Abstract
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.