This study examines the relationship between Red-cockaded Woodpecker (Picoides borealis Vieillot) reproduction and rainfall during May when group members are provisioning nestlings with food. Patterns of variation over a 4-year period of approximately 30 woodpecker groups suggested that the mean number of hatchling deaths was positively related to the amount of rainfall that occurred during May. During the same 4 years, the mean number of young fledged from nests appeared to be inversely related to May rainfall. Observations of nestling provisioning behavior during four breeding seasons indicate that group members slow down or stop feeding nestlings during periods of heavy rainfall. During a 20-year period, total May rainfall was related to the percentage of woodpecker groups producing fledgling-sized young in cavities (r_s = −0.56, P = 0.0097) and the occurrence of El Niño events (r_s = −0.50, P = 0.0347).