Low Mitochondrial DNA Variation in Double-crested Cormorants in Eastern North America

—Double-crested Cormorant ( Phalacrocorax auritus ) numbers are increasing throughout eastern North America. We compared variation for five portions of mtDNA to determine if genetic differences existed among portions of the breeding range that would need to be considered when formulating management programs. Sequences for four mtDNA regions were identical across sample locations; frequencies of two haplotypes of the mitochondrial Control Region were similar across sampling locations. There is no evidence of restricted gene flow among breeding areas, or between subspecies with different migratory patterns. Received 6 June 2002, accepted 25 November 2002.