As boaters flock to Minnesota lakes on the July 4th weekend, conservation leaders are warning them to watch out for loons to avoid hitting the state bird.

The Minnesota Department of Natural Resources (DNR) issued the reminder this week ahead of the busy boating weekend, noting that watercraft are a significant cause of loon deaths.

Minnesota has an estimated 12,000 common loons — more than any other state except Alaska. Loons frequently nest and raise their young in areas where boaters may be speeding by, and loon chicks can't dive for safety or fly until they are more than 2 months old, the DNR says.

With the help of volunteers, the DNR monitors the population of the black and white birds known for their haunting calls. This summer, the DNR launched a new online system for the volunteers, funded by a donation from the Minnesota United pro soccer team, which is nicknamed the Loons.

Volunteers are conducting the annual loon count through July 8 on lakes throughout central and northern Minnesota. The count helps detect changes in the adult loon population and anticipate problems that could affect the future of the state bird.

Besides being hit by boats, the loon population is threatened by pollutants such as lead and mercury. Environmental groups also say that, by the end of the century, loons could disappear altogether from most of the Great Lakes because of climate change.

A nonprofit group plans to build a National Loon Center in north-central Minnesota to help conserve habitat and raise awareness about loons.