We evaluated flight feather molt of Common Grackles (Quiscalus quiscula) collected in North Dakota to determine differences by age and sex and to infer seasonal relationships with nesting and migration. On average, the HY preformative molt started and ended later than the AHY prebasic molt. Percentages of molting AHY males and females in weekly collections were ≥90% beginning the first and fourth weeks of July, respectively. Percentages of molting HY males and females reached ≥90% the first week of August. Both age classes remained >90% in molt through mid-September; thereafter percentages fell rapidly, likely caused by the passing of enough time from average onsets of molts for both resident and northern nonresident populations. By the first week of October, molting HY males and females comprised about 55% of weekly HY collections compared to 9% and 21% for AHY males and females, respectively. Extensive access to commercial sunflower fields perhaps allowed resident and nonresident AHY birds to remain in the area until molt was at or near completion.