-We conducted experiments to determine the effect of time postmortem, feeding activity, and diet on changes in digestive organ morphology in Dark-eyed Juncos (Junco hyemalis) and Harris' Sparrows (Zonotrichia querula). We measured digestive organs immediately, or at 30, 60, or 90 min postmortem, but detected no time-related differences in Darkeyed Juncos. The small intestines of free-feeding Dark-eyed Juncos were longer than those of food-deprived birds. We found no significant diet-related differences in lengths of small intestines of Harris' Sparrows. Liver mass reflected energy intake of free-feeding versus fooddeprived Harris' Sparrows. Received 4 August 1989, accepted 7 April 1990. THE AVIAN literature abounds with descriptions of changes in digestive organ morphology. Researchers attributed changes in avian gizzard size to the texture and fiber content of the diet (Ziswiler and Farner 1972, Savory and Gentle 1976a, Kehoe and Ankney 1985), and reported a relationship between gizzard mass and body mass in northern Galliformes (Thomas 1984, Moss 1983). Leopold (1953) and Kehoe and Ankney (1985) suggested that a high-fiber diet causes increased lengths of small intestines, a conclusion reached by several researchers working on tetraonids (Moss 1974, Pendergast and Boag 1973, Pulliainen and Tunkkari 1983). A causal relationship between cecal size and dietary fiber was proposed (Leopold 1953) and supported with experimental evidence (Moss 1972, 1989; Savory and Gentle 1976b; Moss and Trenholm 1987; but see Remington 1989). Ziswiler and Farner (1972) contended that largeintestine length reflects the diet of avian species, and Savory and Gentle (1976a, b) could produce increases in large-intestine length by adding fiber to the diet of Japanese Quail (Coturnix coturnix). Most pertinent reports on avian species have involved gallinaceous birds and waterfowl. Little attention has been focused on changes in gut morphology of passerines, or the influence of time postmortem or feeding activity on measurements of gut morphology. In this study, we examined the effects of time postmortem, feeding activity, and diet on digestive organ morphology of two emberizids, Harris' Sparrow (Zonotrichia querula) and the Dark-eyed Junco (Junco hyemalis).