Demographic response of Northern Bobwhite to hardwood canopy management in pine savanna

Disruption of historic fire regimes has led to the expansion of hardwoods into pine savanna ecosystems in the southeastern United States. Management strategies that reduce mature mesophytic oaks in pine savanna that was previously fire suppressed may help restore understory vegetation and positively affect understory birds. Many private lands in the Southeast are managed intentionally for the Northern Bobwhite (Colinus virginianus; hereafter bobwhite), a species with high cultural and economic importance to the region. Mechanical hardwood reduction is used to restore southeastern pine savanna and as a predation management tool to enhance populations of bobwhite although its utility has not been empirically tested. We measured the demographic response of bobwhite to a large-scale hardwood reduction using a before-after-control-impact (BACI) study replicated at two properties in the Red Hills region of northern Florida, United States, that had a relatively low density of mature, mesophytic hardwoods and were already managed for bobwhite with 2-year fire return intervals, supplemental feeding, and meso-mammal control. We monitored reproduction at 561 nests and survival of 1529 adults tracked with radiotelemetry. In treated sites, mean daily nest survival was 0.98 and did not change following hardwood reduction. Reproductive effort declined each year (pre- and post-treatment; 2015-2018) in one treated site and varied relatively little in the other. At both treated sites, weekly adult survival decreased to 0.93-0.94 immediately following the treatment, then increased gradually but did not exceed pretreatment weekly survival (0.98) within 2-3 years following the treatment. Our results suggest hardwood reduction may not benefit bobwhite adult survival or productivity within 2-3 years of application on sites that are already managed intensively with prescribed fire, predator control, and supplemental feeding and that hardwoods in this system may not have direct negative impacts on understory birds. Further study is necessary to determine under what conditions hardwood reduction may be beneficial and whether other metrics such as chick survival or immigration are affected. Our study sites represent typical land management in the Red Hills region, and we believe the inference of this study extends at least to properties with similar management schemes and similar bobwhite population density.

Automated summary

Disruption of historic fire regimes has led to the expansion of hardwoods into pine savanna ecosystems in the southeastern United States. Management strategies that reduce mature mesophytic oaks in pine savanna may help restore understory vegetation and positively affect understory birds, but the impact on bobwhite survival and productivity remains inconclusive following hardwood reduction.