Population Ecology of the Eastern Wild Turkey in Northern Missouri

• Published in: Wildlife monographs no. 130; pp. 3 - 50
• Main Authors: Vangilder, Larry D., Kurzejeski, Eric W.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD The Wildlife Society 01-10-1995; Wildlife Society
• Subjects: Agricultural seasons; Animal nesting; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Fowling; Fundamental and applied biological sciences. Psychology; Harvesting seasons; Hens; Hunting seasons; Mortality; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Population size; Poults; Turkeys; United States; North America; America; Missouri; Vertebrata; Population management; Hunting; Seasonal variation; Mortality; Population dynamics; Aves; Animal conservation; Modeling; Survival; Population density; Meleagris gallopavo
• ISSN: 0084-0173; 1938-5455

The success of eastern wild turkey (Meleagris gallopavo silvestris) restoration programs in the Midwest has led to dramatic increases in occupied range. Habitats with limited forest land, once thought unsuitable for wild turkey, now support densities that exceed 30 birds/ km2 of timber. Turkey population growth has resulted in the liberalization of harvest regulations with corresponding increases in hunter numbers and turkey harvest. As pressures on the wild turkey resource escalate, so does the need for an enhanced understanding of population dynamics. We used radiotelemetry to investigate survival and reproduction of wild turkey hens from 1980 to 1989 in the mixed timber-agricultural region of north-central Missouri. We also used direct recovery rates of banded gobblers to examine spring harvest mortality. Radio-marked hens (n = 327) were monitored annually, ≥5 times/week, to derive estimates of cause-specific mortality, seasonal survival, and reproductive parameters. Band numbers from tagged gobblers (n = 134) were recorded at mandatory turkey check stations to estimate harvest mortality. Seasonal survival rates of hens were variable, with winter rates exhibiting the greatest range (0.625-1.00). Although daily survival rates did not differ among seasons (P = 0.142) according to analysis of variance, a model selection procedure indicated that seasons could not be combined. Cause-specific mortality varied among seasons within years, with predation being the major cause of mortality. Legal fall-harvest mortality averaged 4.4% of radio-marked hens. Illegal kill of hens during the spring gobbler season ranged from 0.0 to 30.0% and averaged 5.2%, exceeding legal fall harvest of hens in some years. During the first year after banding, 17.2% of adult gobblers were harvested during spring hunting season. The nesting rate (measured as the proportion of hens attempting to nest) was consistent and high (≥0.9) across years; however, hen success and nest success showed significant annual variation. hen success differed between adult and subadult hens as did the success of first nests. We observed no difference in the success of renests between age classes of hens. Most poult mortality occurred by 2-weeks posthatch; however, annual estimates varied among years. Poult mortality at 4-weeks posthatch ranged from 0.419 to 0.705. Across years, increasing poult mortality was associated (ρ = 0.75, P = 0.054) with the number of days in June that rainfall exceeded 2.54 cm. We used a stochastic population model to examine the effects of simulated spring harvest on the age structure of males and the effects of fall harvest on population growth. Increasing levels of spring harvest resulted in a decreasing proportion of adult males in the spring population and in the harvest. At a 5% level of fall harvest, population size at year 40 increased in 72% of the simulations. When a 10% level of fall harvest was modeled, population size at year 40 decreased in all simulations. The model was sensitive to changes in hen survival, nest success, and poult mortality. Simulations were run for 40 years with an initial population size of 5,820. Decreases in poult mortality of 10 and 20% resulted in increases in average simulated population size at year 40 of 3,154 and 19,957% (32.54 and 200.57 fold), respectively. The variation we observed in wild turkey survival and reproduction and our population model outputs suggest that harvest strategies can affect population growth and age structure. Fall harvests have the greatest potential to affect population growth. We recommend that state-level estimates of harvest, hunting pressure, reproduction, and survival form the basis for developing and evaluating wild turkey harvest strategies in the Midwest. A conservative approach to spring and fall harvest regulations is recommended if sufficient data to model populations are not available.