The effects of prescribed fire on interactions between birds and ticks

Fire is a natural ecosystem process whose effects on tick-borne disease systems vary across ecosystems, fire regimes, and tick species. Most studies focus on fire’s effects on populations of host-seeking ticks, but little is known about how fire affects interactions between ticks and their vertebrate hosts, a key determinant of pathogen prevalence. We investigated how prescribed fire influences tick burdens on passerine and near-passerine bird hosts using a landscape-scale field experiment that included 16 paired 2.5-ha treatment and control plots in the Missouri Ozarks ecoregion. Treatment plots were burned in 2017 and we sampled birds from 2017 – 2019, assessing their tick diversity and burdens. We captured 302 birds representing 25 species and collected 1,491 ticks from 137 of those individuals. The most frequently captured species were Thryothorus ludovicianus, Parkesia motacilla, and Cardinalis cardinalis; ground foraging species had the greatest tick burdens and tick burdens varied by bird age. Ixodes scapularis comprised the majority of ticks collected from birds, despite Amblyomma americanum being the most frequently encountered host-seeking tick in the plots (dry ice traps). We observed a significant reduction in numbers of larvae and nymphs parasitizing birds in 2017 immediately after the prescribed burns, followed by recoveries in 2018 and 2019. Larval tick burdens increased between years more rapidly than nymphal tick burdens; in 2019 larval (but not nymphal) tick burdens in previously burned plots matched those in control plots. Understanding tick-host interactions can help inform land management strategies for tick-borne diseases and complement studies of free-living tick ecology.