Climbing will be restricted on Granite Mountain and Thumb Butte for nesting peregrine falcons.
Prescott National Forest officials say the sites have been occupied annually by peregrines for years. The closure gives the birds a chance to raise their young undisturbed.
The peregrine was once listed under the Endangered Species Act and is still protected under state and federal law.
Climbing will be prohibited on any part of the Granite Mountain rock cliff face or above the rim. On Thumb Butte, the north and south climbing faces, top and the areas at the base will be closed.
The restrictions start Thursday and will last through July 15.
Forest officials also ask for local birders to share their field observations of the peregrine falcons to provide a better picture of their nesting progress.