Mallard habitat selection during the non-breeding season
Tennessee provides a novel system to study waterfowl behavior, movements, and habitat selection due to the number and acreage of waterfowl sanctuary in the western part of the state. In addition, mallard harvest seems to be declining in the state despite record breeding population size, thus indicating a need for resource agencies to understand if habitat or population management may be improved. State-of-the-art GPS tracking technology now allows researchers to monitor avian movements and habitat selection at unprecedented spatiotemporal granularity which will provide more complete portrayals of life-history strategies during non-breeding periods.
The Tennessee Wildlife Resources Agency (TWRA) and U.S. Fish and Wildlife Service (USFWS) will use our results as the basis for land acquisition, season establishments, and habitat management decisions in Tennessee. Further, we expect our results will generalize geographically to most wintering habitats with similar hunting pressure and acreages of refugia.
Waterfowl response to disturbance on sanctuary areas
Historically, it has been difficult to understand and quantify the impact anthropogenic disturbance has on waterfowl populations. Current assumptions associated with disturbance is inferred from reported hunter harvest within each state. Due to this information gap, there is a need to greatly expand upon our understanding of how non-lethal disturbance may impact waterfowl at a local and regional scale.
This study aims to identify how mallards respond to different types of disturbances on sanctuaries and how this disturbance influences hunter opportunity in the adjacent areas. There is also a need to understand what spatial and temporal factors such as water availability across the landscape and hunting pressure influence mallard response to systematic disturbance. Filling these information gaps will inform managers on whether they should restrict activities within a sanctuary or open sanctuaries to human activity on some level.
Using machine learning to identify landcover and water
Resource selection of an animal depends on the abundance and availability of a resource. West Tennessee contains a considerable amount of private and public wetlands managed specifically for wintering mallards and other ducks; however, the number and areal acreage of privately managed wetlands is unknown but likely contributes significantly to overall landscape energetic carrying capacity for wintering ducks in the region. Furthermore, winter flooding increases the availability of natural wetlands (i.e., non-managed).
Based on historical research, we expect mallards and other dabbling ducks to diversify their diets and exploit naturally flooded areas, especially during late winter when planted foods begin to deplete beyond a certain threshold. However, no one has predicted the spatiotemporal variation in flooding in west Tennessee or in the Mississippi Alluvial Valley. We are using a combination of aerial surveillance, ground vegetation surveys, remote sensing, and machine learning techniques to predict areal coverage of managed wetlands and natural flooding in west Tennessee. We will use landcover and flooding layers to explore variation in movement and habitat use of mallards during winter.
Landscape ecology of mallards during their annual cycle
Effective conservation of highly mobile species, such as waterfowl, requires a thorough understanding of proximate and ultimate cues governing habitat use at different stages across the annual life cycle. We are investigating the non-breeding ecology (fall-spring migration) of mallards wintering in the Mississippi Alluvial Valley. Using tools such as novel aerial surveillance, remote sensing, and GPS transmitter technology to examine effects of hunting pressure, surface water inundation (i.e., backwater flooding), landcover energetics, and protected area conservation relative to habitat use and survival.
The Tennessee Wildlife Resources Agency and U.S. Fish and Wildlife Service will benefit from an understanding of movement patterns that enhance survival during winter. Likewise, proximate factors that result in different spring migration strategies (e.g., timing, stopover duration) may reveal critical spring-migration habitats, opportunities to refine habitat management (e.g., drawdown timing), and possible cross-seasonal fitness consequences during this understudied portion of the waterfowl annual cycle.
Forage availability for wintering waterfowl
Despite modifications to historic wetland cover and changes in land use, waterfowl such as mallards have quickly adapted to agriculturally dominated landscapes and readily exploit dry and flooded agricultural fields. Mallards still require natural foods such as moist-soil seeds, tubers, hard mast, and aquatic invertebrates; however, agricultural seeds generally contain more true metabolizable energy (TME) than natural foods. Forage availability and energetic quality immediately prior to mallard spring migration is arguably one of the key factors influencing migration success. Therefore, if resources are exploited early in winter, prior to spring migration, food shortages may have subsequent effects on mallard populations.
Our objective is to estimate biomass, energetic use-days, and depletion of flooded unharvested corn for wintering waterfowl in western Tennessee. Our results will provide natural resource managers with an estimate of food biomass on the landscape and assist in determining whether the available amount of energy supplied from management practices is sufficient for wintering waterfowl populations preparing for their spring migration.
Wild Turkey Brood Habitat Use
Resources are located heterogeneously across the landscape, forcing animals to make behavioral tradeoffs and select for patches that best accommodate their energetic and thermoregulatory needs while balancing predation risk. These behavioral tradeoffs manifest as shifts in habitat selection wherein animals change their spatiotemporal use of habitats to meet current and future needs. While some aspects of habitat selection (nest-site, roost-site, etc.) have been extensively studied in wild turkeys (Meleagris gallopavo), brood habitat selection is one of the least understood aspects of wild turkey reproductive ecology. Despite many populations having rebounded across the country in recent decades following reintroduction and new introduction efforts, recent research indicates that turkey populations across the southeastern United States are experiencing declines in productivity and recruitment, as evidenced by decreasing poult-to-hen ratios. These declines in poult-to-hen ratios raise concerns about the availability and composition of quality brooding habitat.
To better understand fine-scale factors influencing brood habitat selection, we measuring arthropod biomass as a measure of forage availability, air temperature as a measure of thermoregulatory stress, and vegetation characteristics as a measure of cover at known locations of brooding and non-brooding female eastern wild turkeys in Georgia and Louisiana. Additionally, we are investigating habitat selection of broods at the landscape scale as broods age. Our objective is to help wildlife managers in identifying and managing for habitat characteristics desirable to turkey broods, especially in pine-dominated systems of the southeastern United States.
White-tailed Deer Population Monitoring
Monitoring abundance over time is a critical first step for managing wildlife populations. However, a tradeoff exists between the cost of collecting monitoring data and the precision of the estimates provided by the data collected. We are collaborating with Tennessee Wildlife Resources Agency (TWRA) to develop tools to improve monitoring white-tailed deer populations across Tennessee.
We will develop an integrated population model (IPM) that capitalizes on existing harvest data that are commonly collected in exploited populations to estimate abundance of deer annually. Further, we will evaluate tradeoffs between the amount and type of monitoring data included and the precisions of estimates from the IPM using structured decision making (SDM). This will provide guidance on sampling effort to meet the objectives for monitoring deer in Tennessee.