Factors Influencing Survival, Productivity, and Population Growth of Eastern Wild Turkeys in Northeastern South Dakota

Abstract

The population of eastern wild turkeys in northeastern South Dakota appeared to be expanding soon after reintroduction in the 1990s, however, recent harvest trends suggest declining abundance in the region. Spring turkey hunting expenditures are projected to be around $6.5 million in South Dakota, with about $3 million of those expenditures occurring within the northeastern prairie region. However, the number of birds harvested during the spring prairie firearm season has been declining since 2010. Due to concerns about a declining population, the autumn hunting season was closed in 2014. The cause of the apparent decline is unclear. Updated demographic information is needed to assess the status of the population of wild turkeys in northeastern South Dakota and to determine the most effective management strategies for increasing abundance across the region. I captured and radio-marked 80 eastern wild turkey hens (43 adult and 37 yearling) in Grant County, South Dakota during the winter of 2017, and I radio-marked an additional 41 yearling hens during the winter of 2018. I monitored radio-marked hens for survival and productivity from February 2017 to April 2019. I used Bayesian methods to model hen survival, nesting rate, nest survival, re-nesting rate, clutch size, hatchability, and poult survival as a function of covariates. I used estimates of productivity to calculate the fecundity rate for both age-classes of wild turkeys. I incorporated estimates of hen survival and fecundity into a matrix projection model, and I performed perturbation analyses and conducted a life-stage simulation analysis (LSA) to assess the impact of each demographic parameter on population growth. Annual survival for both age-classes of wild turkey hens was about 62.5%. The probability a hen would initiate a nest was 77.1% and the probability a nest would survive the 28-day incubation period was 49.3%. The probability a hen would initiate a second nest after a failed first nest attempt was 59.6% for adult hens and 25.1% for yearling hens. The mean clutch size for all nests was 10 eggs and the probability an egg would hatch was 87.1%. The probability a poult survived the 28-day post-hatch interval was 35.5% for poults reared by adult hens and 19.7% for poults reared by yearling hens. The population of eastern wild turkeys in northeastern South Dakota is currently stable-to-growing (λ = 1.107), and population growth is most greatly affected by changes in hen survival. Management activities should focus on improving hen survival by reducing the top two sources of mortality-mammalian predation and haying by agricultural equipment. Enhancing the quality of herbaceous and early successional habitats could reduce hen risk of mortality while conducting nesting and brood-rearing activities. Additionally, increased availability of suitable nesting habitat on the landscape could mean fewer hens will resort to nesting in alfalfa hayfields, where nest failure is certain and hens are at risk of mortality due to haying. Improving eastern wild turkey h...

Factors influencing rate of decline in a Merriam's wild turkey population

“…Moreover, a stable or growing population can only occur if yearling and adult survival increases. Our results support a body of evidence that targeting adult female survival can strongly influence population growth rates (Wakeling 1991, Vangilder and Kurzejeski 1995, Rolley et al 1998, Alpizar‐Jara et al 2001, Tyl 2019). It has been recommended that fall harvests <10% are conservative and will not cause population declines, but these populations are characterized as having higher survival rates (≥56%) with greater reproductive output and can compensate for some female mortality from a fall harvest (Vangilder and Kurzejeski 1995, Alpizar‐Jara et al 2001, McGhee et al 2008).…”

“…For populations of wild turkeys, vital rates of interest typically focus on the female segment of the population and include estimates of adult and yearling survival, nesting rate, nest survival, re‐nesting rate, clutch size, hatchability, and poult survival (Rumble et al 2003, Pollentier et al 2014 a ). Population growth rates of wild turkeys are sensitive to changes in adult female survival (Suchy et al 1983, Wakeling 1991, Vangilder and Kurzejeski 1995, Alpizar‐Jara et al 2001, Tyl 2019). Wild turkey populations may have negative population growth if fall harvests decrease female survival (Vangilder and Kurzejeski 1995, Alpizar‐Jara et al 2001).…”