TOWN OF OMRO - The Department of Natural Resources is investigating vandalism on the west end of Lake Butte des Morts in Winnebago County.
A tiny man-made island was home to this year's nesting colony of an endangered bird called the common tern.
Now, it's a crime scene.
Wardens from the Department of Natural Resources combed the island Friday. The searched for clues and picked up evidence.
"This is one of those unique calls that you just don't deal with every day," said April Dombrowski, DNR Warden Supervisor.
Dombrowski says a nesting colony of common terns was vandalized Tuesday night. About 25 chicks were killed.
"Some of them could have been smashed between rocks, and possibly with them on the ground, stomped on type of things. Human activity involved," said Dombrowski.
The DNR says the terns were two days to three weeks old. The chicks were found when biologists came to the island to put research bands on the young birds.
Wildlife biologists say the birds prefer to breed near large bodies of water. They say there are only five nesting sights in the entire state.
"Where this happened was actually one of the constructed ones. An island that was built a few years ago using funds from the natural resource damage assessment to provide habitat for the common terns," said John Huff, DNR Area Wildlife Supervisor.
DNR officials say the adult terns left the colony. It's unclear if those birds will nest on the island again.
"I would hope so, but there's no guarantees. Once the adults abandoned the site it's another matter of getting those adult common terns to return," said Dombrowski.
Wardens say the the investigation is in its early stages. They say whoever killed the chicks had no business on the tiny island.
"You always ask the question why, why would someone go through the energy to do something like this," said Dombrowski.
The DNR is hoping anyone with information about the vandalism on Lake Butte des Morts will contact them.
Click here for the link to the agency's tip-line.