I am working with the USFWS to develop a range-wide a monitoring plan for the federally endangered Fender's Blue Butterfly. The species is found only in the Willamette Valley prairies of western Oregon. Monitoring of the adult Fender's Blue is complicated by a short one month flight season characterized by intermittent periods of appropriate survey weather and the presence of dozens of isolated populations scattered across a 1,000 square mile region. In addition, the Fender's Blue occurs sympatrically with the morphologically similar and common Silvery Blue Butterfly. Distinguishing the two species in flight is difficult for even the experienced observer. I am currently working to pilot a hybrid Distance-sampling based (at intensively managed) and peak count approach (at outlying sites) to balance precision to detect management impacts and to meet information requirements for recovery criteria set by USFWS with cost and logistical feasibility. Pilot work began in the spring of 2010 and will continue through 2012 to inform monitoring design within the context of a structured decision analysis.