Factors affecting long-term counts of drumming ruffed grouse in Missouri [abstract]
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Ruffed grouse were nearly extirpated in Missouri during the early 1900's because of habitat loss but several populations were re-established by reintroductions. The number of drumming-male grouse has been surveyed on the Thomas S. Baskett Wildlife Area since their reintroduction in 1962. We used this 44-year time series to investigate factors regulating grouse populations and the success of reintroduction efforts. We used an information theoretic approach to investigate support for several hypotheses, and combinations of them, concerning factors affecting the number of drumming males. We hypothesized that grouse numbers were: 1) positively affected by the amount of early successional forest habitat; 2) positively related to mast production in the previous year; 3) negatively related to the severity of the previous winter; and 4) positively related to favorable weather the during the previous nesting and brood rearing period. We digitized a series of aerial photos from 1962-2004 and interpolated values for years between photos to estimate the amount of early successional habitat. We used weather data from the Columbia Regional Airport 5-km north of the study area. We used Poisson regression models to relate the number of drumming male grouse to explanatory variables representing the above hypotheses. We evaluated support for our hypotheses using AIC weights and also evaluated the prediction accuracy of our models. Preliminary analyses suggest the amount of early successional habitat had the greatest effect on grouse numbers. Our research will assist managers considering population management and the reintroduction of grouse in Missouri.