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Note: this is a summary, written in English by the author, of his full report which is in Dutch. His webpage: http://www.instnat.be/broedvogels/


Several European field studies have shown that wind turbines can have a negative impact on bird populations. Birds can collide with the turbines during local and seasonal migration, or they can become disturbed in their breeding, resting or feeding area’s. In Flanders (Belgium) there are plans to build a large number of wind turbines, in order to produce 3 % renewable energy from the total electricity production in 2004 (and 5 % in 2010). For this reason, in May 2000 a project was started to study the impact on birds and to produce an atlas of important bird areas and migration routes in order to build up the necessary policy knowledge. The preliminary study results of the impact on birds are presented in the report (in dutch) “Wind turbines and birds in Flanders (Belgium): Preliminary study results in a European context ” (Everaert et al., 2002).

In the period between May 2000 and December 2001 three wind turbine locations were studied: (a) 23 small to medium sized turbines (200-600 kW) at the ‘East dam’ in the port of Zeebrugge, (b) 5 medium sized turbines (600 kW) at the Pathoekeweg along the ‘Boudewijn canal’ in Brugge, and (c) 3 large wind turbines (1500 kW) in Schelle along the Schelde river (until March 2002 for collision victims).
Weekly searches were done for possible collision victims, and the amount of disturbance was measured for resting, foraging, breeding and migrating birds.

We found that the estimated collision numbers varied from 0 to 125 birds/wind turbine/year. The mean number was 23 (East dam), 12 (Pathoekeweg) and 4 (Schelle) birds/wind turbine/year. At 12 sea-directed wind turbines on the ‘East dam’ in the port of Zeebrugge the mean number was 39 birds/wind turbine/year. These numbers are comparable with some locations in the Netherlands, but higher than other. It is important to know that the mentioned numbers of victims have to be regarded as a strict minimum. More intensive research is necessary to have a better picture of the actual number of small birds that are killed (during seasonal migration daily searches are necessary).

The number of collisions on the three studied locations seems to be highly dependent on the number of passing birds, and in less degree with the size of the wind turbine. Most of the victims were abundant present species as Herring Gull Larus argentatus, Lesser Black-backed Gull Larus fuscus and Black-headed Gull Larus ridibundus, but we also found rarer species as Sparrow hawk Accipiter nisus, Kestrel Falco tinnunculus, Peregrine Falcon Falco peregrinus, Kittiwake Rissa tridactyla, Common Tern Sterna hirundo, Little Tern Sterna albifrons and Stonechat Saxicola torquata. At the East dam in the port of Zeebrugge we estimated that 28 terns collided with the wind turbines.

(imagen omitida)

Peregrine falcon, one of the protected species being killed.

The number of locally migrating birds was measured for a few species, and compared with the number of collisions. We estimated that 1 on 3.700 passing gulls collided with the wind turbines at the East dam in Zeebrugge (collision chance). At rotor height this collision chance was 1 on 2.100 passing gulls. At the larger wind turbines of the Pathoekeweg we found for the Herring Gull a bigger collision chance of 1 on 2.200 (all heights) and 1 on 750 (rotor height). For the Little Tern (at the East dam) we estimated that 1 on 27.000 passing birds collided with the wind turbines (and 1 on 12.000 at rotor height). A much higher collision chance (1 on 3.000 at all heights and 1 on 600 at rotor height) was found by the Common Tern.

In some areas the disturbance-factor can have a greater impact than the collision-factor. Because of the short time period and the lack of data of the period before the turbines were build, it was difficult to measure the actual disturbance on resting, foraging and breeding birds on the three study-sites. The minimum distances to the turbines were approximately the same as in foreign studies. Most resting or foraging waterfowl species held a distance of 150-300 m. Some studies in other countries have shown that birds like geese and waders can have a significant disturbance at larger distances of up to 800 m.

Foreign research has also proved that long wind turbine lines or large wind parks can become important barriers on the migration routes of certain species (like ducks) during the non-breeding season. On the three study-sites in Flanders it wasn’t yet possible to explore this finding, but in the breeding season we performed a confined investigation at the wind turbines of the Pathoekeweg and East-dam. At the Pathoekeweg it was found that for certain species the number of locally migrating birds was less after the installation of the turbines, and that some breeding species like Blue Heron Ardea cinerea flew lower or higher than before.
At the wind turbines of the East-dam in Zeebrugge we saw that most gulls and terns, flying between the breeding colonies and feeding areas at sea, just flew among the wind turbines. Therefore, during the breeding season the wind turbine line was no barrier for these birds. The number of reactions (small changes of flight-direction) by these passing birds was dependent on the size of the bird. This conclusion was also made in a number of other studies in different countries. For the Little Tern we found that 0,37 % of the passing birds (at rotor height) made a small change of direction because of the wind turbines. For the Common Tern, Lesser Black-backed Gull and Herring Gull, a small change of direction was detected by 31, 27 and 38 % of the passing birds at rotor height.

Our preliminary data suggest that important bird-areas and migration-routes have to be avoided to build wind turbines. The negative impact can be significant, but is variable between species and locations. Increasing wind parks furthermore signify an extra environmental pressure alongside the existing disturbance sources. In many cases, local studies are needed to estimate the potential impact on birds.

Joris Everaert
Institute of Nature Conservation
Scientific Institute of the Flemish Community (Regional Government)
Kliniekstraat 25 – 1070 Brussels, Belgium
Tel: 0032-2-558.18.27. E-mail: joris.everaert@instnat.be

Everaert, J., Devos, K. & Kuijken, E., 2002. Wind turbines and birds in Flanders (Belgium): Preliminary study results in a European context. Report Institute of Nature Conservation R.2002.03., Brussels. 76 pp. Dutch, English Summary.

Birds and windfarms - Bird Genocide at windfarm sites

For more articles on birds and windfarms, search: "windfarms"

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>> Autor: Mark Duchamp (21/10/2003)
>> Fuente: Joris Everaert, Institute of Nature ConservationScientific Institute of the Flemish Community (Regional Government)

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