The eagle owl (Bubo bubo) is the largest owl in the world with a wingspan of up to 180 cm, a weight of 1.5–3 kg and a length of 60–75 cm. Its great size, stubbornness and ear tufts give it a distinctive appearance. Although it can rest in well-protected and covered areas during the day with little interference, it is on the red list of highly endangered animals in Switzerland.

There are currently around 25 to 35 pairs of eagle owls living in the Swiss canton of Graubünden. There would be room for more than twice as many if only the eagle owl population would grow sufficiently. Eagle owls die too often from non-natural causes. Around 80% of the eagle owls found dead are victims of accidents. RhB’s overhead line masts are also a major risk factor.

Eagle owls are so-called ambush predators, which means that they prefer to watch their prey from above. They keep an eye out for prey such as mice, rats and hares – often from RhB’s overhead line masts. The dangerous thing about these popular observation posts is that the overhead lines are electrically charged. These can short-circuit, especially when birds land and take off, causing the animals to die. This is particularly the case with bird species with large wingspans, such as the eagle owl. In 2018, a third of all eagle owls killed died as a result of a short circuit. In Switzerland, electrocution is the most common, non-natural cause of death of the eagle owl.