Every year, 18 million birds crash in Germany as a result of a collision with glass. In the meantime, this has become one of the biggest problems for our bird world, as building with glass has become an increasing trend.
Birds cannot recognize transparent glass and only see the environment behind it, which can be interesting for them. This often leads to unchecked collisions with the glass panes. Since some species fly rather low and others rather high, the height of the pane does not matter.
Glass must be made visible so that birds can perceive it as an obstacle. BUND only advises the use of non-transparent markings.
Translucent glass such as milk, pressed or ornamental glass as well as glass bricks can be used very well if only a certain incidence of light and not the entire view is desired.
Facades can be made visible to birds in many ways, e.g. by sun protection systems (Brise soleil) made of materials such as textiles, foils, metal, wood, perforated tarpaulins or opaque glass.
If reflective or transparent glass is nevertheless to be used, care should be taken to ensure that the markings for full protection are applied to both sides of free-standing glass panes (e.g. passenger shelters).
For private use, fly screens, waterproof glass paints or curtains with cords are an inexpensive alternative.
The “bird friendliness” of the samples is classified by the number of wild birds flying in a flight tunnel to the sample disc instead of the reference disc. BUND recommends the “highly effective” patterns as listed in the following examples:
Dots on the Eifelplatz in Cologne:
Pattern on a noise barrier at a residential complex in Düsseldorf:
Individually designed patterns
You can see bird silhouettes everywhere, but they don’t help against bird strike. Although they are a selective obstacle, they still cannot perceive the rest of the glass. The colour of the silhouettes doesn’t matter either.
They also do not act as predators as desired and do not frighten the birds, so they would avoid the panes. This theory has already been refuted several times. The only effective variant is, if they are stuck with a distance of 10 cm on the whole surface.
Since UV light is not visible to all bird species, UV reflective patterns do not provide sufficient protection. In artificial lighting, in the evening and at night, UV light cannot be reflected and under certain lighting conditions the reflections of the markings are superimposed by the reflections of the panes.
Further detailed information can be found in the BUND brochure “Vogelschlag an Glas“.