A long-term, volunteer-based nest-box program for American Kestrels (Falco sparverius) breeding in eastern Pennsylvania was evaluated to identify ways to increase the efficiency of the program and to identify general principles that can be used to improve long-term conservation efforts for other nest-box programs. Between 1993 and 2002, Hawk Mountain Sanctuary volunteers maintained and monitored approximately 270 kestrel nest boxes. Reproductive parameters of kestrels in these nest boxes were similar to those reported in other studies, and kestrels attempted nesting twice in a single year on 11 occasions. Nesting success varied among nest boxes, and productivity was consistently high at some nest boxes and consistently low at others. As a result, approximately half of all nestlings came from the 25% of nest boxes that were used most frequently, and fewer than 7% of kestrels fledged from the 25% of the nest boxes that were used least frequently. Our analysis suggests that volunteer field effort could be reduced by 25% with minimal impact on overall kestrel productivity. Managing for increased conservation efficiency is not inconsistent with effective conservation monitoring and management of kestrels. Our findings have important implications for conservation efforts in which substantial benefits can accrue from more efficient use of limited conservation resources.