The company says the two-year project will support 150 jobs, and will begin with on-site roadworks to allow delivery of its Gamesa wind turbines.
Iberdrola-owned ScottishPower obtained planning consent for the £160m ($258m) project in 2007 following a public enquiry.
The completed wind farm will see 11km of new tracks and paths opened to members of the public, including two new mountain bike trails, funded by ScottishPower Renewables.
Harestanes
