Birds | Several million birds may die every year from hitting a window

Roughly several million birds die in Finland every year due to crashing into windows, says BirdLife Finland’s conservation expert and bird atlas coordinator Aapo Salmela.

In Finland, there has been little research into how many birds die due to crashing into windows, so the estimate is indicative. Migratory birds are especially prone to collisions, but all kinds of birds crash into windows. According to Salmela, birds that live permanently in the vicinity of buildings learn to better perceive the windows in their surroundings and thus also avoid them.

“Younger birds are also more likely to crash into windows than older birds, because they are not yet as skilled at flying,” Salmela describes.

SEY Finland’s animal protection expert Sonja Blom estimates that the number of birds crashing into windows has increased even more, since larger windows are popular in many new buildings. According to Blom, windows that are the size of the entire wall and corners where the window continues on both sides are a particularly big risk for birds. Birds may think that they can fly through such a corner.

Blom believes that most collisions occur in green areas where trees are reflected from the window, as it is difficult for birds to distinguish the reflection from the real landscape.

“However, birds crash into the windows of all kinds of areas and buildings – whether it’s a large glass building in the center or a very ordinary apartment building or a single-family house.”

Birds collisions with windows can be prevented by reducing the transparency and reflectivity of the window, advises Aapo Salmela.

“All kinds of curtains and blinds are helpful, and one tip is also that you should leave the windows unwashed. When there is more dirt on the windows, the birds can see them better.”

According to Salmela, there are windows and window films and tapes on the market today that can prevent birds from crashing into windows. One option is, for example, UV patterning, which the human eye cannot distinguish, but which birds can see. Salmela points out that it is easiest and cheapest to take this into account already in the planning phase of a new building by trimming the window surface and transparent window corners.

Sonja Blom says that at the beginning of the year, the city of Helsinki published the Bird-safe construction guide, which contains more tips.

“If the building already exists, you can also try to prevent birds from crashing into the windows, for example with hawk window stickers or by placing something light and mobile in front of the window as a visual barrier, so the bird will not necessarily choose this flight path. Experiences about the functionality of the stickers are, however, conflicting,” says Blom.

Blom reminds that every Finn has a legal obligation to help wild animals, which means that in the event of a collision, one should monitor the situation and act as required. If the bird survives the collision alive, but does not soon fly to its own path or is visibly injured, you should contact, for example, the wildlife manager of SEY Finland’s animal protection.

“It is also important to remember that a bird that appears to be dead must not be buried until its body has stiffened, as birds that have often crashed into windows can appear to be dead before they come alive.”

It is also common for birds to crash, hunch over, wake up and take off, but later die from their injuries.

The windows are not the only danger that threatens birds in Finns’ yards. The most significant threat is pets roaming freely outside, especially cats. For example, according to a 2015 study by the University of Turku, cats kill around 1.8 million birds in Finland every year, says Salmela.

“This estimate is on the low side, because the study was based on how many of the birds the cats have killed bring home for display, but they don’t bring all of them, they also kill them elsewhere. Cats should not be released into the wild. It is also important from the point of view of the cats’ own safety,” says Salmela.

Salmela reminds that felling trees and clearing bushes should be done outside the birds’ nesting season, because during the nesting season the activity will very likely disturb the nesting and destroy the nests. The birds’ breeding season is from the beginning of April to the end of July.

Many people, for example, protect their berry bushes from birds with various means. Blom points out that plastic nets and fences in particular are dangerous for birds, as birds are easily caught in them.

“From the point of view of all natural animals, it would be good to keep the yard as natural as possible,” says Blom.