Notation and description of a candidate set of models for evaluating spatial and temporal patterns in density estimates (from program DISTANCE) of four species of grassland and early successional habitat in northwestern Arkansas during 2003. Models include treatment effects (TRT) of unhayed (n = 3), early-hayed (n = 2), and late-hayed fields (n = 4), time effects (Time) during count 1 (18–23 May), 2 (12–15 June), or 3 (7–14 July), and effects of distance (km) of fields to nearest residence.