Spruce budworm boom linked to spikes in boreal bird sightings, Maine Audubon says

Nick Lund, advocacy and outreach manager for Maine Audubon, told a local audience that cyclical outbreaks of the eastern spruce budworm have driven historical booms and busts in several boreal bird species in Maine and that the present outbreak in northern Maine offers a chance to monitor those effects.

Lund said long-term data show heavy increases in sightings of evening grosbeaks and several warblers during past spruce budworm outbreaks. "When there was this big outbreak of spruce budworm, insects and caterpillars especially being the best food for baby birds, that meant that even grosbeaks had a ton of food to feed their babies and so there were a lot more evening grosbeaks," he said. He cited documented outbreak periods in the 1910s, the 1940s and the 1970s–80s.

Why it matters: budworm control decisions by foresters and the timber industry can change food availability for insectivorous birds, with direct effects on breeding success. Lund said contemporaneous monitoring of bird counts during the current outbreak can test the linkage and inform management choices.

Lund urged managers and the public to consider those ecological tradeoffs when evaluating spraying or other control measures. "We can, as Maine Audubon, weigh in and try to inform spraying regimes or other ways that people are trying to control for spruce budworm," he said, noting that foresters and industry already actively manage the pest.

The presentation said observers are already seeing increases in species tied to budworm outbreaks — such as bay-breasted, Tennessee and Cape May warblers — and recommended continuing systematic surveys and cross-checking breeding-atlas and Christmas Bird Count data to measure population responses.