Date of this Version
We compared the esophageal contents of adult male common grackles (Quiscalus quiscula), red-winged blackbirds (Agelaius phoeniceus),and yellow-headed blackbirds (Xanthocephalus xanthocephalus) collected in north central North Dakota from July through October 1989. Temporal variation in the diets of all species was related to food availabilities, which were heavily influenced by crop phenology. Depending on species, mean percent dry weight of sunflower achenes during August increased 2-6 times over July. Yellow-headed blackbirds migrated from north central North Dakota by early September, but substantial numbers of common grackles and red-winged blackbirds remained until mid-October. Sunflower was an important component of red-winged blackbird and common grackle diets through October. The more varied diet of yellow-headed blackbirds, in combination with the early departure from sunflower-growing regions, makes this species less likely to cause economic impact to the sunflower producer.