Examination of wing-feather molt often provides information essential for aging birds in the hand (Mulvihill 1993, Pyle 1997b, 2008). Correctly aging birds is important for understanding the causal relationships between age-class survival rates and population changes (DeSante et al. 2005). For example, correctly aging birds facilitates understanding of climate effects on reproduction better than merely monitoring population numbers because reproduction varies widely with annual weather patterns (DeSante and O’Grady 2000). Age-class information can also provide a clear measure of habitat quality without confounding effects such as population sources and sinks (Van Horne 1983) or misleading habitat-quality information based on relative abundance or population size (Pulliam 1988). Changes in bird populations often lag changes in the survival rate of an age class, while environmental changes often affect one age class immediately or after a short lag (Temple and Wiens 1989).