Tree cover limits occupancy of a declining game bird

Open forest ecosystems are considered one of the most imperiled ecosystems
in North America and many associated avian species are experiencing
population declines. Management at large and impactful scales is
challenging on private lands due to fragmentation and resource
limitations, but public lands are often larger in scale and offer
opportunities for landscape level conservation of species of conservation
concern. Northern bobwhite (Colinus virginianus; bobwhite) is a popular
but declining game bird which is often considered an umbrella and
indicator species for savanna ecosystems. To evaluate the effects of tree
canopy cover and prescribed fire frequency (1 Jan 2010 – 15 May 2024) on
bobwhite occupancy we surveyed 144 sites 11 times during 15 May – 17 June
2024 using acoustic recording units on the Sabine and Angelina National
Forests of Texas. Probability of bobwhite occupancy decreased as canopy
cover increased (βTree = -0.74, 95% CrI: -1.29 – -0.28); occupancy was
over 19 times higher when canopy cover was 44% versus the mean observed
value of 80.8% (range: 38–96%). Despite a well-established positive
relationship of bobwhite and prescribed fire based on previous research,
we found tree canopy obfuscated any effects of fire frequency on bobwhite
occupancy (βFire = -0.09, 95% CrI: -0.57 – 0.43). Only 2 of 144 sites were
characterized by low-moderate canopy cover (<50%) with a moderate
fire frequency (burned 5 and 7 times since 2010). Our results underscore
the importance of forest thinning in addition to prescribed fire for
managing species which require savanna conditions.