Although House Finches (Carpodacus mexicanus) and House Sparrows (Passer domesticus) are distinct taxonomically, they share several ecological and behavioral similarities. Both are gregarious and are semi-colonial nesters, defending only a small, variable territory surrounding the nest (Thompson 1960a, Summers-Smith 1963). Both species are conspicuously well adapted to man-modified habitats and regularly build nests on manmade structures. Further, numerous observers have reported interspecific conflict between the two species involving nest sites (Gilman 1908, Bergtold 1913, Evenden 1957, and Thompson 1960a). Both species feed extensively in a group and overlap considerably in food selection. The diet of the House Finch