Sjoerd Dirksen

• drs
• Senior (bird) ecologist at Sjoerd Dirksen Ecology

The aim of this report is to provide a full overview of ‘state of art’ monitoring systems and methods that are currently available and/or in development, and can be used as (part of) an integrated monitoring programme to measure collision victims and fluxes of birds and/or bats in offshore wind farms. The review will deal with relevant features of...

Assessing the impacts of avian collisions with wind turbines requires reliable estimates of avian flight intensities and altitudes, to enable accurate estimation of collision rates, avoidance rates and related effects on populations. At sea, obtaining such estimates visually is limited not only by weather conditions but more importantly because a h...

Cormorants (Phalacrocorax carbo sinensis) breeding in the heavily contaminated sedimentation area of the rivers Rhine and Meuse have a severely reduced breeding success as compared to several other Dutch colonies. A detailed analysis of reproductive performance in combination with chemical analysis of eggs and food from colonies in differently cont...

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...

Collision of birds with wind turbines is an important negative effect of wind energy generation. Assessments of the potential numbers of bird collisions are required prior to the construction of wind farms. Collision rate models (CRMs) are used as a tool to estimate numbers of collision victims for wind farm initiatives. In the past couple of decad...

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...

In the Netherlands, wintering Common Scoters usually concentrate north of the eastern Wadden Islands, and to a lesser extent in the southwestern Voordelta. In some years however, concentrations are found at other sites. In 2015/16 large numbers of scoters were recorded off the Dutch coast near Bergen/Camperduin. Numbers were estimated from counts o...

In de afgelopen decennia is veel onderzoek uitgevoerd naar de effecten van windturbines op vogels. De potentiële effecten van windturbines op vleermuizen zijn in Nederland echter nog niet generiek onderzocht. Bij de uitvoering van de Flora- en faunawet (en in mindere mate de Natuurbeschermingswet 1998) en bij m.e.r.-procedures zijn de kennisleemtes...

A standardised assessment of all relevant parameters proved to be possible using the protocols. Found carcasses were very few (two) and the acoustic activity showed a large variance. The explanatory power of landscape parameters from Dutch sites is poor since only five wind farms were studied with rather similar landscape parameters. Fitting and al...

Abstract: In the period 2003-2011 offshore platforms in the North Sea have been successfully used for ornithologi- cal monitoring programs following standardised observation protocols. As most seabird observers have a strong interest in other large marine animals, marine mammal observations were included in these systematic observa- tion protocols...

Op veel plaatsen in Nederland, en daar buiten, worden windturbineparken gebouwd. Voor het krij- gen van meer duurzame energie is dat een positieve ontwikkeling, maar wat zijn de effecten op vleermuizen? In Nederland is daar nog maar erg weinig onderzoek naar gedaan. Het bureau van de Zoogdiervereniging en Bureau Waardenburg gaan hier dit jaar veran...

Each winter ∼ 30% of the Northwest European Bewick's Swan Cygnus columbianus bewickii population feeds in Polder Wieringermeer, the Netherlands, on waste crops left after the harvest. The area has also become important for generating energy as a result of wind farm development. This study analyses pre-and post-construction data on Bewick's Swan dis...

Summary Study aim In this report the results are presented of a study of the effects of the Offshore Wind farm Egmond aan Zee (OWEZ) on flight patterns of birds in the area. Targeted species of interest were local seabirds (such as gulls, divers, gannets, scoters, guillemots and auks), migrating seabirds (such as divers and scoters) and migrating n...

The number of offshore wind farms is increasing rapidly, leading to questions about the environmental impact of such farms. In the Netherlands, an extensive monitoring programme is being executed at the first offshore wind farm (Offshore Windfarm Egmond aan Zee, OWEZ). This letter compiles the short-term (two years) results on a large number of fau...

Collision victims among birds are considered one of the major ecological drawbacks of wind energy. When planning wind farms, onshore or offshore, it is often legally required to assess the species-specific number of bird collisions. We made different types of assessments of collision risks of wind farms over the last 15 years. Especially Environ...

We studied collision rate of birds with modern, large 1.65 MW wind turbines in three wind farms in The Netherlands during three months in autumn and winter. Collision rate, after correction for retrieval and disappearance rate, was 0.08 birds per turbine per day on average (range 0.05–0.19). Collision risk, i.e. the number of victims relative to th...

Plaatsing van windturbines is op land al enkele tientallen jaren gemeengoed. De bouw van offshore windparken is pas in de laatste tien jaar volop begonnen. Het onderzoek aan effecten op vogels is in volle gang. Drie typen effecten van windturbines op vogels zijn vastgesteld: aanvaring (vogelsterfte door botsing met rotor of mast), verstoring (habit...

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...

Abstract in Journal of Ornithology 147 supplement (2006) vol. 5 p. 232.

Baseline study carried out in 2003 and 2004 at Meetpost Noordwijk in the Dutch North Sea off Noordwijk, to assess the effects of the OWEZ wind farm on flight paths, flight altitudes and fluxes of migratory and non-migratory birds. This study was followed by an effect study carried out at the OWEZ wind farm from 2007 to 2010; reported in: Krijgsvel...

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...

De Nederlandse overheid heeft doelstellingen voor toepassing van duurzame energie die vooralsnog vooral moeten worden bereikt door op grote schaal windenergie op te wekken. Nederland heeft ruimtegebrek, dus wordt er voor plaatsing van windturbines (ook) gekeken naar de grote open wateren: IJsselmeer/Markermeer, Waddenzee (Afsluitdijk) en Noordzee....

In commission of the Royal Netherlands Air Force and the City of Eindhoven we registered the number of birds aloft on Eindhoven Airport between August 1998 and July 1999 by visual techniques using binoculars. Observations were conducted during four days each month and lasted the full daylight period. Two methods were used: observations in a fixed v...

In commission of the Royal Netherlands Air Force and the City of Eindhoven we registered the number of birds aloft on Eindhoven Airport between August 1998 and July 1999 by visual techniques using binoculars. Observations were conducted during four days each month and lasted the full daylight period. Two methods were used: observations in a fixed v...

Birds and flight safety is an important topic in planning a possible airport island in the North Sea. This even has been ranked as a go / no go factor in the forthcoming decision making process. For this reason, birds and flight safety has been defined as a distinct topic for research within the ONL framework. Several workshops have been convened i...

A study of flight patterns and altitudes of local waders and diving ducks in wetlands. Bremer Beitrage fuer Naturkunde und Naturschutz Band 4 (1999)

During the non-breeding season, the IIsselmeer area in The Netherlands forms an important staging area for large numbers of diving ducks. The birds feed in the open water at varying distances from the coast and roost either in the lee of dikes or in sheltered waters bordering the lakes IIsselmeer and Markermeer. Most species feed during the day and...

The information on the cormorant diet in the non-breeding period was obtained from the analysis of pellets, collected on roosts. Roosts are mainly occupied from September through March. Analysis of pellets shows a discrepancy between the diets of cormorants in the Lake IJsselmeer area (mainly percids) and those along the rivers (cyprinids), reflect...

A review of six years of monitoring the breeding success of cormorants in one of the most polluted areas of the Netherlands (the Biesbosch) is provided. Reproductive success was low because of contaminants like DDE, PCBs, PCDDs and PCDFs. From 1990, there was a steady increase in breeding success, though there was no improvement in the quality of t...

Chironomid species composition and distribution in relation to exposure were studied on a tidal sandy flat at seven sites (average depth 0-50cm), differing in the duration and frequency of the exposure periods. The chironomid assemblages can be divided into an 'upper eulittoral' one, consisting of Chironomus acutiventris, Ch. balatonicus, Einfeldia...

In eight Dutch or Belgian common tern (Sterna hirundo) colonies, breeding biology and food choice were determined, and 15 second eggs were collected from three-egg clutches for artificial incubation, biochemical analysis and analysis of yolk-sac polyhalogenated hydrocarbon (PHAH) levels. Results from these analyses were combined with biological dat...

In recent years relatively high numbers of Red-crested Pochard have been feeding on stoneworts in Lake Gouwzee (Lake IJsselmeer area, The Netherlands). After a period of absence, stoneworts have recently recolonized several shallow lakes in The Netherlands as a result of improving water quality. The ducks visit the area from July - November, with a...

During the course of spring, Cockles Cerastoderma edule and Mussels Mytilus edulis grow in size, while the condition, as measured by the biomass content of shells of a given size, also increases. Condition temporarily drops when the larger individuals spawn. This study investigates the effects of these seasonal changes on the intake rate and the pr...

Sterna

Ecological investigations revealed differences in breeding success of cormorants (Phalacrocorax carbo) between two colonies in The Netherlands In this study the possible role of organohalogen pollutants was investigated. Thirty-nine cormorant eggs were collected from two colonies with marked differences in contamination Seventeen cormorant eggs wer...

The contaminated Scheldt estuary is a wetland of international importance for waterbirds. In eggs of Common Terns (Sterna hirundo) from the brackish zone, concentrations of Hg, Cr, Cu, Cd, Zn, and PAHs did not exceed no-observed effect levels reported in the literature. Eggshell thickness did not differ from the pre-DDT period. However, concentrati...

In 1991 a breeding colony of 180 pairs of Sterna hirundo was situated near Zeewolde in Flevoland. The terns foraged in a neighbouring, shallow fresh water lake (Lake Wolderwijd). Most important prey were roach Rutilus rutilus, smelt Osmerus eperlanus, perch Perca fluviatilis and ruffe Gymnocephalus cernuus. During winter 1990/91, 75% of fish biomas...

Returning from the breeding grounds, Bewick's swans show a clear preference for sago pondweed tubers. For two lakes in the Netherlands, which may hold up to almost half of the entire flyway population, data on timing of arrival, exploitation patterns, and bird numbers in relation to available food stocks are presented. The swans depleted the tuber...

Numbers, proportion of cygnets, brood size and food choice of a large proportion of the W population of Bewick's swans have been established in the whole Netherlands on a bi-weekly basis throughout the winters 1982-83 and 1983-84. From November to March at least 600 were present, including a peak of nearly 9000 in January (55% of the flyway-populat...

Whimbrels Numenius phaeopus are able to consume 2-3 mg ash-free dry mass per second feeding over the short term, but when the intake rate is that high, they have to pause to allow for digestion. If these digestive pauses are taken into account, the maximum crude intake rate is reduced to 1 mg s-l. This maximum intake rate does not increase during t...

Een artikel met resultaten van vier gebiedsdekkende roofvogeltellingen tijdens de wintermaanden van de complete provincie Groningen, uitgevoerd in december 1979, in februari 1980, in december 1980 en in februari 1981.Naast gegevens over aantallen en sex-ratio worden kaartjes gepresenteerd met daarop de verspreiding van de verschillende soorten roof...

[in Dutch, not yet available in English]. Artikel met resultaten van twee complete tellingen van watervogels in de stad Groningen tijdens de strenge winter van 1978/79. De belangrijkste verblijfplaats voor watervogels was het koelwatercircuit van de Hunzecentrale (met name allerlei grachten en kanalen in de stad). Op 13-14 januari 1979 werden in to...