The stomach contents of 402 adult male and 248 adult female red-winged blackbirds (Agelaius phoeniceus) were analyzed for their total dry weight and caloric values to determine daily rhythms and seasonal changes between June 24 and September 10, 1966. The stomach contents were analyzed qualitatively by identifying and estimating the proportion of each food type. The mean caloric value of food in male redwings showed three peaks during the day and was significantly (P < 0.01) higher before noon than after noon. Mean caloric intake of female redwings showed three peaks during the morning but no major peaks were demonstrated in the afternoon. Intake levels in the females were also higher in the morning. Mean caloric intake in June at the end of the breeding season was 211 cal/[bird gram × day] and in September, prior to autumn migration, was 246 [cal/bird gram × day]. Daily and seasonal peaks of the total energy intake represented changes in quantity of food consumed and changes in caloric content of ingested food.