Food habits of Double-crested Cormorants wintering in the Delta region of Mississippi

The diet of Double-crested Cormorants (Phalacrocorax auritus) wintering in the Delta region of Mississippi was studied from collections of 202 birds taken at catfish farms during the winters of 1987-88 through 1989-90, and fi om collections of 461 birds at night roost sites during the winters of 1989-90 and 1990-91. Channel Catfish (Ictalurus punctatus) and Gizzard Shad (Dorosoma cepedianum) were the only two important prey species, comprising >90% of the diet from all samples. However, the proportion of these two prey species in the diet varied dramatically (P<0.05) among months and geographic locations of collections, as well as between sexes of birds collected. Overall, the diet was approximately equal between catfish and shad, but catfish was most often consumed by males during the spring months in the areas of highest catfish concentration. The size range of catfish preyed upon appeared to parallel the size class of fish used for stocking commercial ponds in the spring. Based on these analyses, we recommend strategies for reducing cormorant predation on commercial catfish.