New Delhi, April 7 -- As night falls over a nature park on the edge of Kyiv, children crowd around volunteers who carefully open cloth bags and release bats into the twilight.

As each one takes flight, snapping through the air, more than 1,000 spectators cheer and applaud - families, off-duty soldiers, and bat enthusiasts, a few dressed in Goth outfits.

Hundreds of bats, many rescued from war-torn areas in the east of the country, were released late Saturday at one of multiple events around Ukraine planned to coincide with the arrival of spring.

"This is important for us as an organization because these are on a red list of endangered animals. Preserving them is very important," said Anastasiia Vovk, a volunteer at the Ukrainian Bat Re...