The efficiency with which an animal obtains energy from its diet is critical to its survival during stressful periods (e.g. winter in terperate zones). We determined the variance in digestive efficiencies among four winter sympatric bird species: the Northern Cardinal (Cardinalis cardinalis), Dark-eyed Junco (Junco hyemalis), Harris' Sparrow (Zonotrichia querula), and American Tree Sparrow (Spizella arborea). These species are granivorous birds characterized by strong beaks adapted for cracking seeds (Bent 1968). Of the four species, only the Northern Cardinal ia a year-round resident of Kansas