CORRECTION: No actual trails are being closed, just off-trail areas in the vicinity of the listed trails.

Starting Thursday and running until July 31, Boulder's Open Space and Mountain Parks Department will begin seasonal closures in an effort to protect grassland ground-nesting birds.

The areas closed include off-trail areas, but not the trails themselves, around parts of the Greenbelt Plateau Trail, Community Ditch Trail, Flatirons Vista North Trail and South Boulder Creek West Trail. 

Maps and additional information can be found at

The move follows reports of North America's grassland bird populations falling sharply over the last few decades. Three species that Boulder monitors -- grasshopper sparrows, horned larks and lark sparrows -- have all suffered at least a 50 percent drop in the last 40 years, the National Audubon Society says.

"The closures OSMP will implement Thursday are important in protecting these species' habitats by keeping people and their pets away as the birds attempt to nest," a news release from the city reads.

Trespassing on the closed trails could result in up to 90 days in jail and a $1,000 fine.