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 energy 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 measured apparent chitin digestibility (Dchitin = 1 - chitin excreted/chitin ingested) in both species and tested the predictions that (1) Dchitin would be higher in bobwhites than robins, and (2) Dchitin would be higher in robins after acclimation. Dchitin ranged from 0.07-0.14 with no significant difference between or within species, so both predictions were rejected. These apparent chitin digestibilities are low relative to values reported for seabirds that eat krill, and account for < 1% of the metabolizable energy in crickets.