Who sits poison-greenly in the treetops of Cologne? The parrot! Also known as the cockatiel. 4,000 of these exotic verdant warblers live in Cologne. Rocketing through the area at 70 km/h, they pollute the city with poop, attack trees with their beaks and, to add insult to injury, squawk. Are these Asian collared parakeets perks or pests, enrichment or imposition? The documentary by the renowned Berlin biologist and nature filmmaker Ostwald explores this question and produces some interesting findings. The species has adapted amazingly quickly to its new living conditions.