Ecosystems support intricate food webs where changes to a plant or animal population can ripple out to impact many other species. That’s the case for the spruce budworm, a native moth found in North American coniferous forests. During their outbreaks, which can last 10 years, these caterpillars defoliate and kill vast stretches of spruce and fir trees. This summer, their numbers were again large, impacting forests in Canada, Maine and Minnesota, among others.
How is the ongoing spruce budworm outbreak impacting birds? It was an all-you-can-eat buffet for insectivorous birds during their breeding season, and young birds had ample food during the summer. But looking ahead to colder months, birds like the Purple Finch won't have their normally abundant seed supply since the decimated trees did not produce a strong seed crop. As a result, the Winter Finch Forecast predicts that birds will seek food by moving out of affected areas.
Understanding spruce budworm outbreaks is the focus of recent research, with groups modeling and studying the insects’ large-scale dispersal, how habitat loss impacts outbreaks, how defoliation affects nearby streams and habitat for caribou, moose and their predators, and how the ecosystem recovers from an outbreak.