Amy Ray and Emily Saliers--a.k.a. Indigo Girls [ tickets ]--head out in April on a speaking tour during which they will give short acoustic performances.

Ray and Saliers are teaming up with Native American environmental activist Winona LaDuke--the Green Party's 2000 vice presidential candidate--for the eight-date outing, which will make stops at college campuses in Minnesota, Idaho, Washington, Oregon and Colorado. The tour wraps up on Earth Day, April 22.

Dubbed the Honor the Earth tour, the outing is billed as a "speaking and performance tour aimed at educating college students and the general public on current issues related to Native environmental activism and the development of wind power on Native lands, in particular," according to a press release.

Net proceeds from the tour will be directed to the Energy Justice Initiative, which will subsequently use the money to provide capital and technical support for wind projects on Great Plains reservations.

Prior to the April 15 start of the Honor the Earth tour, Indigo Girls will appear in Atlanta on March 22, where they--along with Sister Hazel and Edwin McCain--will perform at the Lyrics for Life benefit show.

Two early-April acoustic performances are also planned, and will feature an opening performance from Kim Richey.

Indigo Girls most recent release is "Become You," which hit stores early last year. Further details about their upcoming touring activity is posted at their website.