“She’s brooding, everything looks fine!” I say to my husband Axel as I focus on the nest through the spotting scope. He makes a quick note of the date and time. It’s April, and we’re busy working on an important mission, dressed in camouflage gear and peering across the Loisach, a river that runs through the Alpine Foreland in Southern Germany. We can see the nest on the opposite bank in one of the crevices of a craggy rock face some 80 meters from where we’re standing. We’re monitoring the nest as part of the eagle-owl species conservation program, a long-term project to protect eagle-owls on the Isar river that was launched by the Bavarian Environment Agency (LfU) and the Bavarian Bird Protection Society (LBV).
Sometimes the whole eagle-owl brood is lost as a result of just one disturbance! If we know where eagle-owls live, then we can protect them.
Even though eagle-owls can reach sizes of up to 67 centimeters, it’s not easy to spot the female crouched in the nest. It’s very important that we don’t disturb the animals, so we need to use high-power optics that are very sensitive to light and that offer excellent levels of magnification. The combination of a Zeiss DiaScope 85 spotting scope and a Vario eyepiece does the job perfectly. With this high-tech equipment, we can make out details of the animal at 75 times magnification, including its delicate ear tufts, luminous orange eyes, and dappled brown plumage.
The female is crouched right down in the nest. These animals hunt as predators, which means they silently fly up to their prey and grab it with their claws from the air, so perfect camouflage is essential.
We also see through our spotting scope that the male has left some food in front of the nest. That’s a good sign! What’s more, the nest cavity looks nice and dry. We only observe the eagle-owls for a few minutes before packing up quietly and slipping away. The priority here is the animals’ welfare, not the excitement of birding!
Germany’s eagle-owl population may have recovered since the 1960s, but it remains fragile, and eagle-owls are still very much in need of protection. At its lowest point, there were no more than 40-odd pairs left. Now this figure has risen to around 2,500, but the danger is far from over. Owls face a long list of hazards, including road and rail traffic, barbed wire, window panes, disturbance of their nests by dog walkers and climbers, forestry work, and a general loss of habitat. Like all birds with a large wingspan, they also face the risk of being electrocuted by poorly insulated power lines.
In fall 2014, we took part in the first group meeting of the “Isar Eagle-owl” species conservation program. One of the most important things we learned was that any efforts to protect eagle-owls have to start with their nesting sites. If an eagle-owl is disturbed while nesting, it may even abandon its brood entirely. That’s why it’s so important to remember that these birds don’t just breed in rocky crags and trees, but also on the forest floor, especially among the roots of spruce trees. People who leave the marked trail can easily frighten away a brooding female, even if they only get within a hundred meters or so, and most people aren’t aware that a single disturbance could lead to the loss of an entire clutch of eggs.
Even if the startled female does eventually return to her nest, it doesn’t take long for the eggs to be destroyed by the cold or eaten by crows.
Our job as volunteers is to start by finding out where the eagle-owls actually live and nest. The next step is to protect their territories and nesting sites, because it’s easy for the relevant authorities to block off walking trails and climbing routes or postpone felling trees to a more appropriate time. Protected nesting sites even affect where you can build new wind turbines, because they have to be a safe distance away.
So how do we even set about finding these well camouflaged, nocturnal owls? Basically by heading out in their mating season and listening for their distinctive hoot, a resonant, two-syllable “ooh-hu” sound. Between January and March the male calls the female in the twilight hours. Armed with that knowledge, the founder and head of the LVB owl group Daniela zum Sande asked us all to help out with a large-scale ‘eavesdropping operation’ along the Isar. We were just two of a total of 60 volunteers who signed up to patrol the riverbanks over the course of several freezing cold, wintry nights. Our job was not only to listen out for individual animals, but also to note the direction of their call, because that provides a clue as to the location of the nesting site.
Eagle-owl expert Günther von Lossow from the ornithological institute run by the Bavarian Environment Agency in Garmisch-Partenkirchen identified a total of 31 suspected eagle-owl territories along the Isar. Volunteers were chosen to monitor each of these areas. Axel and I were assigned to the Wolfratshausen-Schäftlarn section south of Munich. After a year of observation, it became clear that eagle-owls were indeed living in at least nine of the 31 areas, with a chick being reared in three of them.
Unfortunately ‘our’ female ultimately abandoned her brood. When we subsequently visited the empty nest with LVB biologist Dr. Sabine Tappertzhofen, we found a concealed trail immediately behind it, raising the distinct possibility that the nest had been actively disturbed. Although we were obviously disappointed, the good news was that we could protect this breeding site better the following year. We firmly believe that protecting species from extinction goes hand-in-hand with safeguarding our own future.