Declines in the populations of many songbirds that breed in mature forests have raised conservation concerns and fueled opposition to even-aged timber harvests on public lands. However, what those birds do after breeding, but before migration, remains poorly known, yet is a critical time in avian life cycles. A Forest Service research study conducted in northwestern Pennsylvania during the summers of 2005 to 2008 used mist-netting to capture birds in mature forests and regenerating even-aged harvests. Captured birds were banded and their physiological condition assessed. Based on almost 4,000 captures of 54 species, researchers found that most mature-forest species were much more common in harvests than in mature forests post-breeding. Further, birds caught in harvested areas were generally further advanced in molt and in better physiological condition than birds caught in forests, suggesting they increase their fitness by shifting their activities to regenerating cuts after breeding. These results indicate that early-successional habitats created by timber harvests are providinge an important resource for many mature-forest birds.