Windturbines en vogels in Vlaanderen: voorlopige onderzoeksresultaten en buitenlandse bevindingen

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, between May 2000 and December 2001 a project was performed 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 results of this preliminary study are presented in this report. In the period between May 2000 and December 2001 three wind turbine locations were studied: (1) 23 small to medium sized turbines (200-600 kW) at the ‘East dam’ in the port of Zeebrugge, (2) 5 medium sized turbines (600 kW) at the ‘Boudewijn canal’ in Brugge, and (3) 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. In addition, the number of locally migrating birds was measured for a few species, and compared with the estimated number of collisions. We found that the estimated collision numbers varied from 0 to 125 dead birds/wind turbine/year. The mean number of estimated collisions for the 3 different locations varied from 4 to 23 dead birds/wind turbine/year. The mean numbers are comparable with some locations in the Netherlands, but higher than other. Most of the victims were abundant present species as Herring Gull, Lesser Black-backed Gull and Black-headed Gull, but we also found rarer species as Peregrine Falcon, Kestrel, Sparrowhawk, Little Tern, Common Tern, Kittiwake and Stonechat. 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). On one location it was possible to perform a confined investigation before the turbines were build. It was found that for certain species the number of locally migrating birds was less after the installation of the turbines. The reactions of flying birds varied between species. In many cases large species also showed the largest amount of reactions during flight. This conclusion was also found in a number of other studies in different countries. 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. The minimum distances to the turbines were approximately the same as for other foreign studies. Most resting or foraging waterfowl species held a distance of 150-300 m. Studies in other countries have shown that some birds like geese and waders can have a significant disturbance at larger distances of up to 800 m. Our preliminary data suggest that important bird-areas and migration-routes have to be avoided to build wind turbines. The impact is variable between species and locations. In many cases, local studies are needed to estimate the potential impact on birds.