Seasonal survival and harvest rates of ruffed grouse in central Maine, USA

Individual survival is a fundamental component of population dynamics, and knowledge of factors that influence survival is important for understanding fluctuations that occur within populations. Ruffed grouse (Bonasa umbellus) is considered generally abundant in Maine, but along their southern range margin and in parts of New England their populations have experienced long-term declines. Our objectives for this study were to estimate rates of survival and harvest of radio-marked ruffed grouse in central Maine and evaluate sources of temporal (annual, monthly, seasonal, and weekly), spatial, and individual (age, sex, and body condition) variation on survival. We estimated a cumulative harvest rate of 0.134 ± 0.05 (SE), 0.158 ± 0.002, and 0.079 ± 0.002 for 2014, 2015 and 2016 respectively. Harvest was greatest during the month of October in all years, with slightly higher December harvest during 2015 compared to 2014 and 2016. Weekly survival probabilities of radio-marked ruffed grouse indicated lower survival of juveniles (< 1 year of age) compared to adults (>1 year of age), and both age classes experienced lowest survival during winter (January-March), and highest survival during summer (June-September). The cumulative annual survival of juveniles from October 1 to September 30 was 0.16 ± 0.03, and the cumulative annual survival of adults was 0.32 ± 0.04. Overall, we found that adult ruffed grouse had greater survival than juveniles and monthly harvest rates were highest in October and lower in November and December for all years.

Faculty Mentor: Erik Blomberg

Co-authors: Joelle Mangelinckx