When a wildlife specialist climbed onto Nassau University Medical Center’s 17th-story window ledge Monday, he had hoped to find five newborn falcons, but discovered only one.

It’s not known why four of the eggs, laid several weeks ago, failed to hatch, said the specialist, Christopher A. Nadareski of the New York State Department of Conservation.

“We don’t know the reason why,” he said. “We’ll have the eggs analyzed.”

Nadareski believes that cold weather was to blame.

Meanwhile, officials at the East Meadow hospital named the newborn peregrine falcon Mickey. The bird was removed from its nest, tagged, then put back.

In about three to four weeks, the newborn falcon will take its first flight, Nadareski said, assuming the bird doesn’t crash into cars or other hazards.

advertisement | advertise on newsday

Peregrine falcons are listed as endangered species, but thanks to conservation efforts their population has grown over the years. There are now about 30 pairs of adult falcons in the metropolitan region.

“It used to be unique,” he said. “The population is growing and doing quite well right now. We have them on bridges, buildings and marshes.

Since 1997, more than 60 falcons have been born at the hospital, said spokeswoman Shelley Lotenberg.