Ducks living in cities often breed in flower pots on balconies and roof terraces, as these offer a sheltered spot.
The challenge lies in safely transporting their young to a nearby lake or river after they hatch.
"You might have a duck who breeds on the 16th floor of a tower block in Spandau. But how to get to the water afterwards with the chicks - unfortunately it doesn't think that far ahead," says Marc Engler, head of the NABU Berlin wild bird centre.
Engler and his colleagues have been helping mallard ducks move for several years, because once the chicks have hatched, the journey to the water can be life-threatening.
Not only do ducks and young animals often have to overcome major differences in altitude, but they also have to survive road traffic.
They provide a very rare form of relocation support. Nationwide, Engler says he only knows of one similar project, in Leipzig.
So breeding season is a busy time for he and his colleagues in Berlin. "We get several calls a day from concerned citizens asking for help," says Engler.
He describes a recent call, with one from a family based in a new housing estate in Berlin's Adlershof district.
Engler his colleague Marco Stelter set out to help, equipped with a cloth bag, a transport box and food, which they use to distract the duck while they are trying to catch it.
When they arrive, they find the duck sitting in a window box on the roof terrace, a day after her chicks hatched. The chicks are cowering under the shelf below the flower box.
The people who called for help are a retired couple in a third-storey flat and were pretty excited about the situation.
They watched as the duck kept balancing on the railing early in the morning, calling to her chicks. It seemed upsetting though this is normal behaviour for mother ducks, whose ducklings leave their nest just hours after hatching.
Happily, the couple had prepared their terrace well for this situation and had blocked up any cracks with boards to prevent any potentially deadly falls.
With the duck assistance team on site, the rescue operation kicked into high gear. Stelter offered the mother duck food to soothe her nerves before gently placing her in the bag.
"Her pulse is very steady," he said, gently stroking the bag. Engler meanwhile swiftly caught the chicks and placed them in his special transport box.
They headed to the car where they weighed, measured and ringed the duck.
Then they drove to water - in this case towards the old town of Köpenick on the Müggelspree, south of Berlin.
On the river bank, Engler opened up the box and after a moment's hesitation, the duck jumped into the water, followed by her offspring.
The family swam off, as though they had never been anywhere else but the water.
Staff at Berlin's wild bird centre have been rehoming duck families for more than 20 years, says Engler, a trained conservationist.
They are being called out more and more often. They received reports of 200 mallard broods last year, though the true number of ducks breeding close to humans is certainly far higher.
"Last year we relocated ducks in 159 cases," he says.
Ideally, though, the people who own the patio, balcony or backyard manage to bring the ducks to a safe place themselves. If necessary, they can be talked through the process by Engler or one of his colleagues on the phone.
Not all of the cases go as smoothly as the recent relocation in Adlershof. "Occasionally, a balcony is not so well secured so the chicks jump off. Or sometimes we can't catch the duck and we end up with just the chicks," says Engler. In that case, sometimes the ducklings might be adopted by another mother duck.
Berlin is surrounded by waterways and the team is most often at work in the districts of Spandau and Treptow-Köpenick, both on the outskirts. But occasionally they are called into the downtown area, too.
Alongside providing practical assistance, Engler and his colleagues are also researching the question of why ducks breed in these unusual places in the first place - and then keep coming back to them year after year.
"It is possible that there is no longer enough sheltered space on the waterways and the disturbance caused by people and dogs is too great. Dogs often scare off ducks breeding near the shore," says Engler.
Although the relocation assistance helps the creatures, there is also a risk that the ducks will become too accustomed to this service in the long term.
Ideally, owners of balconies should go out into the space as often as possible to discourage the ducks, is the recommendation of the German Animal Welfare Association.
"If you notice that ducks are interested, keep rearranging your plants and furniture, so the ducks don't see them as possible cover," is the official advice.
