Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Agricultural pastures challenge the attractiveness of natural saltmarsh for a migratory goose
    Dokter, Adriaan M. ; Fokkema, Wimke ; Ebbinge, Barwolt S. ; Olff, Han ; Jeugd, Henk P. van der; Nolet, Bart A. - \ 2018
    Journal of Applied Ecology 55 (2018)6. - ISSN 0021-8901 - p. 2707 - 2718.
    accelerometer - brent geese - GPS tracking - habitat switching - human–goose conflict - migration - pastures - saltmarsh

    Broad-scale land conversions and fertilizer use have dramatically altered the available staging area for herbivorous long-distance migrants. Instead of natural land, these birds rely increasingly on pastures for migratory fuelling and stopover, often conflicting with farming practices. To predict and manage birds’ future habitat use, the relative advantages and disadvantages of natural (e.g. saltmarsh, intertidal) versus anthropogenic staging sites for foraging need to be understood. We compared the migratory staging of brent geese on saltmarsh and pasture sites in spring. Food quality (nitrogen and fibre content), antagonistic behaviour, and body weight were quantified at nearby sites in simultaneous seasons. Individuals were tracked with high-resolution GPS and accelerometers to compare timing of migration and time budgets during fuelling. On pastures, birds rested more and experienced higher ingestion rates, similar or superior food quality and reduced antagonistic interactions than on saltmarsh. Brent geese using fertilized grasslands advanced their fuelling and migration schedules compared to those using saltmarsh. Pasture birds reached heavy weights earlier, departed sooner, and arrived in the Arctic earlier. Intertidal mudflats were frequently visited by saltmarsh birds during the day, and available food there (algae, some seagrass) was of higher quality than terrestrial resources. Availability of intertidal resources was an important factor balancing the otherwise more favourable conditions on pastures relative to saltmarsh. Synthesis and applications. Disadvantages of longer foraging effort, more antagonistic interactions and delayed fuelling schedules on traditional saltmarshes may cause geese to exchange this traditional niche in favour of pastures, especially in a warming climate that requires advancement of migratory schedules. However, due to its high quality, intertidal forage can complement terrestrial foraging, potentially removing the incentive for habitat switches to pastures. The relatively high quality of green algae and seagrass, and birds’ remarkable preference for these resources when available, provides a key for managers to create landscapes that can sustain this specialist’s intertidal lifestyle. To keep natural habitats attractive to staging geese with the purpose of preventing conflicts with farming practices, management actions should focus on conservation and restoration of saltmarsh and especially intertidal habitat.

    Lack of virological and serological evidence for continued circulation of highly pathogenic avian influenza H5N8 virus in wild birds in the Netherlands, 14 November 2014 to 31 January 2016
    Poen, M.J. ; Verhagen, J.H. ; Manvell, R.J. ; Brown, I. ; Bestebroer, T.M. ; Vliet, S. van der; Vuong, O. ; Scheuer, R.D. ; Jeugd, H.P. van der; Nolet, B.A. ; Kleyheeg, E. ; Müskens, G.J.D.M. ; Majoor, F.A. ; Grund, C. ; Fouchier, Ron A.M. - \ 2016
    Eurosurveillance 21 (2016)38. - ISSN 1025-496X - 11 p.

    In 2014, H5N8 clade 2.3.4.4 highly pathogenic avian influenza (HPAI) viruses of the A/Goose/ Guangdong/1/1996 lineage emerged in poultry and wild birds in Asia, Europe and North America. Here, wild birds were extensively investigated in the Netherlands for HPAI H5N8 virus (real-time polymerase chain reaction targeting the matrix and H5 gene) and antibody detection (haemagglutination inhibition and virus neutralisation assays) before, during and after the first virus detection in Europe in late 2014. Between 21 February 2015 and 31 January 2016, 7,337 bird samples were tested for the virus. One HPAI H5N8 virus-infected Eurasian wigeon (Anas penelope) sampled on 25 February 2015 was detected. Serological assays were performed on 1,443 samples, including 149 collected between 2007 and 2013, 945 between 14 November 2014 and 13 May 2015, and 349 between 1 September and 31 December 2015. Antibodies specific for HPAI H5 clade 2.3.4.4 were absent in wild bird sera obtained before 2014 and present in sera collected during and after the HPAI H5N8 emergence in Europe, with antibody incidence declining after the 2014/15 winter. Our results indicate that the HPAI H5N8 virus has not continued to circulate extensively in wild bird populations since the 2014/15 winter and that independent maintenance of the virus in these populations appears unlikely.

    Predicting Effects of Water Regime Changes on Waterbirds: Insights from Staging Swans
    Nolet, Bart A. ; Gyimesi, Abel ; Krimpen, Roderick R.D. Van; Boer, Fred de; Stillman, Richard A. ; Green, Andy J. - \ 2016
    PLoS ONE 11 (2016)2. - ISSN 1932-6203
    Predicting the environmental impact of a proposed development is notoriously difficult,
    especially when future conditions fall outside the current range of conditions. Individualbased
    approaches have been developed and applied to predict the impact of environmental
    changes on wintering and staging coastal bird populations. How many birds make use of
    staging sites is mostly determined by food availability and accessibility, which in the case of
    many waterbirds in turn is affected by water level. Many water systems are regulated and
    water levels are maintained at target levels, set by management authorities. We used an
    individual-based modelling framework (MORPH) to analyse how different target water levels
    affect the number of migratory Bewick’s swans Cygnus columbianus bewickii staging at
    a shallow freshwater lake (Lauwersmeer, the Netherlands) in autumn. As an emerging property
    of the model, we found strong non-linear responses of swan usage to changes in water
    level, with a sudden drop in peak numbers as well as bird-days with a 0.20 m rise above the
    current target water level. Such strong non-linear responses are probably common and
    should be taken into account in environmental impact assessments
    Locomotion during digestion changes current estimates of seed dispersal kernels by fish
    Leeuwen, C.H.A. van; Beukeboom, R. ; Nolet, B.A. ; Bakker, E.S. ; Pollux, B.J.A. - \ 2016
    Functional Ecology 30 (2016). - ISSN 0269-8463 - p. 215 - 225.
    1.Dispersal of seeds by animals is an important mechanism regulating plant diversity, range expansions and invasions. Many birds, mammals, fish and reptiles regularly ingest, transport and excrete viable seeds (known as endozoochory). 2.The effectiveness of endozoochory is modelled in dispersal kernels: functions that describe seed shadows in the landscape by combining movement of animals with experimentally obtained seed retention times and survival. 3.Currently, dispersal kernels use experimental data from resting animals, yet only moving animals disperse seeds. Although physical activity is known to affect digestive processes, little is known on how and to what extent this may influence current estimates of endozoochory. Activity may either prolong seed retention in the animal's gut (locomotion-priority mode hypothesis) or may not affect seed excretion rate (digestion-priority mode hypothesis), and may affect seed survival and germination positively or negatively. 4.We tested how activity alters dispersal estimates in fish. We compared the seed dispersal potential of two riparian plant species (Carex acuta and Carex riparia) by the common carp (Cyprinus carpio) subjected to three different activity levels: low (basal metabolic rate, BMR), medium (2 × BMR) or high activity (3 × BMR). 5.Physical activity of the fish did not affect the number of intact retrieved seeds over 15 h of activity, but significantly affected seed retrieval patterns over time for both seed species. More active fish started seed excretion about 1 h later and kept excreting seeds at least 2 h longer. Effects of gut passage on germination could only be tested for C. acuta, where it reduced the percentage of germinating seeds by 22%, independent of the activity level. Seeds ingested by the fish germinated on average 3·5 days later than non-ingested control seeds. Seed retention times did not affect the timing of germination. 6.Our results support the locomotion-priority mode hypothesis and show that modelling dispersal kernels using parameters from inactive fish may underestimate potential dispersal distances. Because a trade-off between physical activity and digestive physiology is likely common in animals, it should be taken into account in future modelling of endozoochorous seed dispersal kernels.
    What Can Stable Isotope Analysis of Top Predator Tissues Contribute to Monitoring of Tundra Ecosystems?
    Ehrich, Dorothee ; Ims, Rolf A. ; Yoccoz, Nigel G. ; Lecomte, Nicolas ; Killengreen, Siw T. ; Fuglei, Eva ; Rodnikova, Anna Y. ; Ebbinge, Barwolt S. ; Menyushina, Irina E. ; Nolet, Bart A. ; Pokrovsky, Ivan G. ; Popov, Igor Y. ; Schmidt, Niels M. ; Sokolov, Aleksandr A. ; Sokolova, Natalya A. ; Sokolov, Vasily A. - \ 2015
    Ecosystems 18 (2015)3. - ISSN 1432-9840 - p. 404 - 416.
    arctic tundra - diet - ecological indicator - food web - monitoring - predator - stable isotopes - Vulpes lagopus

    Understanding how climate change and increasing human impacts may exert pressure on ecosystems and threaten biodiversity requires efficient monitoring programs. Indicator species have been proposed as useful tools, and predators and their diet may be particularly suitable. The vast and remote arctic tundra represents a good case study as shifts in ecosystem states are presently occurring, and monitoring is a major challenge. Here we assess what stable isotopes reflecting the diet of the arctic fox, a widespread and highly flexible top predator, can contribute to effective monitoring of the vertebrate prey basis of Arctic tundra. We used data collected over 2–5 years from six sites in the Eurasian Arctic and Greenland. Stable isotope signatures of arctic fox winter fur reflected both spatial and temporal variability in the composition of the vertebrate prey basis. Clear contrasts were apparent in the importance of marine resources, as well as of small rodents and their multiannual density fluctuations. Some important resources could however not be separated because of confounding isotopic signatures. Moreover, except for preferred prey, the proportions of prey in the diet may not necessarily reflect the relative importance of species in the community of available prey. Knowing these limitations, we suggest that the arctic fox diet as inferred from stable isotopes could serve as one of several key targets in ecosystem-based monitoring programs.

    Data from: Locomotion during digestion changes current estimates of seed dispersal kernels by fish
    Leeuwen, C.H.A. van; Beukeboom, R. ; Nolet, B.A. ; Bakker, E.S. ; Pollux, B.J.A. - \ 2015
    Wageningen University & Research
    endozoochory - germination - ichthyochory - metabolic rate - riparian plants - seed retention time - Carex - Carex acuta - Carex riparia - Cyprinus carpio
    Dispersal of seeds by animals is an important mechanism regulating plant diversity, range expansions and invasions. Many birds, mammals, fish, and reptiles regularly ingest, transport and excrete viable seeds (known as endozoochory). The effectiveness of endozoochory is modelled in dispersal kernels: functions that describe seed shadows in the landscape by combining movement of animals with experimentally obtained seed retention times and survival. Currently, dispersal kernels use experimental data from resting animals, yet only moving animals disperse seeds. Although physical activity is known to affect digestive processes, little is known on how and to what extent this may influence current estimates of endozoochory. Activity may either prolong seed retention in the animal's gut (locomotion-priority mode hypothesis) or may not affect seed excretion rate (digestion-priority mode hypothesis), and may affect seed survival and germination positively or negatively. We tested how activity alters dispersal estimates in fish. We compared the seed dispersal potential of two riparian plant species (Carex acuta and C. riparia) by the common carp (Cyprinus carpio) subjected to three different activity levels: low (basal metabolic rate, BMR), medium (2×BMR), or high activity (3×BMR). Physical activity of the fish did not affect the number of intact retrieved seeds over 15 h of activity, but significantly affected seed retrieval patterns over time for both seed species. More active fish started seed excretion about 1 h later and kept excreting seeds at least 2 h longer. Effects of gut passage on germination could only be tested for C. acuta, where it reduced the percentage of germinating seeds by 22%, independent of the activity level. Seeds ingested by the fish germinated on average 3.5 days later than non-ingested control seeds. Seed retention times did not affect the timing of germination. Our results support the locomotion-priority mode hypothesis, and show that modelling dispersal kernels using parameters from inactive fish may underestimate potential dispersal distances. Because a trade-off between physical activity and digestive physiology is likely common in animals, it should be taken into account in future modelling of endozoochorous seed dispersal kernels.
    Experimental evidence for inherent Lévy search behaviour in foraging animals
    Kölzsch, A. ; Alzate, A. ; Bartumeus, F. ; Jager, M. de; Weerman, E.J. ; Hengeveld, G.M. ; Naguib, M. ; Nolet, B.A. ; Koppel, J. van de - \ 2015
    Proceedings of the Royal Society. B: Biological Sciences 282 (2015)1807. - ISSN 0962-8452 - 9 p.
    correlated-random-walks - environmental complexity - wandering albatrosses - movement patterns - marine predator - flight - strategies - success - evolve - scale
    Recently, Lévy walks have been put forward as a new paradigm for animal search and many cases have been made for its presence in nature. However, it remains debated whether Lévy walks are an inherent behavioural strategy or emerge from the animal reacting to its habitat. Here, we demonstrate signatures of Lévy behaviour in the search movement of mud snails (Hydrobia ulvae) based on a novel, direct assessment of movement properties in an experimental set-up using different food distributions. Our experimental data uncovered clusters of small movement steps alternating with long moves independent of food encounter and landscape complexity. Moreover, size distributions of these clusters followed truncated power laws. These two findings are characteristic signatures of mechanisms underlying inherent Lévy-like movement. Thus, our study provides clear experimental evidence that such multi-scale movement is an inherent behaviour rather than resulting from the animal interacting with its environment.
    Deriving animal behaviour from high-frequency GPS: tracking cows in open and forested habitat
    Weerd, N. de; Langevelde, F. van; Oeveren, H. van; Nolet, B.A. ; Kölzsch, A. ; Prins, H.H.T. ; Boer, W.F. de - \ 2015
    PLoS ONE 10 (2015)6. - ISSN 1932-6203 - 17 p.
    collar performance - large herbivores - telemetry data - movement - cattle - ecology - states - technology - selection - position
    The increasing spatiotemporal accuracy of Global Navigation Satellite Systems (GNSS) tracking systems opens the possibility to infer animal behaviour from tracking data.We studied the relationship between high-frequency GNSS data and behaviour, aimed at developing an easily interpretable classification method to infer behaviour from location data. Behavioural observations were carried out during tracking of cows (Bos Taurus) fitted with high-frequency GPS (Global Positioning System) receivers. Data were obtained in an open field and forested area, and movement metrics were calculated for 1 min, 12 s and 2 s intervals. We observed four behaviour types (Foraging, Lying, Standing and Walking). We subsequently used Classification and Regression Trees to classify the simultaneously obtained GPS data as these behaviour types, based on distances and turning angles between fixes. GPS data with a 1 min interval from the open field was classified correctly for more than 70% of the samples. Data from the 12 s and 2 s interval could not be classified successfully, emphasizing that the interval should be long enough for the behaviour to be defined by its characteristic movement metrics. Data obtained in the forested area were classified with a lower accuracy (57%) than the data from the open field, due to a larger positional error of GPS locations and differences in behavioural performance influenced by the habitat type. This demonstrates the importance of understanding the relationship between behaviour and movement metrics, derived from GNSS fixes at different frequencies and in different habitats, in order to successfully infer behaviour. When spatially accurate location data can be obtained, behaviour can be inferred from high-frequency GNSS fixes by calculating simple movement metrics and using easily interpretable decision trees. This allows for the combined study of animal behaviour and habitat use based on location data, and might make it possible to detect deviations in behaviour at the individual level.
    Scatter hoarding and cache pilferage by superior competitors: an experiment with wild boar, Sus scrofa
    Suselbeek, L. ; Adamczyk, V.M.A.P. ; Bongers, F. ; Nolet, B.A. ; Prins, H.H.T. ; Wieren, S.E. van; Jansen, P.A. - \ 2014
    Animal Behaviour 96 (2014). - ISSN 0003-3472 - p. 107 - 115.
    optimal-density model - dipodomys-merriami - kangaroo rats - environmental-conditions - acorn dispersal - red squirrel - wood mice - seed - behavior - rodents
    Food-hoarding patterns range between larder hoarding (a few large caches) and scatter hoarding (many small caches), and are, in essence, the outcome of a hoard size–number trade-off in pilferage risk. Animals that scatter hoard are believed to do so, despite higher costs, to reduce loss of cached food to competitors against which they cannot defend their food reserves (henceforth: superior competitors). We tested the underlying assumption that the cost of having more caches under scatter hoarding, thus increasing the likelihood of cache encounter by superior competitors, is outweighed by the benefit of having small caches that are less likely to be detected upon encounter by superior competitors. We carried out a controlled experiment in which we distributed a fixed number of acorns over a fixed number of patches within a fixed area, varying cache size and cache depth, thus mimicking alternative hoarding patterns. We then recorded cache pilferage by a fixed number of wild boar, a well-known pilferer of acorn caches. The time wild boar needed to pilfer the first cache was shortest for scatter hoarding, but the time needed to pilfer all caches was slightly longer for scatter hoarding than for larder hoarding. Overall, however, the rate of pilferage did not differ between scatter hoarding and larder hoarding, and was not affected by cache depth. We conclude that the effects of alternative hoarding patterns on reducing cache pilferage by wild boar were smaller than expected, and that superior competitors may thus not be important drivers of scatter hoarding. Instead, other factors, such as conspecific pilferage or the risk of cross-contamination of food items in large caches, which can also cause catastrophic loss of food reserves, may be more important drivers of scatter hoarding.
    How superdiffusion gets arrested: ecological encounters explain shift from Lévy to Brownian movement
    Jager, M. de; Bartumeus, F. ; Kölzsch, A. ; Weissing, F.J. ; Hengeveld, G.M. ; Nolet, B.A. ; Herman, P.M.J. ; Koppel, J. van de - \ 2014
    Proceedings of the Royal Society. B: Biological Sciences 281 (2014)1774. - ISSN 0962-8452 - 8 p.
    power-law distributions - flight search patterns - environmental complexity - walks evolve - predators - dynamics - animals - mussels - success
    Ecological theory uses Brownian motion as a default template for describing ecological movement, despite limited mechanistic underpinning. The generality of Brownian motion has recently been challenged by empirical studies that highlight alternative movement patterns of animals, especially when foraging in resource-poor environments. Yet, empirical studies reveal animals moving in a Brownian fashion when resources are abundant. We demonstrate that Einstein's original theory of collision-induced Brownian motion in physics provides a parsimonious, mechanistic explanation for these observations. Here, Brownian motion results from frequent encounters between organisms in dense environments. In density-controlled experiments, movement patterns of mussels shifted from Lévy towards Brownian motion with increasing density. When the analysis was restricted to moves not truncated by encounters, this shift did not occur. Using a theoretical argument, we explain that any movement pattern approximates Brownian motion at high-resource densities, provided that movement is interrupted upon encounters. Hence, the observed shift to Brownian motion does not indicate a density-dependent change in movement strategy but rather results from frequent collisions. Our results emphasize the need for a more mechanistic use of Brownian motion in ecology, highlighting that especially in rich environments, Brownian motion emerges from ecological interactions, rather than being a default movement pattern
    Combining Levy walks with path exploitation rules, and exploration of optimal exploration- exploitation strategies
    Hengeveld, G.M. ; Koelzsch, A. ; Koppel, J. van de; Naguib, M. ; Nolet, B.A. - \ 2013
    Faltering lemming cycles reduce productivity and population size of a migratory Arctic goose species
    Nolet, B.A. ; Bauer, S. ; Feige, N. ; Kokorev, Y. ; Popov, I.Y. ; Ebbinge, B.S. - \ 2013
    Journal of Animal Ecology 82 (2013)4. - ISSN 0021-8790 - p. 804 - 813.
    geese branta-bernicla - nyctea-scandiaca nests - brent geese - clutch size - climate-change - b.-bernicla - reproductive-performance - trophic interactions - incubation behavior - northeastern taimyr
    1. The huge changes in population sizes of Arctic-nesting geese offer a great opportunity to study population limitation in migratory animals. In geese, population limitation seems to have shifted from wintering to summering grounds. There, in the Arctic, climate is rapidly changing, and this may impact reproductive performance, and perhaps population size of geese, both directly (e.g. by changes in snow melt) or indirectly (e.g. by changes in trophic interactions). 2. Dark-bellied brent geese (Branta bernicla bernicla L.) increased 20-fold since the 1950s. Its reproduction fluctuates strongly in concert with the 3-year lemming cycle. An earlier analysis, covering the growth period until 1988, did not find evidence for density dependence, but thereafter the population levelled off and even decreased. The question is whether this is caused by changes in lemming cycles, population density or other factors like carry-over effects. 3. Breeding success was derived from proportions of juveniles. We used an information-theoretical approach to investigate which environmental factors best explained the variation in breeding success over nearly 50 years (1960–2008). We subsequently combined GLM predictions of breeding success with published survival estimates to project the population trajectory since 1991 (year of maximum population size). In this way, we separated the effects of lemming abundance and population density on population development. 4. Breeding success was mainly dependent on lemming abundance, the onset of spring at the breeding grounds, and the population size of brent goose. No evidence was found for carryover effects (i.e. effects of conditions at main spring staging site). Negative density dependence was operating at a population size above c. 200 000 individuals, but the levelling off of the population could be explained by faltering lemming cycles alone. 5. Lemmings have long been known to affect population productivity of Arctic-nesting migratory birds and, more recently, possibly population dynamics of resident bird species, but this is the first evidence for effects of lemming abundance on population size of a migratory bird species. Why lemming cycles are faltering in the last two decades is unclear, but this may be associated with changes in winter climate at Taimyr Peninsula (Siberia). Key-words: bird migration, climate change, dark-bellied brent goose, density dependence, reproductive success
    Boldness affects foraging decisions in barnacle geese: an experimental approach
    Kurvers, R.H.J.M. ; Nolet, B.A. ; Prins, H.H.T. ; Ydenberg, R.C. ; Oers, K. van - \ 2012
    Behavioral Ecology 23 (2012)6. - ISSN 1045-2249 - p. 1155 - 1161.
    social-context - body-size - herbivorous anatidae - branta-leucopsis - anser-indicus - zebra finches - goose flocks - personality - leadership - behavior
    Individuals foraging in groups constantly need to make decisions, such as when to leave a group, when to join a group, and when to move collectively to another feeding site. In recent years, it has become evident that personality may affect these foraging decisions, but studies where individuals are experimentally forced into different roles are still absent. Here, we forced individual barnacle geese, Branta leucopsis, differing in boldness scores, either in a joining or in a leaving role in a feeding context. We placed a food patch at the far end of a test arena and measured the arrival latency and number of visits of individuals to the patch either in the presence of a companion that was confined near the food patch (“joining context”) or in the presence of a companion that was confined away from the food patch (“leaving context”). We also ran trials without a companion (“nonsocial context”). Bolder individuals arrived more quickly than shyer individuals in the “leaving” context, but there was no effect of boldness in the “joining” context, suggesting that boldness differences are important in explaining variation in leaving behavior but not in joining behavior. The difference in arrival latency between the “joining” and non-social context increased with decreasing boldness score, suggesting that shyer individuals are more responsive to the presence of other individuals (i.e., social facilitation). These results indicate that individual differences in boldness play a role in patch choice decisions of group-living animals, such as when to leave a flock and when to join others at a patch.
    Mallards Feed Longer to Maintain Intake Rate under Competition on a Natural Food Distribution
    Dijk, J.G.B. van; Duijns, S. ; Gyimesi, A. ; Boer, W.F. de; Nolet, B.A. - \ 2012
    Ethology 118 (2012)2. - ISSN 0179-1613 - p. 169 - 177.
    mannikins lonchura-punctulata - interference competition - group-size - public information - foraging success - patch assessment - spatial-pattern - dominance - vigilance - flocking
    Animals foraging in groups may benefit from a faster detection of food and predators, but competition by conspecifics may reduce intake rate. Competition may also alter the foraging behaviour of individuals, which can be influenced by dominance status and the way food is distributed over the environment. Many studies measuring the effects of competition and dominance status have been conducted on a uniform or highly clumped food distribution, while in reality prey distributions are often in-between these two extremes. The few studies that used a more natural food distribution only detected subtle effects of interference and dominance. We therefore conducted an experiment on a natural food distribution with focal mallards Anas platyrhynchos foraging alone and in a group of three, having a dominant, intermediate or subordinate dominance status. In this way, the foraging behaviour of the same individual in different treatments could be compared, and the effect of dominance was tested independently of individual identity. The experiment was balanced using a 4×4 Latin square design, with four focal and six non-focal birds. Individuals in a group achieved a similar intake rate (i.e. number of consumed seeds divided by trial length) as when foraging alone, because of an increase in the proportion of time feeding (albeit not significant for subordinate birds). Patch residence time and the number of different patches visited did not differ when birds were foraging alone or in a group. Besides some agonistic interactions, no differences in foraging behaviour between dominant, intermediate and subordinate birds were measured in group trials. Possibly group-foraging birds increased their feeding time because there was less need for vigilance or because they increased foraging intensity to compensate for competition. This study underlines that a higher competitor density does not necessarily lead to a lower intake rate, irrespective of dominance status.
    Individually tracked geese follow the green wave during spring migration
    Wijk, R.E. van; Kölzsch, A. ; Kruckenberg, H. ; Ebbinge, B.S. ; Müskens, G.J.D.M. ; Nolet, B.A. - \ 2012
    Oikos 121 (2012)5. - ISSN 0030-1299 - p. 655 - 664.
    goose branta-leucopsis - vegetation index - greylag geese - green-wave - climate - phenology - onset - ecology - birds - patch
    Many migratory herbivores seem to follow the flush of plant growth during migration in order to acquire the most nutrient-rich plants. This has also been hypothesized for arctic-breeding geese, but so far no test of this so-called green wave hypothesis has been performed at the individual level. During four years, a total of 30 greater white-fronted geese Anser albifrons albifrons was tracked using GPS transmitters, of which 13 yielded complete spring migration tracks. From those birds we defined stopover sites and related the date of arrival at each of these stopovers to temperature sum (growing degree days, GDD), snow cover, accumulated photoperiod and latitude. We found that geese arrived at spring stopovers close to the peak in GDD jerk; the ‘jerk’ is the third derivative, or the rate of change in acceleration, and GDD jerk maxima therefore represent the highest acceleration of daily temperature per site. Day of snow melt also correlated well with the observed arrival of the geese. Factors not closely related to onset of spring, i.e. accumulated photoperiod and latitude, yielded poorer fits. A comparison with published data revealed that the GDD jerk occurs 1–2 weeks earlier than the onset of spring derived from NDVI, and probably represents the very start of spring growth. Our data therefore suggest that white-fronted geese track the front of the green wave in spring
    A large-scale multi-species spatial depletion model for overwintering waterfowl
    Baveco, J.M. ; Kuipers, H. ; Nolet, B.A. - \ 2011
    Ecological Modelling 222 (2011)20-22. - ISSN 0304-3800 - p. 3773 - 3784.
    white-fronted geese - wigeon anas-penelope - goose anser-brachyrhynchus - functional-response - barnacle geese - sward height - brent geese - carrying-capacity - forage quality - body reserves
    In this paper, we develop a model to evaluate the capacity of accommodation areas for overwintering waterfowl, at a large spatial scale. Each day geese are distributed over roosting sites. Based on the energy minimization principle, the birds daily decide which surrounding fields to exploit within the reserve boundaries. Energy expenditure depends on distance to the roost and weather conditions. Food intake rate is determined by functional responses, and declines with consumption. A shortage occurs when birds cannot fulfil their daily energy requirement. Most foraging takes place on pasture, with complementary feeding for some of the species on cereals and harvest remains. We applied the model to five waterfowl species overwintering in the Netherlands. From a comparison with field data, the model appears to produce realistic grazing pressures on pasture, especially for geese, and a realistic decline in sward height, but the use of arable fields is less in agreement with observations. For current goose and wigeon numbers, hardly any shortages are expected, but extrapolating the population increase observed during the last decade, considerable shortages are expected in the near future (2015). However, we find that several uncertainties may contribute to more severe shortages: a probabilistic (and therefore less optimal) choice of foraging location, a shorter maximum distance to the roost, and a lower effective availability of resources due to disturbances and other edge effects. Between species we find both competition and facilitation. Both type of interactions, as well as the spatial pattern of resource exploitation, are explained from functional responses and energetic costs of the species. --------------------------------------------------------------------------------
    Personality predicts the use of social information
    Kurvers, R.H.J.M. ; Oers, K. van; Nolet, B.A. ; Jonker, R.M. ; Wieren, S.E. van; Prins, H.H.T. ; Ydenberg, R.C. - \ 2010
    Ecology Letters 13 (2010)7. - ISSN 1461-023X - p. 829 - 837.
    public information - great tits - individual-differences - barnacle geese - 3-spined sticklebacks - animal personalities - exploratory-behavior - scrounging behavior - avian personalities - zebra finches
    The use of social information is known to affect various important aspects of an individual's ecology, such as foraging, dispersal and space use and is generally assumed to be entirely flexible and context dependent. However, the potential link between personality differences and social information use has received little attention. In this study, we studied whether use of social information was related to personality, using barnacle geese, Branta leucopsis, where boldness is a personality trait known to be consistent over time. We found that the use of social information decreased with increasing boldness score of the individuals. Individuals had lower feeding times when they did not follow the social information and this effect was unrelated to boldness score. When manipulating social information, thereby making it incorrect, individuals irrespective of their boldness score, learned that it was incorrect and ignored it. Our results show that social information use depends on the personality type of an individual, which calls for incorporation of these personality-related differences in studies of spatial distribution of animals in which social information use plays a role
    The effect of personality on social foraging: shy barnacle geese scrounge more
    Kurvers, R.H.J.M. ; Prins, H.H.T. ; Wieren, S.E. van; Oers, K. van; Nolet, B.A. ; Ydenberg, R.C. - \ 2010
    Proceedings of the Royal Society. B: Biological Sciences 277 (2010)1681. - ISSN 0962-8452 - p. 601 - 608.
    sticklebacks gasterosteus-aculeatus - zebra finches - animal personalities - great tits - individual-differences - fitness consequences - behavioral syndromes - avian personalities - energy reserves - dominance
    Animals foraging in groups can either search for food themselves (producing) or search for the food discoveries of other individuals (scrounging). Tactic use in producer–scrounger games is partly flexible but individuals tend to show consistency in tactic use under different conditions suggesting that personality might play a role in tactic use in producer–scrounger games. Here we studied the use of producing and scrounging tactics by bold and shy barnacle geese (Branta leucopsis), where boldness is a personality trait known to be repeatable over time in this species. We defined individuals as bold, shy or intermediate based on two novel object tests. We scored the frequency of finding food patches (the outcome of investing in producing) and joining patches (the outcome of investing in scrounging) by bold and shy individuals and their feeding time. Shy individuals had a higher frequency of joining than bold individuals, demonstrating for the first time that personality is associated with tactic use in a producer–scrounger game. Bold individuals tended to spend more time feeding than shy individuals. Our results highlight the importance of including individual behavioural variation in models of producer–scrounger games
    Evaluatie Opvangbeleid 2005-2008 overwinterende ganzen en smienten. Deelrapport 6. Foerageergebieden rond Natura2000-gebieden met ganzendoelstellingen
    Knecht, E. ; Kiers, M.A. ; Nolet, B.A. - \ 2009
    Wageningen : Alterra (Alterra-rapport 1843) - 32
    ganzen - overwintering - wildbeheer - voedingsgedrag - draagkracht - nederland - natura 2000 - geese - overwintering - wildlife management - feeding behaviour - carrying capacity - netherlands - natura 2000
    Dit onderzoek evalueert de effectiviteit van de aanwijzing van foerageergebieden in en rond Natura 2000 gebieden. De beschikbare draagkracht van de foerageergebieden in Natura 2000 gebieden en binnen een afstand van 5, 10 en 15 km is vergeleken met de vereiste draagkracht van deze gebieden. De vergelijking laat zien dat de ganzen op regionaal niveau in staat moeten zijn voldoende foerageer- en rustgebied te vinden binnen de regio. Er is dus in theorie voldoende foerageergebied aanwezig. Dat blijkt uit onderzoek van Alterra, in samenwerking met NIOO
    Evaluatie Opvangbeleid 2005-2008 voor overwinterende ganzen en smienten. Deelrapport 1. Een modelberekening van de capaciteit van opvanggebieden voor overwinterende ganzen en smienten
    Nolet, B.A. ; Baveco, J.M. ; Kuipers, H. - \ 2009
    Wageningen : Alterra (Alterra-rapport 1840) - 70
    ganzen - eenden - overwintering - draagkracht - voedingsgedrag - modellen - wildbeheer - nederland - geese - ducks - overwintering - carrying capacity - feeding behaviour - models - wildlife management - netherlands
    Deze modelstudie onderzoekt of de capaciteit van opvanggebieden voldoende is om de aantallen in Nederland overwinterende ganzen (vier soorten) en smienten te herbergen. Het model maakt gebruik van waargenomen aantallen per maand per provincie. Deze worden over de bekende slaapplaatsen verdeeld. In het model streven de vogels naar een energiebalans tegen zo laag mogelijke energetische kosten. De vogels vliegen dagelijks vanaf de slaapplaatsen naar de voor hen beste foerageerterreinen en putten geleidelijk het voedsel uit door er te foerageren. Daarnaast is er een afname van het voedsel door andere oorzaken dan ganzen- en/of smientenvraat. Een tekort treedt op als de vogels niet binnen de opvanggebieden in hun energiebehoefte kunnen voorzien. Het model voorspelt een realistische graasdruk en afname van grashoogte. De modeluitkomsten suggereren dat er bij de huidige aantallen slechts geringe tekorten (
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