Bird and beetle assemblages in mountain pine beetle killed forests and those subsequently burned: evidence for an effect of compound natural disturbances in British Columbia

The recent mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) outbreak in British Columbia (BC) is unprecedented in severity and extent, and has created a landscape of beetle-killed trees through which wildfires are now burning as compound natural disturbances. We asked the question: Is there an impact of grey phase MPB kill severity on bird and beetle assemblages, and does an effect persist following wildfire in BC? We compared the bird community of central interior BC against categorical and continuous disturbance severity gradients in unburned (MPB-only) and burned (MPB+FIRE) forests. Bird abundance and diversity was higher following fires, possibly supported by foraging resources from the positive abundance of beetles, however our findings suggest intermediate severities of compound disturbances show the greatest increases. In MPB-only areas, cumulative MPB kill was generally unimportant at the stand scale, but local gradients played a role in describing guild patterns, bird community membership, and single species abundances. In comparison, both burn severity and underlying MPB kill were important predictors in MPB+FIRE stands, suggesting evidence of a compound disturbance effect. We observed tenuous patterns that suggest the MPB outbreak might have detrimental effects on avian bark insectivores post-fire, but a positive influence on aerial foraging species. Further research is required on available resources for these guilds after compound MPB and wildfire disturbances.