Peter de Vries

Ing. Peter de Vries



Droevendaalsesteeg 10
6708 PB Wageningen

+31 (0) 317 47 34 00

The Netherlands


Peter works in the departement of Animal Ecology. He is an allround assistent with his main focus on spatial ecology


Ing. Peter de Vries (1964) graduated from Rijkshogeschool IJselland in Deventer in 1996. In 1997 he started working at the NIOO Centre for Estuarine and Marine Ecology in Yerseke. At this institute he assisted in the study of the settlement of Cerastoderma edule and the role of substrate dynamics on a tidal sandbank in the Westerschelde. In 1999 he started working as an assistant in a study dealing with the response of phytoplankton to changes in the coastal environment. This research was conducted in co-operation with RIKZ (part of Ministry of Water works and Public transportation) and used the mesocosms at Jacobahaven. In 2003, he joined the department of Plant Animal Interactions.

In 2009 a part of the department of Plant Animal Interactions was merged together with the department of Population of Animals into a new department Animal Ecology. Here Peter is responsible for the data from the aquatic part of this group. He is also responsible for the administration of the resightings of Bewick Swan with neckcollars and is a manager of and Movebank for Bewick Swans. Beside this he is the GIS specialist for Animal Ecology.

Work on Great Tits get more important and from 2021 onwards Peter is working during the breedingseason at Westerheide, the research area of the van Oers group. During the breeding season he is catching hundreds of tits and ringing, measure and bleeding them.

Peter is also a member of the OC. And last but not least; he is doing 1000+ important and less important things for the AnE department!

Publications, including not work related articles about birds can be found here:

Personal notes
Editor of Dutch Birding (International journal on Palearctic birds)
Peter is a fond birdwatcher and a fanatic twitcher (NL life list now 465 species, gardenlist 153 species)



Editorial board memberships

Journal of Dutch Birding


Peer-reviewed publicaties

  • Dutchbirding

    Influx of Saharan species to Canary Islands after calima storm in February 2020

    Ricard Gutiérrez, Francisco Javier García Vargas, Juan Antonio Lorenzo, Peter De Vries
    INFLUX OF SAHARAN SPECIES TO THE CANARY ISLANDS AFTER A CALIMA STORM IN FEBRUARY 2020 From 22-24 February 2020, a severe calima storm brought African dust and birds to the Canary Islands, in the strongest known storm of this kind. Besides massive arrivals of transaharian migrants, a live recording effort compiled proven records of eight rare African passerines (59 records of 120 individuals) with Desert Wheatear Oenanthe deserti (85 birds) and Isabelline Wheatear O isabellina (27 birds) the most frequent rarities. A migrant Western Lesser Whitethroat Sylvia curruca and a vagrant Cape Gull Larus dominicanus vetula were seen too. Rare desert passerines were recorded at 60 locations of six islands: Fuerteventura (45 birds) and Gran Canaria (35 birds) held most of them. 113 different observers birdwatched during the calima (of those, only 40 were bird finders). The total numbers of finders and rarities per island was statistically correlated. Best days for vagrant arrivals were the first two after the calima ended. Diversity of birds peaked during the first five days but decreased later. The described amount of North African rare birds recorded appears to be linked to the origin and intensity of the wind besides the species phenology. Their interspecific abundance and occurrence was linked to their mainland African distribution, abundance and behaviour.
  • Ardea

    Timing of avian breeding in an urbanized world

    Maaike de Jong, L. Van den Eertwegh, R. Beskers, Peter De Vries, Kamiel Spoelstra, Marcel E. Visser
    A large part of the world is urbanized, and the process of urbanization is ongoing.
    Species differ in the extent to which they are impacted by urbanization, depending
    on adaption capacity, and on the fitness consequences when adaptation lags
    behind. One prominent effect of urbanization is the dramatic change of the nighttime
    environment: in urban areas nights are no longer dark. Here, we studied the
    impact of urbanization on the timing of breeding, which is a key life-history trait.
    We used six years of data from ten common bird species, breeding in nest boxes
    throughout the Netherlands. We took the intensity of artificial light in the form of
    zenithal sky brightness and light emission, as a proxy for urbanization. We found
    a correlation between light levels and seasonal timing in three of the ten species
    (great tit, blue tit and pied flycatcher), but these relationships differed between
    years. The effect of urbanization on seasonal timing is at best weak in our study
    which was however mainly based on areas with relatively low light levels. There is
    a clear lack of data for breeding birds in more urbanized environments, an ever
    expanding habitat for an increasing number of species worldwide.
  • Integrative and Comparative Biology

    Hampered performance of migratory swans: intra- and inter-seasonal effects of avian influenza virus

    Bethany Hoye, Vincent J. Munster, Naomi Huig, Peter De Vries, Kees Oosterbeek, Wim Tijsen, M.R.J. Klaassen, Ron A. M. Fouchier, J.A. Van Gils
    The extent to which animal migrations shape parasite transmission networks is critically dependent on a migrant’s ability to tolerate infection and migrate successfully. Yet, sub-lethal effects of parasites can be intensified through periods of increased physiological stress. Long-distance migrants may, therefore, be especially susceptible to negative effects of parasitic infection. Although a handful of studies have investigated the short-term, transmission-relevant behaviors of wild birds infected with low-pathogenic avian influenza viruses (LPAIV), the ecological consequences of LPAIV for the hosts themselves remain largely unknown. Here, we assessed the potential effects of naturally-acquired LPAIV infections in Bewick’s swans, a long-distance migratory species that experiences relatively low incidence of LPAIV infection during early winter. We monitored both foraging and movement behavior in the winter of infection, as well as subsequent breeding behavior and inter-annual resighting probability over 3 years. Incorporating data on infection history we hypothesized that any effects would be most apparent in naïve individuals experiencing their first LPAIV infection. Indeed, significant effects of infection were only seen in birds that were infected but lacked antibodies indicative of prior infection. Swans that were infected but had survived a previous infection were indistinguishable from uninfected birds in each of the ecological performance metrics. Despite showing reduced foraging rates, individuals in the naïve-infected category had similar accumulated body stores to re-infected and uninfected individuals prior to departure on spring migration, possibly as a result of having higher scaled mass at the time of infection. And yet individuals in the naïve-infected category were unlikely to be resighted 1 year after infection, with 6 out of 7 individuals that never resighted again compared to 20 out of 63 uninfected individuals and 5 out of 12 individuals in the re-infected category. Collectively, our findings indicate that acute and superficially harmless infection with LPAIV may have indirect effects on individual performance and recruitment in migratory Bewick’s swans. Our results also highlight the potential for infection history to play an important role in shaping ecological constraints throughout the annual cycle.
  • Ecosphere

    Breeding in a den of thieves: pros and cons of nesting close to egg predators.

    Jimmy De Fouw, R. A. Bom, Raymond Klaassen, Gerhard J D M Müskens, Peter De Vries, I.Y. Popov, Y.I. Kokorev, B.S. Ebbinge, Bart A. Nolet
    Breeding success of many Arctic-breeding bird populations varies with lemming cycles due to prey switching behavior of generalist predators. Several bird species breed on islands to escape from generalist predators like Arctic fox Vulpes lagopus, but little is known about how these species interact. We studied brent geese Branta bernicla bernicla that share islands with gulls (Larus spec.) in Taimyr, Siberia (Russia). On one hand, gulls are egg predators, which occasionally steal an egg when incubating geese leave the nest for foraging bouts. On the other hand, gulls import marine resources to the islands, enriching the soil with their guano. We considered three hypotheses regarding clutch size of brent geese after partial nest predation. According to the “predator proximity hypothesis”, clutch size is expected to be smallest close to gulls, because of enhanced predator exposure. Conversely, clutch size is expected to be largest close to gulls, because of the supposedly better feeding conditions close to gulls, which might reduce nest recess times of geese and hence egg predation risk (“guano hypothesis”). Furthermore, gulls may defend their nesting territory, and thus nearby goose nests might benefit from this protection against other gulls (“nest association hypothesis”). We mapped goose and gull nests toward the end of the goose incubation period. In accordance with the latter two hypotheses, goose clutch size decreased with distance to the nearest gull nest in all but the lemming peak year. In the lemming peak year, clutch size was consistently high, indicating that partial nest predation was nearly absent. By mapping food quantity and quality, we found that nitrogen availability was indeed higher closer to gull nests, reflecting guanofication. Unlike predicted by the nest association hypothesis, a predation pressure experiment revealed that egg predation rate decreased with distance to the focal gull nests. We therefore propose that higher food availability close to gulls enables female geese to reduce nest recess time, limiting egg predation by gulls.
  • Eurosurveillance

    Wild bird surveillance in the Netherlands around outbreaks of highly pathogenic avian influenza H5N8 virus in 2014 within the context of global flyways

    J.H. Verhagen, Henk P. van der Jeugd, Bart A. Nolet, R. Slaterus, S.P. Kharitonov, Peter De Vries, O. Vuong, F. Majoor, T. Kuiken, R.A.M Fouchier
    Highly pathogenic avian influenza (HPAI) A(H5N8) viruses that emerged in poultry in east Asia since 2010 spread to Europe and North America by late 2014. Despite detections in migrating birds, the role of free-living wild birds in the global dispersal of H5N8 virus is unclear. Here, wild bird sampling activities in response to the H5N8 virus outbreaks in poultry in the Netherlands are summarised along with a review on ring recoveries. HPAI H5N8 virus was detected exclusively in two samples from ducks of the Eurasian wigeon species, among 4,018 birds sampled within a three months period from mid-November 2014. The H5N8 viruses isolated from wild birds in the Netherlands were genetically closely related to and had the same gene constellation as H5N8 viruses detected elsewhere in Europe, in Asia and in North America, suggesting a common origin. Ring recoveries of migratory duck species from which H5N8 viruses have been isolated overall provide evidence for indirect migratory connections between East Asia and Western Europe and between East Asia and North America. This study is useful for better understanding the role of wild birds in the global epidemiology of H5N8 viruses. The need for sampling large numbers of wild birds for the detection of H5N8 virus and H5N8-virus-specific antibodies in a variety of species globally is highlighted, with specific emphasis in north-eastern Europe, Russia and northern China.
  • Journal of Avian Biology

    The exception to the rule: retreating ice front makes Bewick’s swans Cygnus columbianus bewickii migrate slower in spring than in autumn

    Rascha Nuijten, Andrea Kölzsch, J.A. Van Gils, Bethany Hoye, K.H. Oosterbeek, Peter De Vries, M.R.J. Klaassen, Bart A. Nolet
    In the vast majority of migratory bird species studied so far, spring migration has been found to proceed faster than autumn migration. In spring, selection pressures for rapid migration are purportedly higher, and migratory conditions such as food supply, daylength, and/or wind support may be better than in autumn. In swans, however, spring migration appears to be slower than autumn migration. Based on a comparison of tundra swan Cygnus columbianus tracking data with long-term temperature data from wheather stations, it has previously been suggested that this was due to a capital breeding strategy (gathering resources for breeding during spring migration) and/or to ice cover constraining spring but not autumn migration. Here we directly test the hypothesis that Bewick's swans Cygnus columbianus bewickii follow the ice front in spring, but not in autumn, by comparing three years of GPS tracking data from individual swans with concurrent ice cover data at five important migratory stop-over sites. In general, ice constrained the swans in the middle part of spring migration, but not in the first (no ice cover was present in the first part) nor in the last part. In autumn, the swans migrated far ahead of ice formation, possibly in order to prevent being trapped by an early onset of winter. We conclude that spring migration in swans is slower than autumn migration because spring migration speed is constrained by ice cover. This restriction to spring migration speed may be more common in northerly migrating birds that rely on freshwater resources.
  • Basic and Applied Ecology

    Aquatic plant shows flexible avoidance by escape from tuber predation by swans

    Bert Hidding, M.R.J. Klaassen, Thijs de Boer, Peter De Vries, Bart A. Nolet
    Deeper burial of bulbs and tubers has been suggested as an escape against below-ground herbivory by vertebrates, but experimental evidence is lacking. As deep propagule burial can incur high costs of emergence after dormancy, burial depth may represent a trade-off between sprouting survival and herbivore avoidance. We tested whether burial depth of subterraneous tubers is a flexible trait in fennel pondweed (Potamogeton pectinatus), facing tuber predation by Bewick's swans (Cygnus columbianus bewickii) in shallow lakes in winter. In a four-year experiment involving eight exclosures, winter herbivory by swans and all vertebrate summer herbivory were excluded in a full-factorial design; we hence controlled for aboveground vertebrate herbivory in summer, possibly influencing tuber depth. Tuber depth was measured each September before swan arrival and each March before tuber sprouting. In accordance with our hypothesis, tuber depth in September decreased after excluding Bewick's swans in comparison to control plots. The summer exclosure showed an increase in tuber biomass and the number of shallow tubers, but not a significant effect on the mean burial depth of tuber mass. Our results suggest that a clonal plant like P. pectinatus can tune the tuber burial depth to predation pressure, either by phenotypic plasticity or genotype sorting, hence exhibiting flexible avoidance by escape. We suggest that a flexible propagule burial depth can be an effective herbivore avoidance strategy, which might be more widespread among tuber forming plant species than previously thought.
  • Aquatic Botany

    Reduced tuber banks of fennel pondweed due to summer grazing by waterfowl

    A. Gyimesi, Peter De Vries, Thijs de Boer, Bart A. Nolet
    In this study we investigated the effect of summer bird herbivory on the belowground tuber formation of fennel pondweed (Potamogeton pectinatus L.). Cumulative grazing pressure of four waterfowl species (mute swans, mallards, gadwalls and coots) in the summer was calculated based on timing of grazing and body mass of the grazers. The resulting grazing pressures were significantly negatively correlated with mean autumn tuber biomass in three of the four years of study. Moreover, summer grazing pressures explained more of the variance in tuber densities than water depth, sediment particle size distribution or any interactions of these variables did in the same three years. We propose that herbivory early in the summer has the most substantial impact on the clonal reproduction of macrophytes. Herbivores with a high consumption rate and early congregation for moulting may be the key waterfowl species in diminishing propagule biomass. Hence, they may present pre-emptive, time-staggered competition to consumers of the belowground biomass in autumn, such as migratory swans and diving ducks.
  • Aquatic Botany

    Differences in tolerance of pondweeds and charophytes to vertebrate herbivores in a shallow Baltic estuary

    Bert Hidding, (Liesbeth) E.S. Bakker, F. Keuper, Thijs de Boer, Peter De Vries, Bart A. Nolet
    It has been suggested that herbivorous waterfowl may be important in shaping aquatic plant communities in shallow wetlands. As such, a shift from canopy forming pondweeds to bottom-dwelling charophytes in a formerly turbid pondweed dominated lake has been partly attributed to waterfowl herbivory. Here we study the separate and combined effects of both belowground herbivory in spring by whooper swans and Bewick ‘s swans, and grazing in summer by waterfowl and fish on the community composition in a shallow Baltic estuary during one year. The macrophyte community was dominated by charophytes (mainly Chara aspera) with Potamogeton pectinatus and Najas marina present as subdominants. Other species were rare. Both spring and summer herbivory had no effect on total plant biomass. However, P. pectinatus was more abundant in plots that were closed to spring and summer herbivores. N. marina was more abundant in grazed plots, whereas Chara spp. biomass remained unaffected. Probably belowground propagules of both C. aspera and P. pectinatus were consumed by swans but since C. aspera bulbils were numerous it may have compensated for the losses. P. pectinatus may not have fully recovered from foraging on tubers and aboveground biomass. Our results are in line with other studies in Chara dominated lakes, which found no effect of grazing on summer aboveground Chara biomass, whereas several studies report strong effects of herbivory in lakes dominated by P. pectinatus.
  • Oecologia

    Above- and below-ground vertebrate herbivory may each favour a different subordinate species in an aquatic plant community

    Bert Hidding, Bart A. Nolet, Thijs de Boer, Peter De Vries, M.R.J. Klaassen
    At least two distinct trade-offs are thought to facilitate higher diversity in productive plant communities under herbivory. Higher investment in defence and enhanced colonization potential may both correlate with decreased competitive ability in plants. Herbivory may thus promote coexistence of plant species exhibiting divergent life history strategies. How different seasonally tied herbivore assemblages simultaneously affect plant community composition and diversity is, however, largely unknown. Two contrasting types of herbivory can be distinguished in the aquatic vegetation of the shallow lake Lauwersmeer. In summer, predominantly above-ground tissues are eaten, whereas in winter, waterfowl forage on below-ground plant propagules. In a 4-year exclosure study we experimentally separated above-ground herbivory by waterfowl and large fish in summer from below-ground herbivory by Bewick’s swans in winter. We measured the individual and combined effects of both herbivory periods on the composition of the three-species aquatic plant community. Herbivory effect sizes varied considerably from year to year. In 2 years herbivore exclusion in summer reinforced dominance of Potamogeton pectinatus with a concomitant decrease in Potamogeton pusillus, whereas no strong, unequivocal effect was observed in the other 2 years. Winter exclusion, on the other hand, had a negative effect on Zannichellia palustris, but the effect size differed considerably between years. We suggest that the colonization ability of Z. palustris may have enabled this species to be more abundant after reduction of P. pectinatus tuber densities by swans. Evenness decreased due to herbivore exclusion in summer. We conclude that seasonally tied above- and below-ground herbivory may each stimulate different components of a macrophyte community as they each favoured a different subordinate plant species.
  • Ecology

    Compensatory growth in an aquatic plant mediates exploitative competition between seasonally tied herbivores

    Bert Hidding, Bart A. Nolet, Thijs de Boer, Peter De Vries, M.R.J. Klaassen
    The degree to which vertebrate herbivores exploitatively compete for the same food plant may depend on the level of compensatory plant growth. Such compensation is higher when there is reduced density-dependent competition in plants after herbivore damage. Whether there is relief from competition may largely be determined by the life-history stage of plants under herbivory. Such stage-specific compensation may apply to seasonal herbivory on the clonal aquatic plant sago pondweed (Potamogeton pectinatus L.). It winters in sediments of shallow lakes as tubers that are foraged upon by Bewick's Swans (Cygnus columbianus bewickii Yarrell), whereas aboveground biomass in summer is mostly consumed by ducks, coots, and Mute Swans. Here, tuber predation may be compensated due to diminished negative density dependence in the next growth season. However, we expected lower compensation to summer herbivory by waterfowl and fish as density of aboveground biomass in summer is closely related to photosynthetic carbon fixation. In a factorial exclosure study we simultaneously investigated (1) the effect of summer herbivory on aboveground biomass and autumn tuber biomass and (2) the effect of tuber predation in autumn on aboveground biomass and tuber biomass a year later. Summer herbivory strongly influenced belowground tuber biomass in autumn, limiting food availability to Bewick's Swans. In contrast, tuber predation in autumn by Bewick's Swans had a limited and variable effect on P. pectinatus biomass in the following growth season. Whereas relief from negative density dependence largely eliminates effects of belowground herbivory by swans, aboveground herbivory in summer limits both above- and belowground plant biomass. Hence, there was an asymmetry in exploitative competition, with herbivores in summer reducing food availability for belowground herbivores in autumn, but not the other way around.
  • Journal of Animal Ecology

    Longer guts and higher food quality increase energy intake in migratory swans

    J.A. Van Gils, Jan Beekman, P. Coehoorn, E. Corporaal, T. Dekkers, M.R.J. Klaassen, R. van Kraaij, R. de Leeuw, Peter De Vries
    1. Within the broad field of optimal foraging, it is increasingly acknowledged that animals often face digestive constraints rather than constraints on rates of food collection. This therefore calls for a formalization of how animals could optimize food absorption rates. 2. Here we generate predictions from a simple graphical optimal digestion model for foragers that aim to maximize their (true) metabolizable food intake over total time (i.e. including nonforaging bouts) under a digestive constraint. 3. The model predicts that such foragers should maintain a constant food retention time, even if gut length or food quality changes. For phenotypically flexible foragers, which are able to change the size of their digestive machinery, this means that an increase in gut length should go hand in hand with an increase in gross intake rate. It also means that better quality food should be digested more efficiently. 4. These latter two predictions are tested in a large avian long-distance migrant, the Bewick's swan (Cygnus columbianus bewickii), feeding on grasslands in its Dutch wintering quarters. 5. Throughout winter, free-ranging Bewick's swans, growing a longer gut and experiencing improved food quality, increased their gross intake rate (i.e. bite rate) and showed a higher digestive efficiency. These responses were in accordance with the model and suggest maintenance of a constant food retention time. 6. These changes doubled the birds' absorption rate. Had only food quality changed (and not gut length), then absorption rate would have increased by only 67%; absorption rate would have increased by only 17% had only gut length changed (and not food quality). 7. The prediction that gross intake rate should go up with gut length parallels the mechanism included in some proximate models of foraging that feeding motivation
  • Israel Journal of Ecology and Evolution

    Habitat quality estimated from head-dipping time in trampling swans

    Bart A. Nolet, Thijs de Boer, Peter De Vries
    It would be valuable to be able to infer the habitat quality of underwater-feeding birds and mammals from their diving or head-dipping behavior, especially when underwater sampling is difficult. In air-breathing animals that obtain their food by diving from the water surface to the bottom (or any specific depth), the underwater feeding time is expected to be a function of travel time and gain rate. Hence, for a given travel time, the underwater feeding time should reflect the (initial) quality of the patch where the animals forage. We applied this approach to estimate habitat quality of tundra swans digging for starch-rich belowground propagules of aquatic macrophytes on migratory stopover sites. Swans do not travel underwater but instead trample with their heads above water before dipping their heads, and the optimal dive model was adjusted for this. At an autumn staging site, habitat quality estimated from head-dipping time was not significantly different from locally measured habitat quality, but the uncertainty around the estimated quality was large. Significantly longer head-dipping time was recorded at a spring staging site, despite a shorter trampling time. This long underwater feeding time indicated that the habitat quality was lower, while the short trampling time was explained by more shallow burial of belowground propagules at the spring staging site than at the autumn staging site. Both features were corroborated with biomass data. It should be noted, however, that the precision of the indirect method of habitat assessment varies with habitat quality, being greater for low quality habitat, but probably still not very precise. Further research is needed to confirm the inferred low habitat quality of the spring staging site and to clarify how tundra swans complete their vernal migration.
  • Canadian Journal of Zoology-Revue Canadienne De Zoologie

    Simulated winter browsing may lead to induced susceptibility of willows to beavers in spring

    Annelies Veraart, Bart A. Nolet, F. Rosell, Peter De Vries
    Browsing may lead to an induced resistance or susceptibility of the plant to the herbivore. We tested the effect of winter browsing by Eurasian beavers (Castor fiber L., 1758) on food quality of holme willows (Salix dasyclados Wimm.) in and after the following growth season. Shrubs were pruned in February, and new shoots from these (cut) shrubs were compared with those of untreated (uncut) ones in May and November. The shoots were analysed for dry matter, nitrogen, acid detergent fibre, and total phenolics. In May, the leaves from the cut treatment had a better food quality (more water, more nitrogen, and less phenolics) than those from the uncut one. There was in part also a systemic response, with lower total phenolics in both the cut and untreated parts of pruned shrubs (uncut–cut) than in the uncut shrubs. In November, we did not find significant differences in biochemistry of bark among cut, uncut, or uncut–cut treatments. These results are in accordance with a cafeteria experiment in the field: in May the beavers preferred shoots from the cut treatment, but in November they showed no preference. The results suggest that willows invest in compensatory growth rather than a defence response early in the regrowing phase.
  • Journal of Sea Research

    Spatial pattern of early recruitment of Macoma balthica (L.) and Cerastoderma edule (L.) in relation to sediment dynamics on a highly dynamic intertidal sandflat

    H. Bouma, J.M.C. Duiker, Peter De Vries, Peter M.J. Herman, W.J. Wolff
    To investigate the possible relationship between sediment dynamics and spatial distribution of early bivalve recruits, a correlative held study was carried out on a highly dynamic intertidal sandflat in the Westerschelde estuary, SW Netherlands. On a spatial grid, 43 plots over an area of 700 x 800 m(2), early recruits (300-1000 mum mesh fraction) of the tellinid clam Macoma balthica (L.) and the edible cockle Ceratoderma edule (L.) were sampled during the spatfall period (May-June) in 1997. Data were also collected on bed-level height, sediment dynamics and -composition and abundance of adult benthos. The grid covered a range of -50 to + 140 cm with respect to mean-tide level. In both species, maximum early recruitment was Found at the higher part of this range of intertidal levels. The strong gradient in densities from the lower towards the higher intertidal was significantly negatively correlated with sediment dynamics. No significant correlations of early-recruit densities were found with silt content, or with densities of adult benthos. The relationship between early recruitment and bed-level height differed from that observed in Wadden Sea studies of recruits of similar size, where maximum early recruitment occurred in the lower intertidal. It is suggested that in highly dynamic environments, sediment dynamics may have an important influence on passive resuspension of early recruits and on spatial patterns of early recruitment. Based on field and model data, it is discussed which processes could cause the difference in early recruitment patterns in low and highly dynamic intertidal environments. It is concluded that the presence of low-dynamic areas is essential for the success of early recruitment, and thus for the maintenance of bivalve populations. [KEYWORDS: early recruitment; settlement; resuspension; sediment dynamics; bed-level height Wadden sea; mya-arenaria; tidal flats; habitat selection; bivalve larvae; flume flow; settlement; transport; invertebrates; juveniles]
  • Marine Ecology Progress Series

    Migration of the bivalve Macoma balthica on a highly dynamic tidal flat in the Westerschelde estuary, The Netherlands

    H. Bouma, Peter De Vries, J.M.C. Duiker, Peter M.J. Herman, W.J. Wolff
    Population dynamics of the tellinid clam Macoma balthica (L.) were studied at a highly dynamic intertidal sandflat in the Westerschelde estuary, south-western Netherlands. In order to study temporal development of density and population structure (12 size classes from 0.3 to 20 mm), 3 point sampling stations were sampled fortnightly from March 1992 to March 1998. Within the same period, spatial population dynamics was studied seasonally on a spatial grid (700 x 800 m, 43 plots, distance between the plots 100 m), which covered a range in bedlevel height from-50 to +140 cm relative to mean tide level. Quantitative estimations of early recruitment, growth, and survival plus migration were calculated from the temporal and spatial population data. Early recruitment was highest at the higher tidal levels, where the sediment contained the smallest sand grains. In that same area, the highest disappearance of the juvenile M, balthica, caused by emigration and/or mortality, was observed. In the lower intertidal area, where the sediment contained larger sand grains, the number of recruits in the successive classes increased after Size Class 2 to 3 mm. Based on further analysis of the population data, this increase in the number of recruits is concluded to have been mainly caused by immigration of M. balthica to the lower tidal levels. Since there seemed to be no important immigration into the entire spatial grid population, the migration may have been directed from the higher intertidal levels towards the lower. The strong initial early-recruitment pattern, supposed to be comprised of passive processes, became weaker for the successive size classes after Size Class 2 to 3 mm, which resulted in a spatial distribution of Size Class 7 to 8 mm that was neither related to bedlevel height nor to sand grain size. Therefore, active migration processes are suggested to have been of higher importance than passive migration processes. [KEYWORDS: passive resuspension, active migration, secondary settlement, passive deposition, habitat selectivity]

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