Window collisions do not happen very frequently. There are more serious threats to birds, such as wind turbines, that should be dealt with first.
Facts
In North America alone, one billion birds die every year crashing into glass, compared to fewer than one million crashing into wind turbines.1
While the Netherlands has many wind turbines, and the number keeps rising, the number of windows is far greater and rising ever faster.
In short: Glass is one of the leading human causes of bird death.
Very little research on window collisions has been done in Europe, but in Germany the estimated death toll is 100 to 150 million birds per year2. There’s no reason to think the problem is any less serious in the Netherlands.
According to one scientific study from 20143, every structure with glass kills between 2 and 9,4 birds every year. Do the math.

- Loss, Scott R., Tom Will, Sara S. Loss and Peter P. Marra. 2014. Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability. Condor 116:8-23. https://doi.org/10.1650/CONDOR-13-090.1 ↩︎
- Länderarbeitsgemeinschaft der Vogelschutzwarten (LAGVSW). 2017. Der mögliche Umfang von Vogelschlag an Glasflächen in Deutschland – eine Hochrechnung Länderarbeitsgemeinschaft der Vogelschutzwarten. [The possible dimension of bird collision with glass in Germany – an extrapolation by the state working group of bird sanctuaries.] Berichte zum Vogelschutz 53/54: 63–67. ↩︎
- Loss, Scott R., Tom Will, Sara S. Loss and Peter P. Marra. 2014. Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability. Condor 116:8-23. https://doi.org/10.1650/CONDOR-13-090.1 ↩︎