Oil and gas roads fragment habitat. I took Renewable Resource Management with a Conservation Enforcement specialty in College. One field trip we took to watch the mating dances on a "lek". The oil and gas roads also plow under more of the tall mature sage the birds require.
The instructor mainly blamed the lack of prairie fires and livestock grazing in the mature tall sage the grouse use for shelter. Cattle knock down the brush and graze the grass short reducing the hiding cover (mainly when the hens are on the nest). Fire required to rejuvenate the sage, otherwise it gets quite woody and not as much succulent browse.
Anyways that is what I remember from an early morning in April 1989.
