DIGESTION OF CHITIN BY NORTHERN BOBWHITES AND AMERICAN ROBINS

Northern Bobwhites (Colinus virginianus) were acclimated to crickets, and food intake and excreta output measured. Their metabolizable energ y coefficient (MEC = 1 - energy excreted/energy ingested = 0.77) was significantly higher than that of American Robins (Turdus migratorius) that were unacclimated or fully acclimated to eating crickets. We mea sured apparent chitin digestibility (D-chitin = 1 - chitin excreted/ch itin ingested) in both species and tested the predictions that (1) D-c hitin would be higher in bobwhites than robins, and (2) D-chitin would be higher in robins after acclimation. D-chitin ranged from 0.07-0.14 with no significant difference between or within species, so both pre dictions were rejected. These apparent chitin digestibilities are low relative to values reported for seabirds that eat krill, and account f or < 1% of the metabolizable energy in crickets.