Occupancy patterns of spruce budworm-linked warblers in response to the application of Btk

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University of New Brunswick


Btk (Bacillus thuringiensis kurstaki) is an insecticide used to manage spruce budworm (Choristoneura fumiferana; hereafter “SBW”) in New Brunswick, Canada. No study has yet assessed Btk’s impact on habitat occupancy by “SBW-linked warblers” such as Baybreasted (Setophaga castanea), Tennessee (Leiothlypis peregrina), and Cape May Warblers (S. tigrina). To control SBW populations, Btk is applied to “hotspots” of increasing populations and in these locations, I studied how SBW-linked warblers respond numerically to Btk application. Using autonomous recording units (ARUs) and avian point count surveys, I discovered that Cape May Warblers were the most prone to vacate Btk-treated territories (z=-14, p=2.0X10 -16), Bay-breasted Warblers vacated territories at a lesser rate, while Tennessee Warblers were the least numerically sensitive to Btk application. Finally, I argue for the efficacy of using both point counts and ARUs for data collection in studying occupancy, even though ARUs provide much larger datasets amenable to multi-variate modelling.