Today I have heard a quak quak and thought I'm nuts. I asked my client if she hears it, too. She denied but than heard it also. Then I went outdoors in our courtyard and I saw a duck and two little ducklings. The janitor was there and told me that a crow has already killed one. And then we heard it plopping: Six ducklings jumped from the roof (around 8m) and landed on hard ground, some seem like they were severely damaged, squeeked without coming to their feet. Oh shit. We grabbed them and brought them to their mother. They were very fluffy and sweet. The more damaged tolerated the transport and came to their feet. One was on the wrong path and very agile in my hand. We brought them all to their mother, one had a broken neck - one killed by the crow. I called the wild animal rescue and they found and caught them and brought them to a safe water area. They sent us this photo.