Eastern hemlock forests have been declining due to a non-native insect pest, the hemlock woolly adelgid. A new study from The Condor: Ornithological Applications presents some of the best long-term data showing how the decline of a single tree species (eastern hemlock) leads to the disappearance of birds specialized to those trees. The data also indicate birds associated with non-hemlock habitat features (deciduous forest, woodland edge, and shrubs) are spreading into former hemlock forests. A single insect species has led to a less diverse bird community across this landscape.