Increased risk of lek loss, resulting decline in active leks (%), decline in males on remaining active leks (%) and resulting chi-square tests between control leks with no development and those inside of 4 categories of increasing oil and gas development, by Sage-Grouse Management Zones I and II 19

aNumber of producing oil and gas wells within a 32.2 km2 (3.2-km radius) of a lek and average spacing between adjacent wells (ha and ac).
bIncreased risk of lek loss associated with increasing levels of development. For example, risk of lek loss was 5.1 times greater inside than outside of development in Zone I when densities were 40–100 wells per 32.2 km2.
cEstimates include a time-lag affect because it takes 4 years for impacts to manifest into population declines (File S1). Estimates also are adjusted for background losses not attributable energy development.
dIncreasing proportion of leks that go inactive with increasing levels of development.
eDeclines in active leks (%) and in males on remaining active leks (%) can be applied to assess trade-offs of newly proposed or ongoing development. Resulting declines in bird numbers form the biological basis for negotiating offsets.
fChi-square test not performed if sample size <5.