Michigan wildlife officials are seeking the public's help to determine how many trumpeter swans live in the state.

It's part of a census covering the entire continent.

Trumpeter swans historically nested in wetlands across the U.S., but hunting and habitat loss nearly drove them extinct in the late 1800s. Restoration efforts in Michigan began a century later.

A count in 2004 turned up 655 trumpeters statewide. The greatest numbers are found in the eastern Upper Peninsula. They're still listed as a threatened species.

The Department of Natural Resources and Environment is asking people to report sightings of trumpeter swans in August and September. They should not be confused with mute swans, which have bright orange bills while trumpeters have black bills.