Years of complex legal wrangling with conservationists were triggered when an ornithologist being treated at the hospital several years ago reportedly heard the male bird singing outside his window.

The nightjar, a protected species, is called Ziegenmelker, “goat milker”, because of an ancient myth that it suckles from goats. The clinic had been declared a “nightjar habitat” because the bird had regularly been spotted on the roof of the building.

Mayor Boris Palmer said the delay was driving him mad.

“I’d love to sign the building permit. But then I’d go to jail,” he said in a rant on a TV talk show.

“The nature conservation authority says, ‘You can build, but you first have to create an alternative habitat for the bird.’ Doesn’t sound too bad at first. But nightjars are an open land species. They need wide-open spaces that they can fly through. That’s why they are bothered by trees.”

Conservationists proposed cutting down 25 acres of forest behind the hospital so that the bird could roam freely there, he said. “I’m already looking forward to the public debate when I cut down 1,000 mature trees. I’m already getting petitions when it’s just about a single tree!”

Palmer said his hopes had lifted after a year without any sightings of the bird.

“I thought: a cat got him. Problem solved,” he hoped. “The conservationists said: ‘If there used to be a nightjar there, then it’s nightjar expectation land. You have to act as if it’s still there and cut down the forest’.”

Palmer said that he had written to the state government of Baden-Württemberg asking whether an official could be found to issue a death certificate for the bird. “The district administrator, the state prime minister, the regional president, we write letters to each other all the time. They are just as baffled as I am. Even as prime minister, you can’t say: ‘That’s the end of it’.

“The bird is so strictly protected that criminal law prevents common sense from prevailing. And that is damaging to democracy. How am I supposed to explain that to the public? They all say that the state no longer works.”