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Vogels en het Offshore Windpark Egmond aan Zee (OWEZ)
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Birds and Offshore Wind Farm Egmond aan Zee (OWEZ)

NoordzeeWind, an consortium of NUON and Shell, commisioned us to investigate the effects of the Offshore Wind Farm at Egmond aan Zee (OWEZ) on birds. The final report includes various modules of the four years of research. Follow the links for more details on the various research modules, reports and offshore wind farm.


Bird activity in and around the wind farm was measured through a combination of visual observations and automatic radars (Merlin). This provided information on flight activity 24 hours per day and 365 days per year, including at night.

Which species fly in the wind farm?

Gulls formed the vast majority of flight activity in the wind farm. Cormorants used the turbines bases and meteorological mast for perching. Further, seabirds, such as gannet, guillemots and seaducks were recorded as well as migrating land birds including thrushes, warblers, herons and raptors.

Numbers and flight heights of birds

The total numbers of birds that flew through of over the wind farm varied greatly. Numbers peaked during spring and autumn migration. In these periods most birds flew at dusk, dawn or in the night, and at great heights above the turbines. Fewer birds were recorded during summer and winter. In these seasons most movements were of gulls, mostly during the day and at lower altitudes; largely at turbine height.

Complimentary research carried out by IMARES revealed that the wind farm is favourably situated in an area with few birds. The reports from this research can be found on the website of reports and data of NoordzeeWind.


The radar data on flying birds has enabled us to determine the percentages of birds avoiding the entire wind farm (macro-avoidance) and individual turbines (micro-avoidance). This information can be used to determine the potential effects of planned wind farms. In general, seabirds and migrating geese show most avoidance, while gulls and cormorants enter the wind farm more readily (see diagram).

Collision risks at sea

Based on data collected at the offshore wind farm it is possible to estimate the number of birds that collide with the wind turbines. The collision rate doesn't appear to be higher than on land but actually lower. The registration of collision victims at sea is needed to confirm this estimate.

The effect of an offshore wind farm largely depends on its location, the bird community at that location and its size. Our research revealed that the effects of OWEZ on birds is kept minimal due to its location, small size and large spaces between turbines. 

Read more about this research or contact us.

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