The model is initialized with a population of approximately 300 sparrows reflecting a composite of the distribution of sparrows from 1993, 1995, 1996 and 1997. These sparrows are placed across the landscape and assigned to territories if available. If no territories are available, the individuals are labeled as "floaters" within the 500 meter cell. The age of each individual is chosen randomly from a decaying binomial distribution of ages representing a stable class distribution. The model then tracks each individual on a daily basis during the breeding season as it responds to its territories local hydrology over the breeding season as well as other individual sparrows. The local hydrology of each 500 meter landscape cell is driven by the 20 year hydrological record (see Hydrology Section).
The figure, at top, represents an example output from SIMSPAR depicting the population estimates for a twenty-year period (1977-1996). This represents a single replicate of the Monte Carlo simulation. The line in the figure represents the overall population trajectory. The triangles mark the population size at the end of the breeding season. The crosses represent the total potential breeding population (pair bonds) and the diamonds represent the number of singing males detected by a "virtual helicopter survey." The virtual helicopter survey follows the same protocol as the field surveys for singing males. These virtual surveys accurately hind-cast the singing males detected during the helicopter surveys conducted in 1982 and 1992 through 1996.