Seasonal Variation in Habitat Use by Great-Tailed Grackles in the Lower Rio Grande Valley

Habitat use by great-tailed grackles was measured by performing weekly censuses of birds in 6 different habitat types: chaparral, citrus groves, feed lots, pastures, residential areas, and agricultural fields. We found that use of chaparral, citrus, and residential sites was low during the winter months, increased sharply with commencement of the nesting season in April, and declined again by October. Use of agricultural fields and pasture was irregular. Feed lot use was low during the summer, but high from October - April with October and March migration peaks. An overall sex ratio of 1.3 females/male was observed with skews from this ratio related to the different life history requirements of the sexes