Although hoarding has been studied intensively for many decades, few studies have attempted to measure its actual fitness consequences. To fill this gap, we used ptilochronology, the growth of replacement feathers as a measure of nutritional status, and thus a reflection of starvation risk, of individual European nuthatches (Sitta europaea) during winter. We found that nuthatches are long-term hoarders, retrieving stored food up to at least 98 days after storing it. Long-term hoarding enhanced the nutritional status of individual birds significantly because those individuals experimentally given an opportunity to store seeds during autumn regrew plucked rectrices faster and larger than did control birds. Nuthatches used their stored seeds prudently by adjusting the amounts they ate to meet their requirements, as determined by ambient temperatures. Nuthatches refrained from using stored food during periods of relatively benign conditions so they could use the food during periods of more severe conditions.