Rigorous state-wide monitoring programs are lacking for dusky grouse (Dendragapus obscurus), a North American species of forest grouse with relatively low detectability that is found in coniferous and mountainous areas in the western United States and Canada. Hierarchical models for estimating abundance show promise for overcoming issues associated cryptic forest grouse behavior and low population densities. Our objectives were to evaluate protocols (i.e., number of sites, visits, and route type) and analytical methods for producing annual unbiased and precise indices of abundance (CV < 15%) to inform a statewide monitoring program. During 2019–2022, we designed and implemented multiple survey protocols throughout western Montana, USA, including spring point-counts (> 2200 unique sites) and transect-level (> 390 unique transects) distance sampling. We used an iterative process of field data collection and simulation analyses to evaluate the performance of four different statistical estimators for abundance (N-mixture model, hierarchical time-removal model with distance sampling, detection-naïve model, and hierarchical distance sampling model) for point-counts and transects to produce unbiased and precise estimates of dusky grouse abundance. Simulations demonstrated that increasing the number of sites visited or probability of detection decreased the requisite amount of survey effort for obtaining precise abundance estimates for all estimators. Unbiased and precise estimates of abundance were unachievable under most realistic point-based distance sampling protocols. N-mixture protocols where point-counts conducted during periods of high probability of detection at 80 sites visited four times per area of inference (e.g. study area or region) resulted in unbiased estimates of population size with the highest precision. Our study provides baseline information necessary for the development of state-wide monitoring programs of dusky grouse and more broadly illustrates an approach for developing rigorous and achievable monitoring programs for other species of forest grouse.

Despite status as a game species in the western United States, rigorous monitoring of dusky grouse (Dendragapus obscurus) populations is limited. Obtaining an adequate number of observations for effective population monitoring of dusky grouse is challenging due to difficult-to-reach montane habitats, cryptic behaviors, and limited personnel, time, and funds at conservation agencies. While habitat accessibility and survey effort constraints may be outside a manager’s control, identifying the most effective protocols to better detect a target species is possible and will improve monitoring programs. Our objectives were to 1) evaluate field-based protocols for maximizing dusky grouse detections and 2) identify survey conditions and timing that maximize the probability of detecting dusky grouse in western Montana. We conducted replicated point-count surveys with and without electronic playback in spring and summer 2019, and spring surveys solely with electronic playback in 2020–2021. We used N-mixture models to compare the probability of detecting dusky grouse in spring verse summer sampling, and evaluate the effects of electronic playback of grouse calls, route type (off-trail, trail, and road), weather, background noise, day, and time on probability of detection. Spring sampling yielded significantly more dusky grouse detections than summer sampling. The use of electronic playback of female calls in the spring increased detection probability but chick distress calls during the summer did not improve detection rates. The probability of detecting a dusky grouse was similar across the different route types (off-trail, trail, and road), and maximized on clear days, with little wind and background noise, with surveys occurring 9–162 minutes post-sunrise during 3–23 May. By examining the effects of different factors on dusky grouse probability of detection, our results provide necessary information for the development of effective protocols for field surveys for population monitoring of dusky grouse.