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Introduction
Currently involved in waterbird research and wetland ecology with a focus on habitat use and migration ecology of Black Tern, Common Tern, Purple Heron, Great Reed warbler and Eurasian Bittern. Experience with (sat) GPS transmitters and light level loggers. Also: habitat restoration studies for marshland birds and waders in wet grasslands, species action plans and impact assessments. Many co-operative studies and capacity building projects on birds in wetlands in West Africa (Benin, Ghana, Sierra Leone, Guinea-Bissau) and Ukraine and Russia.
Additional affiliations
January 2015 - November 2015
independent ecologist
Position
- Senior ecologist
January 1994 - December 2014
Publications
Publications (144)
In dit rapport presenteren we de lange termijntrends voor de periode 1990-2021 van een groot aantal vogelsoorten van vochtige graslanden in de Krimpenerwaard. Ook hebben we op basis van dichtheden de totale populaties vanaf 1990 gereconstrueerd. De top vijf soorten met de grootste afname in 30 jaar tijd zijn veldleeuwerik (93%), graspieper (78%), k...
The Black Tern population has declined substantially over the past decades in West Europe and is stable in Central and Eastern Europe. This decline is mainly caused by a lack of suitable nesting habitat in the west, while eastwards natural habitat is still abundant. However, the trend differences between West and Central Europe might also be caused...
Many Afro-Palearctic songbird migrants have declined, with conservation efforts mainly focused on the restoration of breeding habitat. However, pressures outside the breeding season might play a role. This includes the possibility that local relict populations no longer maintain the original phenotypic variation in migration patterns, with a loss o...
Al vele jaren tellen vogelkundigen nesten van kolonievogels met
behulp van kleine drones met eenvoudige camera’s. Die moeten
laag boven een kolonie vliegen en vrij zicht op de nesten hebben.
Dit werkt niet goed in moerasbossen en struwelen. Professionele
drones die hoger vliegen en van meerdere kanten haarscherpe
foto’s maken, bieden een oplossing....
Dispersal is an important behavioral process that plays a significant role in, among others, speciation, population viability, and individual fitness. Despite progress in avian dispersal research, there are still many knowledge gaps. For example, it is of interest to study how dispersal propensity relates to age- and/or sex-specific patterns. Here,...
Diverse landelijk bedreigde sterns en plevieren broeden uitsluitend op kale
pionierbodems. Die biotoop verdwijnt snel, vooral in zoete stilstaande wateren
met een stabiel peil. Wie zulke bodems wil, ontkomt niet aan het kunstmatig
creëren ervan. Om sterns en plevieren broedgelegenheid te bieden, is
vaak een vorm van ‘tuinieren’ op broedeilanden ver...
Hypopigmentation is characterized by the lack of melanin in part or the whole body. For nocturnal or fossorial reptiles, hypopigmentation may be less disadvantageous, as they are less exposed to visually oriented predators. But chromatic anomalies are challenging to observe in fossorial species, such as worm lizards (Amphisbaenia), because they are...
In the Netherlands, Little Terns breed almost exclusively in the Wadden Sea and the southwestern Dutch Delta, in pioneer habitats with sparse or no vegetation. With the construction of the man-made archipelago Marker Wadden in the freshwater lake Markermeer, inland freshwater habitat became available again for breeding
terns. Since 2017, a year aft...
Marker Wadden is a 1000 ha artificial archipelago developed, since 2017, as a novel ecosystem to restore dynamics in a large Dutch freshwater lake with limited natural dynamics. The newly created habitats should, at flyway level, strengthen populations of threatened bird species that depend on dynamic wetlands. The archipelago includes basins with...
Dispersal is an important behavioural process that plays a significant role in, among others, speciation, population viability, and individual fitness. Despite progress in avian dispersal research, there are still many knowledge gaps. For example, it is of interest to study how movement propensity (i.e., nomadic vs. philopatric) relates to age- and...
Black Terns migrate after breeding to fresh and brackish
wetlands to prepare for migration to West-African wintering
areas. In Northwestern-Europe estuaries with substantial
Smelt Osmerus eperlanus populations are crucial. The area
of lake IJsselmeer with the adjacent western Dutch Wadden
Sea is the most import post-nuptial staging site along the
e...
Capsule: Migration studies of tagged Eurasian Bitterns Botaurus stellaris provide information on the behaviour of this secretive species in relation to weather conditions.
Results: Four individuals remained at the breeding sites in winter and did not migrate in response to cold spells. Two individuals covered distances of 300 and 1600 km between st...
Large-scale fencing prevents grazing by herbivorous waterbirds
and leads to successful restoration of emergent reedbeds
Grazing by herbivorous waterbirds has a strong negative impact on the
development of emergent reed beds in Dutch wetlands, and threatens the
Great Reed Warbler population, which breeds at the outer fringes of reed
beds bordering d...
Since the sixties, the population of Gull-billed Terns in Northwest Europe had declined substantially in numbers and distribution, with only one colony remaining in the German Elbe estuary nowadays. Predator-exclusion fencing led to increased reproduction in this colony. In the Netherlands, Gull-billed Terns bred regularly until around 1958 and the...
https://www.natuurkennis.nl/Uploaded_files/Publicaties/obn-2019-111-lz-eutrofe-moerassen-eindrapport.pdf
Vogeleiland De Kreupel in het IJsselmeer is onder meer aangelegd voor sterns en plevieren. Dankzij intensief beheer broeden visdieven er nog. Maar is dit afdoende?
Marsh bird populations in the Netherlands seem to have recovered recently, except for the Great Reed Warbler. Numbers in the Netherlands have declined from 5000 territories in the fifties to less than 100 today. Deterioration of water reed is currently the most important factor for this decline, caused by overgrazing by Greylag Geese Anser anser. F...
De Nederlandse Aardolie Maatschappij BV (NAM) heeft van het Rijk toestemming om aardgas te winnen uit zes velden in het Waddenzeegebied: Moddergat, Nes, Lauwersoog C, Lauwersoog West, Lauwersoog Oost en Vierhuizen Oost (verder MLV-gasvelden). De winning is gestart in 2007.
De belangrijkste voorwaarde is dat de bodem door de gaswinning niet meer daa...
In many bird species intraspecific variation in migration strategies is related to sex or size. The Eurasian Bittern Botaurus stellaris is a sexually size-dimorphic heron species with a vast breeding and wintering range spanning a range of climates. Ringing data show that Bitterns from northern populations migrate westwards or southwards over thous...
Currently, the deployment of tracking devices is one of the most frequently used approaches to study movement ecology of birds. Recent miniaturization of light‐level geolocators enabled studying small bird species whose migratory patterns were widely unknown. However, geolocators may reduce vital rates in tagged birds and may bias obtained movement...
De Nederlandse Aardolie Maatschappij BV (NAM) heeft van het Rijk toestemming om aardgas te winnen uit de zes velden Moddergat, Nes, Lauwersoog C, Lauwersoog West, Lauwersoog Oost en Vierhuizen Oost in het Waddenzeegebied (verder MLV-gasvelden). De winning is gestart in 2007. De belangrijkste voorwaarde is dat de bodemdaling door de gaswinning binne...
In 1932 the Zuiderzee, the estuary of the river IJssel, was closed by a dam. This changed the brackish dynamic wetland into one of the largest fresh water lakes in Europe, lake IJsselmeer-Markermeer. Previously dynamic sand islands became vegetated and the fish community changed dramatically. Formerly migratory fish populations were replaced by a r...
De Nederlandse Aardolie Maatschappij BV (NAM) heeft van het Rijk toestemming om aardgas te winnen uit de zes velden Moddergat, Nes, Lauwersoog C, Lauwersoog West, Lauwersoog Oost en Vierhuizen Oost in het Waddenzeegebied. De winning is gestart in 2007. De belangrijkste voorwaarde is dat de bodemdaling door de gaswinning binnen de toegestane gebruik...
In 2017 new islands have been created in the Markermeer. The archipelago attracted many pioneer bird species and numbers and breeding success of Common Tern and Pied Avocet have been recorded. The numbers are of international importance and their reproduction was very high. So at this moment the islands contribute substantially to threatened specie...
Het IJsselmeergebied is internationaal belangrijk voor visetende watervogels.
Het leefgebied staat helaas onder druk door de huidige
infrastructuur en menselijk gebruik. De visdief is een goede indicator
voor de kwaliteit van het gebied. Dit rapport geeft een overzicht van
recente trends en het broedsucces van visdieven in het IJsselmeergebied.
Het...
Males bring on average more aquatic prey to the chicks, such as fish and beetle
larvae, while females bring more terrestrial insects (mostly imago diptera). Males are slightly
larger than females with larger bills and therefore probably better specialized
in catching fish. The males need more time to find and transport the prey to the chicks.
As th...
Waddenzee vanaf de locaties Moddergat, Lauwersoog en Vierhuizen Advies Auditcommissie over de resultaten van het monitoringsjaar 2016 7 december 2017 / projectnummer: 3205
De Nederlandse Aardoliemaatschappij BV (NAM) wil een productieboring uitvoeren naar het Ternaard gasveld. Dit gasveld ligt op drie kilometer diepte onder de Waddenzee, bij de ge-meente Dongeradeel. Het geproduceerde gas zal naar de bestaande productielocatie bij Mod-dergat worden getransporteerd via een nog aan te leggen pijpleiding. Om de boring,...
The Eurasian Black Tern, Chlidonias niger niger, nests in marshes continuously distributed across Eurasia, but migration routes, staging sites, and nonbreeding distributions are not well understood. In western Europe some populations have declined substantially over several decades (>90%), thus a more complete understanding of breeding site connect...
Scuba divers reveal secrets of Goldeneyes Bucephala clangula wintering in the Veluwerandmeren.
In the winters of 2008/09, 2010/11, 2012/13 and 2013/14 Goldeneyes were counted and their foraging behaviour was studied at lakes Veluwemeer and Wolderwijd, the Netherlands (together referred to as the Veluwerandmeren). In addition, prey availability wa...
Paper on the decline of the Eurasian Bittern population in Noord-Holland. Simultaneous counts of booming males showed an overestimation of 30% in years without simultaneous counts as males move to other booming locations. But a genuine decline is also clear. The decline is discussed and recommendations for habitat improvement are presented.
In the winters of 2008/09, 2010/11, 2012/13 and 2013/14 Goldeneyes were counted and their foraging behaviour was studied at lakes Veluwemeer and Wolderwijd, the Netherlands (together referred to as the'Veluwerandmeren'). In addition, prey availability was studied at 10 observed Goldeneye foraging locations divided over the two lakes in the winter o...
Purple Herons have a restricted distribution in the lower parts of the Netherlands (Fig. 1). They breed in marshes and although feeding densities are highest in marsh habitat, the largest numbers feed in agricultural grasslands with high densities of ditches. So far foraging ranges and location of foraging sites have been described on the basis of...
Monitoring van aardgaswinning onder de Waddenzee vanaf de locaties Moddergat, Lauwersoog en Vierhuizen Advies van de AuditCommissie over de resultaten vaHet Rijksprojectbesluit Gaswinning onder de Waddenzee vanaf de locaties Moddergat, Lau-wersoog en Vierhuizen (hierna het Rijksprojectbesluit) geeft de Nederlandse Aardolie Maat-schappij BV (NAM) de...
By 2013, six of 27 Black Terns (Chlidonias niger) from four Dutch colonies that had received light level geolocators in 2010-2011 had been recaptured. All six recovered individuals migrated to West Africa, but whereas one individual flew there nonstop, the others made stops of varying length en route. These included flights of 2,000-6,000 km betwee...
Het Rijksprojectbesluit Gaswinning onder de Waddenzee vanaf de locaties Moddergat, Lauwersoog en Vierhuizen (hierna het Rijksprojectbesluit) geeft de Nederlandse Aardolie Maatschappij BV (NAM) de mogelijkheid om onder randvoorwaarden aardgas te produceren in het Waddenzeegebied uit de zes velden Moddergat, Nes, Lauwersoog C, Lauwersoog West, Lauwer...
Purple Herons have a restricted distribution in the lower parts of the Netherlands (Fig. 1). They breed in marshes and although feeding densities are highest in marsh habitat, the largest numbers feed in agricultural grasslands with high densities of ditches. So far foraging ranges and location of foraging sites have been described on the basis of...
Purperreigers broeden in Nederland aan de noordrand van hun verspreidingsgebied. Ze trekken na
de broedtijd in groepen en meestal binnen tien dagen naar Afrika. Op trektelposten worden ze in
de ochtend echter nauwelijks wegtrekkend gezien. Omdat er maar op een enkele locatie in de
avond werd geteld, ontstond het idee dat de reigers zeer lokaal en g...
Arctic Terns Sterna paradisaea have an exceptionally long-distance migration, annually travelling back and forth between the Arctic and the Antarctic. Birds from Greenland, Iceland and the USA were recently found to spend most of the non-breeding period in the Weddell Sea, a small part of the large Antarctic range of Arctic Terns. Based on ring rec...
Het Rijksprojectbesluit Gaswinning onder de Waddenzee vanaf de locaties Moddergat, Lauwersoog
en Vierhuizen (hierna het Rijksprojectbesluit) geeft de Nederlandse Aardolie Maatschappij BV (NAM) de mogelijkheid om onder randvoorwaarden aardgas te produceren in het Waddenzeegebied uit de zes velden Moddergat, Nes, Lauwersoog C, Lauwersoog West, Lauwer...
The Dutch breeding population of the Purple Heron migrates to West Africa during August-September. To date only one migration watchpoint (Ridderkerk, Zuid-Holland) has been known for substantial numbers passing during late afternoon and evening, and this site attracts many birdwatchers in this period. As Purple Herons take off for migration from th...
Birds performing long-distance migration without substantial refuelling en route rely on fat reserves accumulated in the post-breeding, pre-migratory period. In order to fill a knowledge gap in the pre-migratory behaviour of purple herons Ardea purpurea, a species conducting a 3,500–4,000 km migration journey within 5–7 days, 12 adult and four juve...
A review of population size developments since 1949 of the Black Tern in the Natura 2000 wetland Nieuwkoopse Plassen. Habitat, behaviour threats and conservation is described.
Large and heavy birds usually use soaring flight during long-distance migration or make regular stopovers en route for substantial refuelling. Purple Herons are large, long-distance migrants. Because of their size, large herons migrating southwards from Europe to Africa were expected to make one or more stop-overs to refuel. However, data from seve...
Black Terns Chlidonias niger have shown a decrease of well over 90% as a breeding bird in The Netherlands during the twentieth century. Two hypotheses have been put forward for this decline: the disappearance of the floating plant Water Soldier Stratiotes aloides, which used to be the favourite nesting substrate of the terns, and a decrease of avai...
Vorig jaar heeft het (toenmalige) ministerie van LNV een nieuwe richtlijn met betrekking tot de uitvoering van de Flora- en faunawet gepubliceerd. De richtlijn getuigt van de behoefte aan een praktischer interpretatie van de verbodsbepalingen. Deze behoefte lijkt vooral door procedurele problemen ingegeven. Ecologische overwegingen spelen geen rol...
Results of a 3 year study on behaviour and movements of 16 Purple herons with satellite transmitters. It provided information on behaviour in the breeding areas, post breeding behaviour and migratory movements and staging sites in the non-breeding period. Above this, many conservation groups could use the project to highlight their efforts.
The habitat and feeding areas of Purple Herons nesting in the Natura 2000 sites Oostelijke Vechtplassen and Naardrmeer have been identified. About 70% of the feeding habitats of these colonies is outside the Natura 2000 protected areas. Mostly in agricultural grasslands.The herons roost in many small tree stands spread over these grasslands. Conser...
Very little is known about the postnuptial ecology of the Purple Heron. In 2007 and 2008 in total 16 Purple Herons (12 adults) received satellite transmitters. During the breeding season these herons used feeding areas at a distance of 1.5-15 km from the breeding colonies. However, after breeding the adults left the colony sites for a permanent sta...
Nocturnal incubating and brooding behavior of the Black Tern (Chlidonias niger) was studied at two colonies in successive years in The Netherlands. In late evening and early morning, nests were checked regularly for female or male nest attendance until or from complete darkness. During daytime females incubated eggs 60% of the time. At night, males...
The most comprehensive survey to date of the wader population of the coast of Sierra Leone was carried out
during Jan–Feb 2005. A total of 66,292 waders of 25 species were counted and the total wader population was
estimated at 75,000–79,000. With a count of over 42,000, one site, Yawri Bay, accounted for over half the total.
Curlew Sandpiper (24,8...
Since the 1970s, the Dutch Common Tern breeding population has been recovering from a serious decline due to organochloride poisoning. The strictly protected bird reserve on Griend in the Dutch Wadden Sea exemplified this, growing to 3300 breeding pairs in 1994. Yet even in this period breeding success on Griend was low and Common Terns often fed t...
Based on empiric data of breeding success and accurate number trends in The Netherlands, a population model for the black
tern was constructed. This model is based on Leslie matrices. Reproductive parameters from the four most important landscape
types (river landscape, agricultural grasslands, peat marsh and heath land/moors) are used as model inp...
We studied phenology, staging time and refuelling in Broad-billed Sandpipers Limicola falcinellus stopping over during spring migration in the Sivash (Black Sea, Ukraine) in May 1991¿94. In the study area, peak staging numbers of 2000¿2500 individuals occurred in the third week of May. In May 1993, 460 birds were marked with a yellow dye and 126 of...
In spring, large numbers of migrating Broad-billed Sandpipers make a stop-over in the Sivash, a shallow lagoon system in the Crimea, Ukraine, between the Black Sea and the Sea of Azov. Observed fuelling rates are high and, in just a few weeks, the birds can build up sufficient departure mass to reach their breeding grounds in a single non-stop flig...
This paper
presents some adaptations to usual primary moult scores in terns. It is proposed to score old
‘arrested’ moult series separately, to facilitate the analysis of moult in the breeding period
more effectively. To do this in a comparable manner, it is proposed to record moult scores
for active series (after breeding) as A = new first series,...
After a strong decline the size of the population of Black Terns breeding in Germany and the
Netherlands remained stable between 1990 and 2003. The number of breeding pairs in Germany
fluctuated between 832 and 1002 without any apparent trend. The population in 2003 was c.
870 pairs. The breeding range of Black Terns in Germany is restricted to the...
The strong decline of Black Terns breeding in oligotrophic mires is in some areas attributed
to the lack of calcium in the chick period due to absence of fish in acidificated soft waters.
The comparable strong decline in the south of The Netherlands was unclear, as abundant acid
tolerant fish still occur in most bogs. In the Malpie, an area with ac...
The Dutch Black Tern breeding population decline was more than 90% since 1950. This paper
reviews the most important causes for decline in the Netherlands. These are deterioration of
nesting substrate, increased human disturbance and related chick starvation as well as bad
food availability or quality in many Dutch wetlands and agricultural areas....
The Red-crested Pochard is one of very few bird species with an ambiguous status in The Netherlands: it was at the same time on the Dutch Red List (1986, 1994) of characteristic and threatened bird species, and listed in an overview of introduced species. The reasons for doubting its wild origin are statements in some publications about birds in ca...
Hoewel de kwaliteit van het moeras een beperkende factor is, wordt het belangrijkste foerageergebied in Nederland in de huidige situatie gevormd door het veenweidegebied, waaronder een zeer aanzienlijk deel regulier agrarisch gebied. De kwaliteit van het veenweidegebied als foerageergebied is afgenomen, waarbij de volgende factoren als belangrijkst...
The Dutch Black Tern Chlidonias niger population showed a decrease of
more than 90% over the past 50 years. In some landscape types this decline
has continued until recently, but Black Terns in other landscapes have
shown a recovery. These trends correlate with differences in breeding success.
Relatively high breeding success was found in riverine...
Zwarte Sterns zijn het grootste deel van hun leven onderweg
langs de kusten van Afrika. De reis voert langs veel landen en
daarbij komen ze in contact met mensen. Onderzoek naar
Zwarte Sterns in Afrika heeft daarom altijd in het teken gestaan
van de interacties tussen mens en vogel. Vooral de vangst van
sterns voor consumptie door de lokale bevolki...
Ringing studies on Black Terns in The Netherlands. Site tenacity, dispersal and survival. In Dutch.
Black Terms use specific, mainly upwelling areas in Africa during northern winter. During the past few years special studies were set up to investigate possible threats to Black Terns in Africa and special attention was given to interactions between fishermen and terms and to age and sex differences in geographical distribution. A first impression...
Numbers, biometrics and feeding ecology of two marsh tern species, the Black Tern (Chlidonias niger) and White-winged Tern (C. leucopterus) were studied in the Sivash, Ukraine in July – August 1996 and 1998. In 1998 the Sivash region was counted completely and, including the nearby Molochnyi Liman, an estimated 30,000 to 40,000 Black Terns and 50,0...