Heading South for the Winter: A Duck’s Travel Guide on When to Hit the Road & Where to Stop Along the Way
With dawn breaking to the southeast, the sound of wings cutting through the air began to fill the sky. The soft chuckles of a duck call greeted a pair of mallards as they dipped down towards decoys floating with the wind. Then, at the legal hour, a shotgun blast christened the start of the 2020 regular duck season in Michigan’s southern zone. As I walked to retrieve the bird, my thoughts drifted, as they often do, to all the factors that came together to make this moment possible.
Michigan is situated in the center of the migratory funnel that is the Great Lakes Region. Offering everything from beaver ponds in the Upper Peninsula, to the open waters of the Great Lakes, this state is truly a paradise for waterfowl and recreationalists alike. My graduate research focused on seven Managed Waterfowl Hunt Areas (MWHAs) operated by the Michigan Department of Natural Resources (MDNR) and the Shiawassee National Wildlife Refuge (NWR). These areas are located throughout Michigan’s Lower Peninsula and have garnered international recognition for their role as key staging areas for autumn migrating waterfowl. A staging area is characterized as a perennially available wetland complex that provides an abundance of available food and space for waterfowl to gather before making migratory movements. Additionally, staging areas are also generally associated with recreational opportunity and my study sites are no exception. Given the immense socio-economic value of waterfowl, there is a need to continuously reevaluate the regional and local conditions that influence use by the birds and recreationalists alike.
As such, the goal of my research was to observe trends in waterfowl migratory movements, expand upon our understanding of habitat selection on a local scale, and characterize how hunter use and success can be impacted by local conditions. To achieve this, I dove into archived waterfowl abundance and harvest datasets maintained by area managers and monitored fine scale waterfowl spatial use across two migratory periods using a novel method in camera trapping.
Waterfowl migration is driven by a combination of environmental and internal cues and understanding how these cues interact with each other has major implications for both management and recreation. Research has shown that the initiation of migratory behavior in birds (known by the German word “Zugunruhe”) is triggered in the fall by day length, but is further stimulated by environmental conditions. Additional work found evidence for migration occurring later in the season, potentially due to climate change mitigating the prevalence of the severe winter weather conditions (i.e., freezing temperatures and snow) that serve as a catalyst for migratory movements. Once waterfowl arrive in an area, the condition of wetlands directly affects how they distribute themselves across the landscape. Because each species within the broader waterfowl group has slightly different ecological needs, managers work to provide a suite of habitat conditions through intense active management. This management consists of promoting the growth of desirable plant species through water level manipulation and planting, minimizing the spread of exotic invasive plant species, and mitigating excessive human disturbance associated with recreation.
I analyzed nearly 30 years of waterfowl abundance data against various climate, weather, and hydrology measures. These analyses suggested that the timing of bird movement through the state is trending towards later in the year (i.e., timing of peak abundance observations). However, this trend is not uniform across species or area. With regard to the number of birds that move through the areas on an annual basis, my analyses suggest that the total number of ducks using them during a core October — mid-December migratory period is declining. These total “duck use days” coarsely track estimates of Michigan’s breeding mallard populations and could be evidence of an underlying regional phenomenon. The combination of these analyses reaffirms the need for landscape level planning to manage for a suite of available habitats on a regional scale, as this would help ensure the prosperity of waterfowl and the recreation associated with them in the state.
In addition to regional migratory movements, understanding local habitat selection is paramount. To provide insights on this, I maintained 80 camera traps from August to January in the 2018 and 2019 autumn migratory periods. During this time, my cameras took more than a million photos and documented approximately 250,000 ducks. While commonly employed in natural resource related work, to my knowledge, this work is the first time since the 1960s that cameras were used as the primary tool in a formal study of waterfowl wetland use. Having come a long way in the past half century, today’s units offered a way to continuously monitor species-specific waterfowl use across large wetland complexes, in response to management regimes and other local conditions without disturbing birds or the hunters pursuing them. I observed spatial and temporal shifts in duck use, primarily as a function of human disturbance. A more uniform distribution of duck use was observed prior to the beginning of hunting seasons but shifted towards high relative abundances in areas closed to hunting during the day and increasing nocturnal use of hunted areas as the season progressed.
Hunter success is largely a function of those aforementioned regional movements and local habitat selection. Despite variable timing of peak abundances and large shifts away from use of habitats open to hunting during daylight hours, duck harvest in these areas remains consistent with historical norms. Notably, these areas routinely account for approximately 10% of the state’s estimated annual duck harvest totals (MDNR and US Fish and Wildlife Service unpublished data). This was observed in harvest data dating back to the 1990s, showing a level of consistency achievable only through active and intensive wetland management.
Waterfowl have immense socioeconomic value. This is likely why they are among the most studied avian groups and the only one to broadly exhibit net population increases since the 1970s. However, numerous factors (e.g., wetland loss and degradation, land use change, etc.) bring into question what the future of waterfowl conservation will look like. As such, there is a need to manage for both the prosperity of the group as well as the recreation associated with them. My hope is that this work will serve as a tool to help inform future management decisions on important staging areas in Michigan. As I take steps to finalize my research, I think how fortunate I am to have a graduate project that afforded a unique opportunity to learn about the many aspects of waterfowl biology that contribute to interactions, like the one I enjoyed on opening day, which may only last a moment.
ALL PHOTOS: TREY MCCLINTON
Trey McClinton is a Master’s student co-advised by Dr. Dan Hayes and Dr. Dave Luukkonen. His research interests include avian ecology and habitat management, with a focus on waterfowl and wetlands. He can be reached at firstname.lastname@example.org.