sandpipers exploit predictably ice-free rocky intertidal foraging sites and maintain low (<6.5%) fat stores. Rock Sandpipers increase the mass of lean tissues from fall to winter, including contour feathers, stomach, and liver components. They also have greater lean pectoralis and supracoracoideus muscle and liver and kidney tissues compared with Purple Sandpipers in winter. This demonstrates a combined emphasis on digestive processes and thermogenesis, whereas Purple Sandpipers primarily augment organs associated with digestive processes. The high winter fat loads and increased lean tissues of Rock Sandpipers in Cook Inlet reflect the region’s persistent cold and abundant but sporadically unavailable food resources.

Density dependence in vital rates is key to population regulation. Rather than being constant, the strength of density dependence may vary throughout the year, but empirical evidence is limited. Based on 22 years of data of color-banded birds from a recovering population of Eurasian Spoonbills Platalea leucorodia leucorodia, we show, for the first time, seasonal variation in density dependence in survival of a long-distance migrating bird. Combining resightings and dead recoveries at breeding, stopover, and nonbreeding areas enabled us to (1) separate true survival from permanent emigration from the breeding area, and (2) estimate survival in three seasons: summer, early winter (including autumn migration), and late winter (including spring migration). Accompanying the rapid population growth, juvenile annual survival initially increased, manifested in early winter, but thereafter, at high population sizes, it strongly decreased through a combination of decreasing survival in all seasons. Annual survival of subadult (second- and third-year) and adult birds decreased more gradually with increasing population size, with density dependence occurring in early winter for subadults and late winter for adults. Thus, the shape and strength of density dependence in survival varied with age and season. Understanding the seasonal timing of density dependence, especially with reference to underlying mechanisms, is important for the design of effective conservation strategies.

Closely related species or subspecies can exhibit metabolic differences that reflect site-specific environmental conditions. Whether such differences represent fixed traits or flexible adjustments to local conditions, however, is difficult to predict across taxa. The nominate race of Rock Sandpiper (Calidris ptilocnemis) exhibits the most northerly nonbreeding distribution of any shorebird in the North Pacific, being common during winter in cold, dark locations as far north as upper Cook Inlet, Alaska (61 degrees N). By contrast, the tschuktschorum subspecies migrates to sites ranging from about 59 degrees N to more benign locations as far south as similar to 37 degrees N. These distributional extremes exert contrasting energetic demands, and we measured common metabolic parameters in the two subspecies held under identical laboratory conditions to determine whether differences in these parameters are reflected by their nonbreeding life histories. Basal metabolic rate and thermal conductance did not differ between subspecies, and the subspecies had a similar metabolic response to temperatures below their thermoneutral zone. Relatively low thermal conductance values may, however, reflect intrinsic metabolic adaptations to northerly latitudes. In the absence of differences in basic metabolic parameters, the two subspecies' nonbreeding distributions will likely be more strongly influenced by adaptations to regional variation in ecological factors such as prey density, prey quality, and foraging habitat. Received 19 April 2012, accepted 4 September 2012.

Almost all accounts of the reproductive biology of House Martins Delichon urbicum are based on studies of birds breeding in artificial nests that are monitored every few days. Here, I provide a study on House Martins using self-built mud nests at a single colony in Gaast, The Netherlands (225 nest attempts in 2004-2011); the stages of breeding were inferred from 'remote' observations of parental and chick behaviour. Small chicks were noticed from 30 May onwards, with a first peak of nestling appearance in 5-9 June. A second, and larger, peak in small chicks occurred in late June. Large chicks from first broods were noticed from mid June to mid August, and the first large chicks from second broods from late July onward. The last fledglings left nests in late September. Among the 205 successful nest attempts, 62% had one brood, and 38% had two broods (three in one case). The first nest sites to be occupied in mid-April were always old nests that had survived the winter. Surprisingly, the use of old nests did not result in earlier incubation and chick-rearing activities. Nevertheless, re-used near-intact old nests hosted multiple broods in 72% of cases, a much higher percentage than in newly built nests (20%). The earlier occupation of old nests and the greater incidence of second broods was further associated with a relatively high percentage of older House Martins. Whereas only 8% of 126 nests hosting one brood were occupied by at least one known >2nd calendar year bird, no fewer than 30% of the 79 nests with two broods were. Despite a steady offering of clean wood-concrete nests at the colony, such artificial alternatives were occupied in only 23 out of 307 possible cases, rather than the near-100% occupancy of old mud nests and nest remains. Also, the start date of occupation was later than that of intact or partial old mud nests. This strong preference by old,er birds for (the remains of) existing mud nests and the rejection of clean, strong artificial nests, impl

In expanding populations, individuals may increasingly be forced to use sites of relatively low quality. This process, named the "buffer effect," was previously described for the Black-tailed Godwit (Limosa limosa islandica) in its use of nonbreeding sites in Great Britain and of breeding areas in Iceland. On the basis of diet analyses from droppings and stable isotopes, we describe a new case for the expanding French wintering population of the Black-tailed Godwit, an expansion accompanied by a drastic change in feeding strategy. In the 1990s, Black-tailed Godwits started using intertidal mudflats at Ile de Re, where they eat the rhizomes of seagrass (Zostera noltii) rather than the customary shellfish (Macoma balthica) eaten at both the preferred (initial) site (Aiguillon Bay) and the area occupied last (Yves to Marennes-Oleron bays). Individually color-marked godwits appeared faithful to both diet type and site, suggesting a cost of a change of strategy. This represents a first case of rhizome-feeding in shorebirds, and it exemplifies a case of carnivorous birds occupying a new site shifting to herbivory.

Resolving the migratory connectivity (identifying non-breeding grounds) of migrating bird populations that are morphologically similar is crucial for an understanding of their population dynamics and ultimately their conservation. Such is the case in Black-tailed Godwits Limosa limosa, where the Iceland-breeding subspecies islandica shows overlap during the non-breeding season with the continental-Europe-breeding limosa. On the basis of variation in the control region of mitochondrial DNA, it was already shown that there is a cleat geographic structure in their phylogeography and a clear discrimination between the haplotypes of the two subspecies. We can thus assign subspecies of non-breeding individuals on the basis of a molecular assay. Here we validated this approach using samples of 113 birds with known breeding origin, and on the basis of haplotype variation, all birds were properly assigned to each subspecies. We then tested for overlap during non-breeding season using a sample of 278 birds from an Iberian wintering and staging area, the inland rice fields in southwest Iberia (Extremadura, Spain). We showed that even in this inland area, 6.5 % of the birds belonged to islandica subspecies, thus demonstrating the usefulness of genetic markers as an alternative or supplementary method to the most common approach, individual colour-ringing.

In their African freshwater wintering habitats, shorebirds show a high prevalence of blood parasites, whereas no parasites are detected elsewhere along the migration route. We looked at two genera of haemosporidian parasites, Haemoproteus and Plasmodium, in the long-distance migrating Ruff (Philomachus pugnax) along a geographical/seasonal gradient to verify the infection pattern and examine possible hidden organ infections at European staging areas. We amplified parasite DNA from blood of 53 healthy birds wintering in Mali, 53 samples of seven organ tissues (spleen, liver, kidneys, heart, lungs, brain, and pectoral muscle) from healthy individuals caught during spring migration, and 18 weak birds found sick in summer in The Netherlands. We confirm that Ruffs wintering in Africa carried blood infections and that some infections developed into hidden organ infections during spring migration. Moreover, sick birds either had new infections (in one juvenile) or relapses (in an adult harboring an African lineage). Our results suggest that some parasites develop latency. This strategy may be beneficial for the parasite as it may take control over reappearance in the blood to help further transmission.

Increasing evidence shows that spatial interactions between sedentary organisms can structure communities and promote landscape complexity in many ecosystems. Here we tested the hypothesis that reef-forming mussels (Mytilus edulis L.), a dominant intertidal ecosystem engineer in the Wadden Sea, promote abundances of the burrowing bivalve Cerastoderma edule L. (cockle) in neighboring habitats at relatively long distances coastward from mussel beds. Field surveys within and around three mussel beds showed a peak in cockle densities at 50-100 m toward the coast from the mussel bed, while cockle abundances elsewhere in the study area were very low. Field transplantation of cockles showed higher survival of young cockles (2-3 years old) and increased spat fall coastward of the mussel bed compared to within the bed and to areas without mussels, whereas growth decreased within and coastward of the mussel bed. Our measurements suggest that the observed spatial patterns in cockle numbers resulted from (1) inhibition effects by the mussels close to the beds due to preemptive algal depletion and deteriorated sediment conditions and (2) facilitation effects by the mussels farther away from the beds due to reduction of wave energy. Our results imply that these spatial, scale-dependent interactions between reef-forming ecosystem engineers and surrounding communities of sedentary benthic organisms can be an important determinant of the large-scale community structure in intertidal ecosystems. Understanding this interplay between neighboring communities of sedentary species is therefore essential for effective conservation and restoration of soft-bottom intertidal communities.

Intensification of agricultural use of grassland habitats has been linked to the declines of many farmland bird species, several of whom have been in decline for multiple decades despite agri-environmental schemes. In the Netherlands, where most grasslands have been transformed into well-drained monocultures managed for maximal dairy production, schemes that aim to protect nests from agricultural activities are the most popular. The cause of the failure of these schemes, however, seems poor recruitment of farmland birds. Using the black-tailed godwit Limosa limosa limosa as our model species, we tested the hypothesis underlying the most popular agri-environmental schemes that there are no differences in condition at hatch, growth, and apparent survival rates between chicks raised on monocultures compared with chicks from herb-rich meadows with high water tables, often managed, for the sake of grassland birds, in traditional ways. We also compare the growth rates from both habitat types with those of chicks from dairy farmland from 1976 to 1985, a time when population declines of godwits first became visible. Hatchling mass did not differ between chicks from herb-rich meadows and grassland monocultures, but chicks hatched on monocultures were on average 1416% lighter at fledging, and had 4% smaller bills than chicks hatched on herb-rich meadows. The growth rates of female chicks hatched on herb-rich meadows were similar to those of chicks measured from 1976 to 1985. Males fledged lighter and smaller than females. Apparent survival during the first year of life for chicks hatched on herb-rich meadows was 2 center dot 5 times higher than that of chicks hatched on grassland monocultures. The apparent survival on herb-rich meadows seems sufficient for a stable population. Synthesis and applications: We found striking differences between chicks hatched on modern grassland monocultures and herb-rich meadows. That chicks hatched on monocultures had lower growth and survival

Foraging birds can manage time spent vigilant for predators by forming groups of various sizes. However, group size alone will not always reliably determine the optimal level of vigilance. For example, variation in predation risk or food quality between patches may also be influential. In a field setting, we assessed how simultaneous variation in predation risk and intake rate affects the relationship between vigilance and group size in foraging Ruddy Turnstones Arenaria interpres. We compared vigilance, measured as the number of head-ups' per unit time, in habitat types that differed greatly in prey energy content and proximity to cover from which predators could launch surprise attacks. Habitats closer to predator cover provided foragers with much higher potential net energy intake rates than habitats further from cover. Foragers formed larger and denser flocks on habitats closer to cover. Individual vigilance of foragers in all habitats declined with increasing flock size and increased with flock density. However, vigilance by foragers on habitats closer to cover was always higher for a given flock size than vigilance by foragers on habitats further from cover, and habitat remained an important predictor of vigilance in models including a range of potential confounding variables. Our results suggest that foraging Ruddy Turnstones can simultaneously assess information on group size and the general likelihood of predator attack when determining their vigilance contribution.

When populations grow or decline, habitat selection may change due to local density-dependent processes, such as site dependence and interference. In seasonally migrating animals, nonbreeding distributions may be determined through these mechanisms of density dependence, which we examine here at a hemispheric scale for a long-distance migrating bird. Using summer and winter resightings of 2,095 Eurasian spoonbills Platalea leucorodia leucorodia that were ringed in the Netherlands during 16 years of fast population growth, we show that neither site dependence nor interference fully explains their patterns of survival and winter distribution. Within their three main wintering areas, annual survival decreased with an increase in population size. While survival was consistently higher in the two European wintering areas (France, Iberia), most spoonbills migrated onward to winter in west Africa. The number of birds wintering in Europe increased, but not enough to maximize annual survival. We conclude that a constraint of tradition (their "migration tendency") inhibits birds from changing their migratory habits. We pose that this phenomenon may similarly constrain other migratory populations from rapidly responding to large-scale climate- and/or human-driven habitat changes at their wintering grounds.

When a diet switch results in a change in dietary isotopic values, isotope ratios of the consumer's tissues will change until a new equilibrium is reached. This change is generally best described by an exponential decay curve. Indeed, after a diet switch in captive red knot shorebirds (Calidris canutus islandica), the depletion of C-13 in both blood cells and plasma followed an exponential decay curve. Surprisingly, the diet switch with a dietary N-15/N-14 ratio (N-15) change from 11.4 to 8.8 parts per thousand had little effect on N-15 in the same tissues. The diet-plasma and diet-cellular discrimination factors of N-15 with the initial diet were very low (0.5 and 0.2 parts per thousand, respectively). N-15 in blood cells and plasma decreased linearly with increasing body mass, explaining about 40 % of the variation in N-15. N-15 in plasma also decreased with increasing body-mass change (r(2)=.07). This suggests that the unusual variation in N-15 with time after the diet switch was due to interferences with simultaneous changes in body-protein turnover.

The failure of animals to fit all life-cycle stages into an annual cycle could reduce the chances of successful breeding. In some cases, non-optimal strategies will be adopted in order to maintain the life-cycle within the scope of one year. We studied trade-offs made by a High Arctic migrant shorebird, the red knot Calidris canutus islandica, between reproduction and wing feather molt carried out in the non-breeding period in the Dutch Wadden Sea. We compared primary molt duration between birds undertaking the full migratory and breeding schedule with birds that forego breeding because they are young or are maintained in captivity. Molt duration was ca. 71 days in breeding adults, which was achieved by an accelerated feather replacement strategy. Second-year birds and captive adults took ca. 22% and 27% longer, respectively. Second-year birds start molt in late June, more than four weeks before captive adults, and almost seven weeks before adults that return from breeding in late July-August. Adults finish molt in October when steeply increasing thermostatic costs and reductions in food availability occur. Primary molt duration was longer in female than in male knots (all ages), which was accordance with the somewhat larger body size of females. Since fast growth leads to lower quality feathers, the speedy wing molt shown by Arctic-breeding birds may represent a time constraint that is an unavoidable and routine cost of reproduction. So far it was hypothesized that only birds over 1 kg would have difficulty fitting molt within a year. Here we show that in birds an order of magnitude smaller, temporal imperatives may impose the adoption of non-optimal life-cycle routines in the entire actively breeding population.

The determination of temporal niche dynamics under field conditions is an important component of a species' ecology. Recent developments in niche mapping, and the possibility to account for spatial autocorrelation in species distributions, hold promise for the statistical approach explored here. Using species counts from a landscape-scale benthic monitoring programme in the western Dutch Wadden Sea during 19972005 in combination with sediment characteristics and tidal height as explanatory variables, we statistically derive realised niches for two bivalves, two crustaceans and three polychaetes, encompassing predators, suspension and bottom feeding functional groups. Unsurprisingly, realized niches varied considerably between species. Intraspecific temporal variation was assessed as overlap between the year-specific niche and the overall mean niche, and this analysis revealed considerable variation between years. The main functional groups represented by these species showed idiosyncratic and wide variability through the study period. There were no strong associations between niche characteristics and mean abundance or body size. Our assessment of intraspecific niche variability has ramifications for species distribution models in general and offers advances from previous methods. 1) By assessing species' realized niches in the multivariate environmental space, analyses are independent from the relative availability of particular environments. Predicted realized niches present differences between years, rather than annual differences in environmental conditions. 2) Using spatially explicit models to predict species habitat preferences provide more precise and unbiased estimates of speciesenvironment relationships. 3) Current niche models assume constant niches, whereas we illustrate how much these can vary over only a few generations. This emphasizes the potentially limited scope of global change studies with forecasts based on single-time species distribution snaps

The Wadden Sea is a shallow coastal region, with a large area of sedimentary tidal flats that extends from The Netherlands to Denmark and has been declared a site of international importance in the Dutch and German parts (Ramsar status and UNESCO World Heritage Site). Benthic macrofauna are central to the ecosystem functioning of this area, as they recycle nutrients, decompose organic matter and are an important food source for many secondary consumers, like fish and waterbirds. Due to the environmental gradients characteristic of estuarine systems, it is expected that changes in assemblage composition will be observed across the physical and environmental gradients of the Wadden Sea. First, we explored the spatial variation in assemblage composition of benthic macrofauna across the intertidal part of the Dutch Wadden Sea using 3 years of biomass data. Then, we identified the relative importance of six environmental variables for explaining and predicting changes in assemblage composition across the intertidal areas of the Wadden Sea using generalised dissimilarity modelling (GDM). In accordance with the environmental gradients across this system, the biomass contributed by a few common species differed from west to east and were distinct in the Dollard. In the west, bivalves Mya arenaria, Cerastoderma edule and Ensis directus contributed a relatively large and equal share of the total biomass, whereas C edule contributed the sole largest share of the total biomass towards the east. The polychaete Alitta succinea became a large share of the total biomass in the upper Ems and in the Dollard estuary, but contributed little elsewhere. Similar to the observed differences in species composition, the spatial patterns in assemblage composition, as predicted by the GDM models, identified the Dollard as distinct and that the prevalence of assemblage types in the west differed to the east. Median grain size, followed by microphytobenthic biomass, and exposure time were the mo

Recently, Schroeder etal. (2010, Ibis 152: 368-377) suggested that intronic variation in the CHD1-Z gene of Black-tailed Godwits breeding in southwest Friesland, The Netherlands, correlated with fitness components. Here we re-examine this surprising result using an expanded dataset (2088 birds sampled from 2004 to 2010 vs. 284 birds from 2004 to 2007). We find that the presence of the Z* allele (9% of the birds) is not associated with breeding habitat type, egg size, adult survival, adult body mass or adult body condition. The results presented here, when used in synergy with the previously reported results by Schroeder etal., suggest that there might be a tendency towards female adults with the Z* allele laying earlier clutches than adult females without the Z* allele. The occurrence of the Z* allele was also associated with a higher chick body mass and return rate. Chicks with the Z* allele that had hatched early in the breeding season were heavier at birth than chicks without the Z* allele and chicks with the Z* allele that had hatched late. Collectively, the results suggest that variation in the CHD1-Z gene may indeed have arisen as a byproduct of selection acting on females during the egg fase and on chicks during the rearing stages of the reproductive cycle.

Mauritanian Spoonbills (Platalea leucorodia balsaci) only breed at Banc d'Arguin, Mauritania, West Africa. Their populations have declined; however, nothing is known about possible ecological factors involved, including their primary food and foraging habits. Home range sizes, habitat selection, and foraging rhythm in six adult Mauritanian Spoonbills were documented by attaching backpack harnesses with solar-powered satellite GPS-transmitters. Based on 18 bird-months of data (5,844 selected ground positions) collected between 2008 and 2010, these individuals never left the study area centered on the island of Tidra. The fixed kernel home range size was 23-101 km(2) ((x) over bar = 62 km(2)) and the core area 2-14 km(2) ((x) over bar = 7 km(2)). Home range sizes did not differ between breeding and non-breeding seasons. Mauritanian Spoonbills fed only in intertidal areas where they preferred the seagrass-covered (Zostera noltii) areas and they fed primarily during the ebbing tide. Furthermore, the GPS-positions away from the high tide roosts were strongly associated with creeks dissecting the seagrass beds. During the non-breeding season, foraging occurred throughout the 24-hr period, but during the breeding season they foraged exclusively by night. Received 30 July 2012, accepted 2 January 2013.

We carried out an observational and experimental study to decipher how resource characteristics, in interaction with the predator's phenotype, constrain a fitness-determining performance measure, i.e. refuelling in a migrant bird. Two subspecies of red knot (Calidris canutus rogersi and C. c. piersmai) use northern Bohai Bay, Yellow Sea, China, for the final prebreeding stopover, during their 10,000-15,000. km long migrations between wintering and breeding areas. Here, they feed on small bivalves, especially 2-7. mm long Potamocorbula laevis. With an average stay of 29 days, and the need to store 80 g of fat for the onward flights to high-Arctic breeding grounds, red knots need to refuel fast. Using existing knowledge, we expected them to achieve this on the basis of (1) prey with high flesh to shell mass ratios, (2) large gizzards to crush the ingested molluscs, or (3) a combination of the two. Rejecting all three predictions, we found that red knots staging in Bohai Bay had the smallest gizzards on record (4.9 +/- 0.8 g, mean +/- s.e.m., N=27), and also found that prey quality of P. laevis is much lower than predicted for the measured gizzard size (i.e. 1.3 rather than the predicted 4.5 kJ. g(-1) dry shell mass, DMshell). The estimated handling time of P. laevis (0.2 s) is much shorter than the observed time between two prey ingestions (0.7 s), indicating that prey handling time is no constraint. Based on field observations of dropping rates and on indoor digestion trails, the shell processing rate was estimated at 3.9 mg DMshell s(-1), i.e. three times higher the rate previously predicted for red knots eating as fast as they can with the measured gizzard size. This is explained by the small and easily crushed P. laevis enabling high processing rates. As P. laevis also occurred in high densities, the metabolizable energy intake rate of red knots with small gizzards at 5 J s(-1) was as high as at northward staging sites elsewhere in the world. Currently, therefore

Estimates of seasonal mortality for long-distance migrant birds are extremely challenging to collect and consequently reports are scarce. Determining when and where mortality occurs within the annual cycle is important for an understanding of population dynamics and the evolutionary drivers of long-distance migration. We collected data on seasonal survival in a mark-recapture study of colour-marked Red Knots Calidris canutus canutus in their main wintering area at tropical Banc d'Arguin, Mauritania, West Africa. Our study population breeds 9,000 km to the northeast on Taymyr Peninsula, central northern Siberia. Our results show that annual apparent survival decreased from 0.87 +/- A 0.01 (SE) in 2002-2005 to 0.78 +/- A 0.02 in 2006-2009. During the 3-year time-window between 2006 and 2009, additional resightings just before migration and after return to the wintering grounds allowed us to partition the year into two periods: the non-breeding period on the Banc d'Arguin, and the migration and breeding period away from it. We estimated that, on the Banc d'Arguin, the 2-month apparent survival rate was 0.94 +/- A 0.01, whereas 2-month survival approached unity during the rest of year. Hence, most mortality occurred on the tropical wintering grounds. We review the possible physiological and ecological stressors involved and discuss the generality of these results.

Refuelling by migratory birds before take-off on long flights is generally considered a two-phase process, with protein accumulation preceding rapid fat deposition. The first phase expresses the demands for a large digestive system for nutrient storage after shrinkage during previous flights, the second phase the demands for fat stores to fuel the subsequent flight. At the last staging site in northward migration, this process may include expression of selection pressures both en route to and after arrival at the breeding grounds, which remains unascertained. Here we investigated changes in body composition during refuelling of High Arctic breeding red knots (Calidris canutus piersmai) in the northern Yellow Sea, before their flight to the tundra. These red knots followed a three-phase fuel deposition pattern, with protein being stored in the first and last phases, and fat being deposited mainly in the second phase. Thus, they did not shrink nutritional organs before take-off, and even showed hypertrophy of the nutritional organs. These suggest the build up of strategic protein stores before departure to cope with a protein shortage upon arrival on the breeding grounds. Further comparative studies are warranted to examine the degree to which the deposition of stores by migrant birds generally reflects a balance between concurrent and upcoming environmental selection pressures.

The determination of temporal niche dynamics under field conditions is an important component of a species’ ecology. Recent developments in niche mapping, and the possibility to account for spatial autocorrelation in species distributions, hold promise for the statistical approach explored here. Using species counts from a landscape-scale benthic monitoring programme in the western Dutch Wadden Sea during 1997–2005 in combination with sediment characteristics and tidal height as explanatory variables, we statistically derive realised niches for two bivalves, two crustaceans and three polychaetes, encompassing predators, suspension and bottom feeding functional groups. Unsurprisingly, realized niches varied considerably between species. Intraspecific temporal variation was assessed as overlap between the year-specific niche and the overall mean niche, and this analysis revealed considerable variation between years. The main functional groups represented by these species showed idiosyncratic and wide variability through the study period. There were no strong associations between niche characteristics and mean abundance or body size. Our assessment of intraspecific niche variability has ramifications for species distribution models in general and offers advances from previous methods. 1) By assessing species’ realized niches in the multivariate environmental space, analyses are independent from the relative availability of particular environments. Predicted realized niches present differences between years, rather than annual differences in environmental conditions. 2) Using spatially explicit models to predict species habitat preferences provide more precise and unbiased estimates of species–environment relationships. 3) Current niche models assume constant niches, whereas we illustrate how much these can vary over only a few generations. This emphasizes the potentially limited scope of global change studies with forecasts based on single-time species distribution sna

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In recent decades, the NW Europe population of the nominate subspecies of the Black-tailed Godwit, Limosa limosa limosa, has been in steep decline. As no changes in survival have been apparent so far, these declines are likely to have been caused by declines in recruitment, possibly due to decreasing quality and availability of breeding habitat. Most nominate Black-tailed Godwits breed in agricultural grasslands in the Netherlands and, to some extent, in Germany. Here we show that, in contrast to the general decreasing trend, numbers of breeding pairs have actually increased at the southernmost limit of their distribution in France, from 51 pairs in 1985 to 164 pairs in 2011. We review current knowledge of this godwit population as a basis for a demographic study.

Advances in mowing schedules have led to early and rapid declines in the seasonal food availability for, and survival rates of, chicks of grassland-breeding waders. Concurrently, increased levels of soil fertilization may have improved food abundance for adults. These developments are assumed to have resulted in an advancement of laying during 1930-1976 in several meadowbird species, including Black-tailed Godwits. Despite an apparent selective advantage of early breeding, after 1976 Godwits stopped advancing their laying dates. We have analyzed the timing of breeding and reproductive investment in Dutch Black-tailed Godwits relative to recent changes in agricultural practices and climate during 1976-2007. Early and late spring temperatures and precipitation in March were used as indicators for the timing of fertilizer application and mowing, and also as qualitative measures of relative food availability for adults and chicks. When precipitation was higher in March, Black-tailed Godwits laid earlier. Following warmer winters, the earliest females laid larger eggs, which hatched heavier Chicks with a higher survival probability. We suggest that the positive effect of an increasing March precipitation on invertebrate abundance may be constrained by the current policy of rigid control of the water table. This policy prevents Godwits from further advancing laying dates, which would increase their chick's survival prospects under increasingly early mowing schedules. Policy-makers should, next to delaying mowing schedules, also consider reduced draining in early spring as a tool to help stop the population decline of the Black-tailed Godwit.

Foraging rate and the distribution of foragers depend on prey distribution in conjunction with interindividual interactions. Generalized functional response models predict intake rates and spatial distributions of foragers on the basis of resource distribution and interference competition. The adequacy of these models depends on how well they capture the foragers' essential behavior. In this paper, we report on the results of a foraging experiment designed to examine the mechanisms of interference competition using red knots Calidris canutus that feed on buried bivalves. Red knots are rarely observed to interfere in the field, but this does not imply absence of interference. Our experimental setup minimized resource depletion, which allowed us to quantify interference competition as the decline in intake rate as a function of group size, with prey density and social status as additional treatments. We found that intake rate and searching efficiency decreased with group size and that dominant birds had higher intake rates than subordinates. Additionally, time spent searching for prey increased with group size. The decrease in intake rate was not due to conventional interference mechanisms (such as kleptoparasitism and time spent interacting with conspecifics) but to "cryptic interference," that is, avoidance of physical encounters with conspecifics. To accurately predict intake rates and foraging distributions, theory and models need to account for the possibility that animals anticipate and try to avoid, at some costs, physical encounters with conspecifics (i.e., conflicts that would make conventional interference behavior visible).

Ecosystem engineers can strongly modify habitat structure and resource availability across space. In theory, this should alter the spatial distributions of trophically interacting species. In this article, we empirically investigated the importance of spatially extended habitat modification by reef-building bivalves in explaining the distribution of four avian predators and their benthic prey in the Wadden Sea-one of the world's largest intertidal soft-sediment ecosystems. We applied Structural Equation Modeling to identify important direct and indirect interactions between the different components of the system. We found strong spatial gradients in sediment properties into the surrounding area of mixed blue mussel (Mytilus edulis) and Pacific oyster (Crassostrea gigas) reefs, indicating large-scale (100s of m) engineering effects. The benthic community was significantly affected by these gradients, with the abundance of several important invertebrate prey species increasing with sediment organic matter and decreasing with distance to the reefs. Distance from the reef, sediment properties, and benthic food abundance simultaneously explained significant parts of the distribution of oystercatchers (Haematopus ostralegus), Eurasian curlews (Numenius arquata), and bar-tailed godwits (Limosa lapponica). The distribution of black-headed gulls (Chroicoceph ridibundus)-a versatile species with many diet options-appeared unaffected by the reefs. These results suggest that intertidal reef builders can affect consumer-resource dynamics far beyond their own boundaries, emphasizing their importance in intertidal soft-bottom ecosystems like the Wadden Sea.

Effects of predation may cascade down the food web. By alleviating interspecific competition among prey, predators may promote biodiversity, but the precise mechanisms of how predators alter competition have remained elusive. Here we report on a predator-exclosure experiment carried out in a tropical intertidal ecosystem, providing evidence for a three-level trophic cascade induced by predation by molluscivore Red Knots (Calidris canutus) that affects pore water biogeochemistry. In the exclosures the knots' favorite prey (Dosinia isocardia) became dominant and reduced the individual growth rate in an alternative prey (Loripes lucinalis). Dosinia, a suspension feeder, consumes suspended particulate organic matter (POM), whereas Loripes is a facultative mixotroph, partly living on metabolites produced by sulfur-oxidizing chemoautotrophic bacteria, but also consuming suspended POM. Reduced sulfide concentrations in the exclosures suggest that, without predation on Dosinia, stronger competition for suspended POM forces Loripes to rely on energy produced by endosymbiotic bacteria, thus leading to an enhanced uptake of sulfide from the surrounding pore water. As sulfide is toxic to most organisms, this competition-induced diet shift by Loripes may detoxify the environment, which in turn may facilitate other species. The inference that predators affect the toxicity of their environment via a multi-level trophic cascade is novel, but we believe it may be a general phenomenon in detritus-based ecosystems.

For a long time, agricultural areas had considerable ornithological value, an ecological richness which in The Netherlands was epitomised by the term 'meadow birds'. However, over the last half century, agricultural intensification has negatively affected the quality of meadow bird habitats. Here we provide a quantitative characterization of agricultural habitats and their use by Black-tailed Godwits Limosa I. limosa in the south-western part of the province of Friesland, The Netherlands, in 2009, to provide a yardstick to evaluate further change. We used groundwater level, vegetation typology, relief in the landscape, the occurrence of foot drains, land use and soil characteristics such as textures and peat to describe the landscape that comprised 43 polders covering 8480 ha. We used a Principal Component Analysis to summarize landscape characteristics and find that much of the habitat variation is explained by a combination of herb richness of the vegetation, the presence or absence of foot drains and groundwater level. The modern agricultural landscape of southwest Friesland consists of 80% of uniform, intensively managed landscape with herb-poor meadows and low groundwater levels, the remaining 20% being taken by remnants of the former herb-rich meadows. The whole study area was searched weekly and Black-tailed Godwits were mapped between arrival and egg-laying. The positive relationship between godwit density and the first PC axis indicates that Black-tailed Godwits preferred herb-rich polders with high groundwater levels and the presence of foot drains. Soil texture was poorly correlated with godwit breeding densities for intensively managed (herb-poor) parcels, but for herb-rich meadows, soils of sandy clay loam and sandy clay harboured the highest densities of godwits. To protect Black-tailed Godwits, areas should have a herb-rich vegetation, contain foot drains and high groundwater tables should be re-established.

In a southern Spanish population of the colonial-breeding Afrotropical migrant House Martins Delichon urbicum, a high overall prevalence of (molecularly assayed) haemosporidian infections (in the non-parasitological literature usually denoted with the inclusive term 'malaria') was associated with negative fitness consequences for individuals carrying single or double infections. To verify this in a northern population, we here report on the occurrence of malaria in 112 fledgling and 358 adult House Martins from The Netherlands. Repeatability of molecular essays was 94.4% (n = 125). Malaria was not found in any of the fledglings, but 77% of the adults carried single or double infections of two Haemoproteus haplotypes (Delurb1, Delurb2) and five Plasmodium haplotypes (GRW2, GRW9, GRW11, COLL6 and Turdus1). The two Haemoproteus and two of the Plasmodium haplotypes overlapped with nine haplotypes observed in Spain, with Dutch birds showing another four. Haemoproteus infections were common (occurring in 70% of adult samples) and Plasmodium was rare (9%). Molecularly sexed females with blood parasite infections tended towards a higher chance of double infection (33%) than males (23%). Of 64 cases of birds captured in successive years, 23% showed no change in infection status, 5% lost infection, and there was an 85% chance for adults to gain a 'malaria' type. Within a single breeding season, infection status did not change in 6 of 13 cases (46%). However, in 6 of the 7 cases of change (86%), there was loss of a Haemoproteus infection. Infection status did not correlate with body mass or body size, tail asymmetry, occurrence of louse flies, nor with the likelihood of recapture in the subsequent year. The limited evidence so far suggests that House Martins get infected away from the European breeding grounds.

Phenotypic flexibility allows animals to adjust their physiology to diverse environmental conditions encountered over the year. Examining how these varying traits covary gives insights into potential constraints or freedoms that may shape evolutionary trajectories. In this study, we examined relationships among haematocrit, baseline corticosterone concentration, constitutive immune function and basal metabolic rate in red knot Calidris canutus islandica individuals subjected to experimentally manipulated temperature treatments over an entire annual cycle. If covariation among traits is constrained, we predict consistent covariation within and among individuals. We further predict consistent correlations between physiological and metabolic traits if constraints underlie species-level patterns found along the slow-fast pace-of-life continuum. We found no consistent correlations among haematocrit, baseline corticosterone concentration, immune function and basal metabolic rate either within or among individuals. This provides no evidence for constraints limiting relationships among these measures of the cardiovascular, endocrine, immune and metabolic systems in individual red knots. Rather, our data suggest that knots are free to adjust individual parts of their physiology independently. This makes good sense if one places the animal within its ecological context where different aspects of the environment might put different pressures on different aspects of physiology.

The nomination of the Dutch and German parts of the Wadden Sea as a World Heritage Site within the framework of the World Heritage Convention (WHC) represents high-level recognition of the global importance of this area for millions of migratory birds. It was not the first accolade for the unique wilderness area, but arguably the most prestigious. In its nomination, the World Heritage Convention requests the two countries to strengthen cooperation within the African-Eurasian Flyways, a system of global connectedness by migrant waterbirds in which the Wadden Sea plays a vital role. Here we review the origin and (lack of) implementation of the international conservation instruments available to protect values that are easily undervalued and forgotten, instruments that involve cooperation along the flyway axes. We describe how scientific information sometimes helps governments to implement their obligations, but also how, in spite of indisputable scientific data, governments take decisions contrary to their obligations under international conservation instruments. In some cases such decisions are reversed after scientists have shown measurable declines in the global populations of the migratory waterbirds and established the causality of such declines. At a global level, a few more regional flyway conservation instruments may be needed, but for most parts of the world the instrumentation to secure the well-being of the flyways are in place. It boils down to the determination by governments, informed by good science and under close scrutiny by NGOs, to put them into concrete action.

Background: The ability to connect breeding, stopover and wintering locations of populations of migratory birds greatly enhances our understanding of the phenomenon of migration and improves our chances of effectively conserving these species. Among Palearctic-Afrotropical migratory species, aerial insectivores like the house martin (Delichon urbicum) are sensitive to factors influencing the availability of flying insects, and have declined in recent decades. The strict aerial behaviour of martins severely limits ring recoveries on wintering grounds and so there is a dearth of information on where European breeding populations over-winter in Africa, and the relative effects of population regulation on breeding vs. wintering grounds. We used a newly developed multi-isotope (delta H-2, delta C-13, delta N-15) feather isoscape for Africa together with inferences from summarized ring return data based on longitude, to assign winter origins to birds captured at a breeding colony in The Netherlands. Principal Findings: Based on isotopic analyses of winter-grown martin feathers, we used a likelihood-based assignment approach to describe potential wintering locations where molt occurred of individual house martins from a Dutch colony by assigning them to four potential isotopically distinct clusters in Africa. We found the overwhelming majority of Dutch martins were assigned to a geographical cluster associated with West Africa. Conclusions/Significance: The existence of strong isotopic gradients and patterns in African foodwebs that support migratory wildlife allows for the spatial assignment of tissues grown there. The assignment of Dutch house martins to wintering grounds primarily in West Africa was in strong agreement with independent and indirect methods used to infer winter origins of this species based on the association between the Normalized Difference Vegetation Index (NDVI) in Africa and population patterns in Italy and the United Kingdom. These confirmato

Piersma T., van der Velde M., El-Hacen E.M., Lok T. & Overdijk O. 2012. Molecular verification of the subspecies status of the Mauritanian Spoonbill Plata lea leucorodia balsaci. Ardea 100: 131-136. In 1974 R. de Naurois and F. Roux proposed that the distinct morphology of Eurasian Spoonbills Plata lea leucorodia breeding on offshore islands in the Banc d'Arguin, Mauritania, in comparison with the sympatrically wintering northwest European breeding Spoonbills Plata lea leucorodia leucorodia, justifies recognition as a separate subspecies Plata lea leucorodia balsaci. This proposal is examined here on the basis of variation in nuclear DNA, microsatellites identified earlier for P minor and P ajaja. We show that there is significant variation between Spoonbills breeding in Mauritania (n = 25) and the sympatrically wintering conspecifics breeding in the Dutch Wadden Sea (n = 105). Of the total genetic variation among the 130 individuals, 6.3% is attributable to variation between the two breeding areas (93.7% of the variation is within breeding areas). Pairwise F-ST values showed low genetic differentiation (F-ST's <0.012) among breeding colonies within The Netherlands. The level of genetic differentiation indicates that the level of gene flow between The Netherlands and Mauritania is much lower (similar to 4-5 individuals/generation) than among the Dutch colonies on separate Wadden Sea islands. Field observations on individually colour-marked birds from The Netherlands indeed suggest extensive dispersal within northwest Europe, with some introgression of leucorodia genes into the balsaci population. The level of microsatellite distinctiveness between sympatric populations of the two subspecies is similar to that recorded for subspecies of other migrant birds, and as such justifies the subspecies status of the Mauritanian Spoonbill.

Under the ideal-free distribution, omniscient individuals with similar habitat requirements that are free to move should be distributed such that no individual can improve fitness by changing sites; deviations would indicate trade-offs and constraints on ranging behavior. We studied site occupancy and annual survival in red knots Calidris c. canutus at their main wintering area Banc d'Arguin, Mauritania. We collected mark-resighting data at 2 high-tide roosts (A and B) that were only 3 km apart and within sight. Birds were faithful to their roosts and foraged in nearby intertidal areas, with no overlap between birds from A and B. Shellfish-rich seagrass beds were of greater abundance for birds roosting at A than at B. During 8 winters, we found different sex ratios (48% and 58% males at A and B, respectively) and different proportion of juveniles (22% and 45%) at the 2 roosts. Adult annual survival was higher at A (0.830.01 standard error [SE]) than at B (0.810.03). Though rare, between winter season movements were 3 times more frequent from B to A than vice versa, indicating that knots can assess the differences in site quality: birds behaved as if they were ideal. As larger females and older birds occurred more at A, differences in competitive ability might maintain the site occupancy pattern. As females return from the high Arctic breeding grounds first, and adults return before juveniles, priority of occupancy may also play a role. Such an advantage of arriving earlier would represent a seasonal carryover effect.

The reciprocal effects between sediment texture and seagrass density are assumed to play an important role in the dynamics and stability of intertidal-coastal ecosystems. However, this feedback relationship has been difficult to study empirically on an ecosystem scale, so that knowledge is mainly based on theoretical models and small-scale (experimental) studies. In this paper we apply a non-recursive structural equation model (SEM) to empirically investigate, at large spatial scale, the mutual dependence between seagrass (Zostera noltii) density and sediment texture, on the pristine, seagrass-dominated, intertidal mudflats of the Banc d'Arguin, Mauritania. The non-recursive SEM allows consistent estimation and testing of a direct feedback between sediment and seagrass whilst statistically controlling for the effects of nutrients and abiotic stress. The resulting model is consistent with the hypothesized negative feedback: grain size decreases with seagrass density, whereas fine grain size has a negative impact on seagrass density because it decreases pore water exchange which leads to hypoxic sediment conditions. Another finding is that seagrass density increases with sediment organic material content up to a threshold level beyond which it levels off. In combination with decreasing grain size, accumulation of organic matter creates hypoxic sediment conditions which lead to the production of toxic hydrogen sulfide which slows down seagrass growth. The negative feedback loop implies that intertidal Z. noltii modifies its own environment, thus controlling its growing conditions. To the best of our knowledge, this study is the first to demonstrate a direct negative feedback relationship in ecosystems by means of a non-recursive SEM.

The spatial distribution of foraging animals at a given time simultaneously depends on (1) exogenous environmental variables such as resource availability and abiotic habitat characteristics, and (2) the endogenous variable social aggregation made up of the opposing mechanisms of conspecific attraction and repulsion. We developed an exogenous environment-social aggregation model to analyse the spatial distributions of six abundant shorebird species in the Dutch Wadden Sea at resolutions of 150 x 150, 200 x 200 and 250 x 250 m. We used these resolutions to check the robustness of the estimates to the modifiable areal unit problem. We estimated the model parameters by spatial autoregression. This approach enables, among others, estimation of the direct and indirect effects of an exogenous environmental variable on animal density. The former is given by the regression coefficient and the latter, which is due to the amplification of the direct effect by social aggregation, by the spatial multiplier. At all resolution levels and for all species, the explanatory power of social aggregation, measured by Nagelkerke R-2, was larger than the combined contribution of the exogenous environmental variables food availability, silt content and mudflat elevation. Social aggregation was stronger for dunlin, Calidris alpina, red knot, Calidris canutus, and curlew, Numenius arquata, than for oystercatcher, Haematopus ostralegus, grey plover, Pluvialis squatarola, and bar-tailed godwit, Limosa lapponica. The total impacts (that is, direct effect plus all indirect impacts) of the exogenous environmental predictors tended to exceed substantially the direct effects (which tend to be the only ones examined in studies on foraging distributions).

The fuelling performance of long-distance migrants at staging areas indicates local conditions and determines the viability of migration routes. Here we present a first case study where long-term fuelling performance was documented along two migration routes with differential population trends. Ruffs (Philomachus pugnax) are shorebirds of inland freshwater wetlands that migrate from the sub-Saharan wintering grounds, via Europe, to the northern Eurasian breeding grounds. Assessments from 2001 to 2008 of fuelling during northward migration at the major western and eastern staging site revealed that daily mass gain rates steeply declined across years in the grasslands for dairy production in Friesland, The Netherlands, and remained constant in the Pripyat floodplains in Belarus, 1500 km further east. Migrants in Friesland decreased from 2001 to 2010 by 66%, amounting to a loss of 21,000 individuals when counts were adjusted for length of stay as determined by resightings. In the same period numbers in Pripyat increased by 12,000. Ruffs individually ringed in Friesland were resighted in subsequent springs at increasingly eastern sites including Pripyat. Our results corroborate published evidence for an eastward redistribution of Arctic breeding ruffs and suggest that the decreasing fuelling rates in the westernmost staging area contribute to this redistribution. The shift implies that responses occur within a single generation. The hypothesis that the choice of route during northward migration may be driven by food availability can now be tested by creating greater areas of wet grasslands in Friesland. When local staging conditions improve we predict that ruffs will make the reverse shift.

Seagrasses evolved from terrestrial plants into marine foundation species around 100 million years ago. Their ecological success, however, remains a mystery because natural organic matter accumulation within the beds should result in toxic sediment sulfide levels. Using a meta-analysis, a field study, and a laboratory experiment, we reveal how an ancient three-stage symbiosis between seagrass, lucinid bivalves, and their sulfide-oxidizing gill bacteria reduces sulfide stress for seagrasses. We found that the bivalve-sulfide-oxidizer symbiosis reduced sulfide levels and enhanced seagrass production as measured in biomass. In turn, the bivalves and their endosymbionts profit from organic matter accumulation and radial oxygen release from the seagrass roots. These findings elucidate the long-term success of seagrasses in warm waters and offer new prospects for seagrass ecosystem conservation.

The long-distance migrant red knot (Calidris canutus ssp. rufa Scolopacidae) alternates between the northern and southern ends of the New World, one of the longest yearly migrations of any bird and paradoxically overflying apparently suitable habitat at lower latitudes. This subspecies is sharply declining, with a major mortality event following 2000, attributed to commercial overharvesting of food resources at its Delaware Bay (USA) stop-over site. A full understanding of this peculiar migrant requires an assessment of the foraging conditions at its southern hemisphere wintering sites. Here, for a major wintering site in Argentinean Tierra del Fuego (Rio Grande), we describe and compare food abundance, diet and intake rates during JanuaryFebruary in 1995, 2000 and 2008. The two main prey types were the burrowing clam Darina solenoides and three species of epibenthic mussels Mytilidae. In the year 2000, food availability and intake rate were higher than those recorded at other sites used by knots anywhere else in the world, contributing to the explanation of why red knots carry out this impressive migration. Intake rate in 2008 on the two main prey types was dramatically reduced as a result of birds eating smaller prey and strongly increased human disturbance; the same year we also found a high prevalence of a digenean parasite in Darina. We suggest that during the strongly enhanced winter mortality in 2000, knots did not yet face ecological problems in their southernmost wintering area, consistent with the previous evidence that problems at northern stop-overs negatively affected their numbers. However, in 2008 the ecological conditions at Rio Grande were such that they would have facilitated a further decline, emphasizing the importance of a hemispheric approach to research and management.

The development and maintenance of spatial patterns and the way they affect the dynamics of populations and ecosystems is a key issue in ecology. Since each individual and each species experiences the environment on a unique range of scales, it is vital to determine the spatial scales across which organisms interact with each other and the structuring influence of their environments, which can be achieved by analyzing species’ distribution patterns. Here, the spatial variation in the distribution of Scrobicularia plana is described for 4 intertidal areas along the species’ distributional range. Spatial autocorrelation correlograms based on Moran’s coefficient reveal that while the Trondheim (Norway) population was randomly distributed, at Minho (Portugal), the Westerschelde, and the Wadden Sea (both in The Netherlands) populations were aggregated. Patch diameter varied from 150 to 1250 m, in Minho and Westerschelde, respectively; while in the Wadden Sea, patches of 4 to 10 km were detected. Comparisons of spatial patterns with those of other co-occurring bivalve species (Abra tenuis, Cerastoderma edule, and Macoma balthica) revealed that S. plana’s distribution was generally patchier. The distribution of S. plana was correlated with sediment type at Westerschelde and Trondheim, but not Minho. The observed differences in distribution patterns and their correlation with environmental factors reveal that spatial patterns of S. plana are site-specific rather than species-specific.

Patch choice of foraging animals is typically assumed to depend positively on food availability and negatively on interference while benefits of the co-occurrence of conspecifics tend to be ignored. In this paper we integrate a classical functional response model based on resource availability and interference with a conspecific attraction model and use it to simulate spatial distributions of animals in their continuous resource landscapes. We consider both equilibrium and non-equilibrium distributions. We show that the integrated model produces distributions of foraging animals that closely match the distributions observed in nature. The simulations also show that under information uncertainty the locations of flocks are highly variable when conspecific attraction is strong. We furthermore explain how we can estimate the impacts of conspecific attraction and interference on the distribution of foraging animals by spatial autoregression. On the basis of simulated data we show that the separate impacts of interference and conspecific attraction can be disentangled when prior information on either is available, in addition to information on resource density and predator density, and that the total food effect is given by the spatial multiplier.

Two populations of Bar-tailed Godwits Limosa lapponica occur along the East-Atlantic Flyway. The European population (L. I. lapponica) is supposed to breed in northern Scandinavia and has been suggested to only winter in Europe. The Afro-Siberian population (taymyrensis) is supposed to breed in Northern Siberia and is thought to winter exclusively in West Africa. An analysis of 946 metal ring recoveries accumulated by EURING (with data going back to 1935), in combination with an analysis of over 13,000 resightings of almost 4000 individuals marked with colour-rings in 2001-2010, enabled us to examine whether there is evidence for overlap of the populations in summer and winter. Nearly all marked individuals behaved according to the previously suggested leap-frog migration pattern. On the basis of the present sample, only 0.8% of (colour) ringed birds that were recovered and/or resighted on the wintering grounds in Europe or West-Africa made a change between the two supposed wintering areas. This is far less than was previously estimated on the basis of biometric data. The distinct migratory behaviour of the two populations makes them near-completely separated in summer and winter. The Bar-tailed Godwit along the East-Atlantic Flyway thus exhibits a clear leap-frog migration, in which the Siberian breeders winter south of the European breeders.

In 2009 is Emerson Process Management Nederland (EPMN) gestart met de invoering van een nieuwe HR- activiteit, namelijk het op beoordeling en prestatiemanagement gerichte PEP- proces. Aanleiding voor dit nieuwe proces is dat moederorganisatie Emerson de performance van de wereldwijde organisatie wil verbeteren ten voordele van haar concurrentiepositie. Dit nieuwe proces is volgens de ontwerpers van dit proces pas effectief als de lijnmanagers binnen de organisatie met hun medewerkers in gesprek gaan over hun ontwikkeling en functioneren en hun medewerkers hierin ondersteunen. Twee jaar na de invoering van het PEP- proces is bij de directie van EPMN de behoefte ontstaan aan een evaluatie van de werking van dit proces. Onduidelijk is hoe de lijnmanagers zelf aankijken tegen hun rol in dit proces en de mate waarin zij in staat zijn deze rol te vervullen. Dit onderzoek heeft dan ook als doel om na te gaan wat de ervaringen van de lijnmanagers binnen EPMN met het PEP- proces en hun rol in dit proces zijn en welke factoren volgens de lijnmanagers een rol spelen bij de uitvoering van dit proces. Uit dit kwalitatieve onderzoek komt naar voren dat de lijnmanagers binnen EPMN verschillende factoren ervaren die van invloed zijn op hun abilities, motivation en opportunities om het PEP- proces uit te kunnen voeren en dat een aantal van deze factoren een negatieve invloed hierop heeft. Door deze factoren in kaart te brengen is het in dit onderzoek mogelijk EPMN aanbevelingen te doen hoe deze factoren positief te beïnvloeden en daarmee de lijnmanagers binnen EPMN beter in staat te stellen om hun rol in het PEP- proces uit te kunnen voeren. Uit de resultaten blijkt dat de bereidheid en motivatie van de lijnmanagers binnen EPMN om de medewerkers in hun ontwikkeling en functioneren te ondersteunen wordt beïnvloed door de percepties die de lijnmanagers hebben met betrekking tot de rol van de medewerkers in dit proces. In dit onderzoek is door middel van de theorie van het psychologisc

Gek worden ze er soms van, de Waddenzee-liefhebbers die ons horen praten over de wadden van Mauritanië, over de Banc d'Arguin. Over de individuele vogels die we hier in het Waddengebied hebben geringd of gezien, en daar weer hebben teruggevonden. Over de uitgestrekte zeegrasweides en over hoge dichtheden aan wadvogels op dat zeegras. Over de roggen, de haaien, de zeeschildpadden, de reuzenslakken, én over onze overtuiging dat, ondanks de verschillen, er op het Mauretaanse wad lessen verborgen liggen waar we bij het streven naar een rijke zee ons voordeel mee kunnen doen.