A model of Gray Partridge (Perdix perdix) population dynamics in North Dakota.

Abstract

POTTS (1986) developed a deterministic key-factor-analysis model of gray partridge (Perdix perdix) population dynamics in southern England. The model is composed of 5 k-factors including: clutch mortality, hen mortality during incubation, chick mortality, hunting mortality, and winter mortality. I modified this model to simulate populations in North Dakota. The North Dakota model accounted for higher per clutch production, higher nest mortality rates, and greater winter mortality. The results show that predator control during nesting and increased nesting cover would contribute to increases in population density. Chick mortality rate was not a significant mortality factor. At linear nesting cover levels comparable to those found in North Dakota (2 km/km²) the model predicted spring populations of 6 partridge/km² with predator control and 2 partridge/ km² without predator control. For levels of nesting cover similar to the best found in North America (4 km/km²), spring populations were predicted to be 12 and 3 partridge/km², with and without predator control, respectively. Comparisons of model predictions to data collected in North Dakota suggest that the model has predictive value for age ratios (P = 0.04), but is weak in predicting autumn populations (P = 0.13). Although chick mortality was a good predictor for age ratios (P < 0.001) and autumn populations (P < 0.001) in the model, prediction of observed age ratios (P = 0.72) and autumn populations (P = 0.16) from chick mortality was low. These data suggest that chick mortality is not important for predicting yearly increases in population (P = 0.49), thereby supporting clutch mortality as the most important production factor.