ADVANTAGES OF COLONIALITY IN FEMALE BOAT-TAILED GRACKLES

摘要

In a South Carolina cattail marsh, female Boat-tailed Grackles (Quiscalus major) concentrated to nest on predator-safe islands patrolled by American alligators (Alligator mississippiensis0. I examined several hypotheses regarding colonial nesting behavior of Boat-tailed Grackles. (1) I reject the null hypothesis that conony-nesting and solitary females do not differ in reproductive success. Solitary-nesting females had lower reproductive success (37/100) than colony females (63/100), a difference perhaps attributable to males' defense of colonies from predatory birds. (2) I reject the hypothesis that the physical characteristics of sites used for colonies differ from those that are not used.