Chad P. Lehman

Merriam's Turkey Nest Survival and Factors Affecting Nest Predation by Mammals

Abstract Nest success is an important parameter affecting population fluctuations of wild turkeys (Meleagris gallopavo). Factors influencing mammalian predation on turkey nests are complicated and not well understood. Therefore, we assessed nest hazard risk by testing competing hypotheses of Merriams turkey (M. g. merriami) nest survival in a ponderosa pine (Pinus ponderosa) ecosystem during 2001–2003. We collected nesting information on 83 female Merriams turkeys; annual nest success averaged 50% for adult females (range = 45–59%) and 83% for yearling females (range = 75–100%). Proportional hazard modeling indicated that precipitation increased the hazard of nest mortality. However, estimated hazard of nest predation was lowered when incubating females had greater shrub cover and visual obstruction around nests. Coyotes (Canis latrans) were the primary predator on turkey nests. We hypothesize that precipitation is the best predictor of nest survival for first nests because coyotes use olfaction effectively to find nesting females during wet periods. Temporally, as the nesting season progressed, precipitation declined and vegetation cover increased and coyotes may have more difficulty detecting nests under these conditions later in the nesting period. The interaction of concealment cover with precipitation indicated that nest hazard risk from daily precipitation was reduced with greater shrub cover. Management activities that promote greater shrub cover may partially offset the negative effects of greater precipitation events.

The role of wildfire, prescribed fire, and mountain pine beetle infestations on the population dynamics of black-backed woodpeckers in the black hills, South Dakota.

Wildfire and mountain pine beetle infestations are naturally occurring disturbances in western North American forests. Black-backed woodpeckers (Picoides arcticus) are emblematic of the role these disturbances play in creating wildlife habitat, since they are strongly associated with recently-killed forests. However, management practices aimed at reducing the economic impact of natural disturbances can result in habitat loss for this species. Although black-backed woodpeckers occupy habitats created by wildfire, prescribed fire, and mountain pine beetle infestations, the relative value of these habitats remains unknown. We studied habitat-specific adult and juvenile survival probabilities and reproductive rates between April 2008 and August 2012 in the Black Hills, South Dakota. We estimated habitat-specific adult and juvenile survival probability with Bayesian multi-state models and habitat-specific reproductive success with Bayesian nest survival models. We calculated asymptotic population growth rates from estimated demographic rates with matrix projection models. Adult and juvenile survival and nest success were highest in habitat created by summer wildfire, intermediate in MPB infestations, and lowest in habitat created by fall prescribed fire. Mean posterior distributions of population growth rates indicated growing populations in habitat created by summer wildfire and declining populations in fall prescribed fire and mountain pine beetle infestations. Our finding that population growth rates were positive only in habitat created by summer wildfire underscores the need to maintain early post-wildfire habitat across the landscape. The lower growth rates in fall prescribed fire and MPB infestations may be attributed to differences in predator communities and food resources relative to summer wildfire.

Apparent foraging success reflects habitat quality in an irruptive species, the Black-backed Woodpecker

ABSTRACT Dramatic fluctuations in food resources are a key feature of many habitats, and many species have evolved a movement strategy to exploit food resources that are unpredictable in space and time. The availability of food resources may be a particularly strong determinant of habitat quality for irruptive bird species. We studied the apparent foraging success of Black-backed Woodpeckers (Picoides arcticus), an irruptive species that responds opportunistically to pulsed food resources in burned forests and mountain pine beetle (MPB) infestations. Prior investigations revealed that the highest population growth rates of Black-backed Woodpeckers occurred in habitat created by summer wildfire, with intermediate population growth rates in MPB infestations, and the lowest population growth rates in habitats created by prescribed fire in fall. We tested whether apparent foraging success was associated with known habitat quality in order to assess the potential for food availability to regulate population growth. We counted the number of successfully captured wood-boring beetle larvae and “small” prey on each tree that a Black-backed Woodpecker used for foraging and modeled these counts as a function of habitat, tree diameter, number of years postfire, and tree disturbance category. Total apparent foraging success (the sum of observed captures of wood-boring beetle larvae and small prey per tree) did not vary across habitats, but woodpeckers foraging in habitats created by summer wildfire were expected to capture 2.2 and 2.0 times more wood-boring beetles than woodpeckers foraging in habitats created by fall prescribed fire and MPB infestations, respectively. These results suggest that the availability of food resources may contribute to population regulation in this irruptive species. Furthermore, population growth in irruptive species may be highly sensitive to the availability of preferred food resources. Forests recently burned by summer wildfires provide relatively abundant food resources for Black-backed Woodpeckers and represent high-quality habitat for this species of conservation concern.

A re‐evaluation of a case–control model with contaminated controls for resource selection studies

1. A common sampling design in resource selection studies involves measuring resource attributes at sample units used by an animal and at sample units considered available for use. Few models can estimate the absolute probability of using a sample unit from such data, but such approaches are generally preferred over statistical methods that estimate a relative probability of use. 2. The case-control model that allows for contaminated controls, proposed by Lancaster & Imbens (1996) and Lele (2009), can estimate the absolute probability of using a sample unit from use-availability data. However, numerous misconceptions have likely prevented the widespread application of this model to resource selection studies. We address common misconceptions regarding the case-control model with contaminated controls and demonstrate its ability to estimate the absolute probability of use, prevalence and parameters associated with categorical covariates from use-availability data. 3. We fit the case-control model with contaminated controls to simulated data with varying prevalence (defined as the average probability of use across all sample units) and sample sizes (n1 = 500 used and na = 500 available samples; n1 = 1000 used and na = 1000 available samples). We then applied this model to estimate the probability Ozark hellbenders (Cryptobranchus alleganiensis bishopi) would use a location within a stream as a function of covariates. 4. The case-control model with contaminated controls provided unbiased estimates of all parameters at N = 2000 sample size simulation scenarios, particularly at low prevalence. However, this model produced increasingly variable maximum likelihood estimates of parameters as prevalence increased, particularly at N = 1000 sample size scenarios. We thus recommend at least 500-1000 used samples when fitting the case-control model with contaminated controls to use-availability data. Our application to hellbender data revealed selection for locations with coarse substrate that are close to potential sources of cover. 5. This study unites a disparate literature, addresses and clarifies many commonly held misconceptions and demonstrates that the case-control model with contaminated controls is a viable alternative for estimating the absolute probability of use from use-availability data.

Pre‐incubation movements of female wild turkeys relative to nest initiation in South Dakota

Abstract Nests of radiotransmittered wild turkeys (Meleagris gallopavo) that are destroyed or abandoned prior to incubation are particularly difficult to locate. As a result researchers often report only incubated nests or estimate numbers of nests attempted by localization of movement or other behavioral changes without quantification. We used radiotelemetry to obtain movement data on female wild turkeys during the nesting season (1 Apr-30 Jun) in South Dakota. We collected prelaying (1 April until 14 days before the female initiated incubation) and laying (<14 days before incubation) movement distances from 160 adult female wild turkeys [75 eastern (M. g. silvestris), 19 Rio Grande (M. g. intermedia), and 66 Merriams (M. g. merriami) wild turkeys]. Our objectives were to quantify the relationship between movement behavior and nesting attempts to allow more accurate determination of initiation of nesting for calculation of nest rates, nesting success, and renesting rates. Daily movements of females decreased abruptly when they transitioned from prelaying to laying behaviors. Movements of females that were less than 364.9 m for eastern turkeys, 115.0 m for Rio Grande turkeys, and 331.0 m for Merriams turkeys were indicative of nest initiation. Changes in movements of females can identify nesting wild turkeys and can be used post hoc to identify nests that were abandoned or destroyed prior to incubation if sufficient locations are collected. Following our analysis, we estimated that females had an additional 46 nests (eastern = 15, Rio Grande = 7, and Merriams = 24), which we used in estimating reproduction parameters. Quantitative comparisons of movements between prelaying and laying confirmed a behavioral change of localized movements concurrent with nest initiation in wild turkey females.

Comparison of Microhabitat Conditions at Nest Sites Between Eastern (Meleagris gallopavo silvestris) and Rio Grande Wild Turkeys (M. g. intermedia) in Northeastern South Dakota

Abstract Rio Grande wild turkeys (Meleagris gallopavo intermedia) were trapped in Oklahoma and released in northeastern South Dakota during the early 1970s. Based on wintering counts, this population peaked at over 1000 birds in the mid 1980s, but steadily declined to <200 in 1996. This decline prompted the introduction of eastern wild turkeys (M. g. silvestris), which were indigenous to southeastern South Dakota, as a replacement subspecies. We compared nest site characteristics of translocated eastern wild turkeys with those of established Rio Grande wild turkeys. Over a 2 y period we radio-marked 23 eastern females, and 21 Rio Grande females. Eastern females initiated 45 nests, whereas Rio Grande females initiated 41 nests. Vegetation type selection for nest sites (e.g., woodland, grassland and shrub) did not differ between Rio Grande and eastern wild turkeys (P = 0.96). However, turkey nest sites (subspecies pooled) differed from paired reference sites by having: (1) more nest sites directly under shrubs (P < 0.001) within woodlands and shrublands, (2) more trees within 1 m of the nest bowl (P = 0.001) in woodlands and (3) greater cover above the nest bowl (P = 0.007) within grasslands and shrublands. Frequency of vegetation types selected by female wild turkeys of both subspecies as nest sites differed (P = 0.001) from the frequency of vegetation types randomly sampled. Although shrub vegetation types were least available, females selected shrub vegetation types (primarily western snowberry [Symphoricarpos occidentalis]) for the majority (53%) of nest initiations. Other nests were divided between woodlands (27%) and grasslands (20%). Nest success was not correlated with vegetation type.

Adult Pronghorn (Antilocapra americana) Survival and Cause-specific Mortality in Custer State Park, S.D

Abstract Although understanding natural mortality rates of ungulate populations is essential for effective management, published data on adult survival from unharvested pronghorn (Antilocapra americana) populations in the Northern Great Plains is limited. We estimated seasonal adult survival rates and cause-specific mortality of an unharvested pronghorn population in Custer State Park, S.D. We assessed the relative importance of sex, age, year, and season in explaining pronghorn survival rates using an information-theoretic approach. We captured and radio-collared 26 male and 24 female adult pronghorn from fall 2005 through spring 2008. We observed higher predation rates and lower survival of adult pronghorn in CSP compared to other populations in the region, but similar to the pronghorn population in Yellowstone National Park. We documented 23 deaths (10 females, 13 males) of the 50 radio-collared pronghorn from Nov. 2005–Nov. 2008. Predation by mountain lions (Puma concolor) and coyotes (Canis latrans) accounted for 69.5% of all mortalities. The season model received the greatest support although there also was strong support for the season × sex model. Seasonal survival for males and females was >0.90 for the winter-grouping and breeding seasons but fell to 0.791(95% CI 0.644–0.887) and 0.837 (95% CI 0.706–0.916) for females and males, respectively, during the small group – parturition season. A dense predator population, as well as a higher vulnerability to predation when pronghorn are solitary or in small groups, may explain the lower survival during these time periods. If population estimates fall below management goals, management actions aimed at reducing predator cover may be beneficial to adult pronghorn. Managers of pronghorn populations near forested and rugged areas and that are sympatric with dense predator populations should consider adult survival may be lower than observed in Great Plains populations.

Extended Duration of Parturition Season in North American Elk (Cervus Elaphus)

Abstract The timing of births in ungulates has significant implications for juvenile survival and population growth. For North American elk (Cervus elaphus), typical parturition season ranges from late May to early Jun., and juveniles born outside of this peak characteristically exhibit lowered survival. We observed abnormally long parturition seasons in free-ranging elk populations in Missouri and South Dakota during 2012. Both populations exhibited late births; the last known births occurred on 26 Sep. in Missouri and 4 Sep. in South Dakota. Duration of parturition season was 112 and 119 d in Missouri and South Dakota, respectively. In Missouri, late births likely resulted from breeding by both yearling females and males. Late parturition in South Dakota may be caused by extended estrous cycles of elk that occurred on high quality range where few adult males were located.

OBSERVATION OF DYSTOCIA IN WILD ELK

ABSTRACT. On the basis of reports in the literature, incidence of dystocia in wild elk (Cervus elaphus) across the west is rare. In 2011, one of 34 (3%) pregnant cow elk in our study experienced dystocia during birth. Our visual observations indicated that it took approximately 4 days for a radio-collared cow elk to succumb to dystocia in our study. Little is known about dystocia in wild elk populations, and our observation provides some insight about fetal malpresentations.

Ground Roost Resource Selection for Merriam's Wild Turkeys

Abstract Concealment cover is important for ground-roosting wild turkey (Meleagris gallopavo) poults immediately following hatch during the vulnerable, preflight stage. We compared concealment cover resources selected at ground roosts to those of nest sites and available resources for Merriams turkeys (Meleagris gallopavo merriami) in the Black Hills of South Dakota, USA. Females with preflight poults selected ground roosts that were similar in structure to nest sites. Ground roosts and nests were greater in visual obstruction (unit odds ratios ≥1.19) than random sites. However, ground roosts were closer to meadow–forest edges than either nests or random sites (unit odds ratios ≤0.98). Structure at ground roosts may provide visual protection from predators, and management for shrub vegetation or woody debris along meadow–pine forest ecotones will provide cover for Merriams turkey broods.