The Impacts of Fire and Climate Change on Wild Turkeys
It is spring wild turkey (Meleagris gallopavo) season throughout much of Canada and the United States. Hunters throughout the continent live for this time of year, with its sunrise glows, dewy morning fields, fragrant sunny days, and forests screaming with the gobbles of male turkeys.
Some recent research has given us more insight into turkey habitat preferences, use, and what we might expect for the future of wild turkey range in the context of climate change and land management. In particular, I want to review three studies that together help us piece together wild turkey habitat use from localized to regional to population scales. They also tell us about how prescribed burns, land use, and climate change impacts wild turkey habitat selection.
For more on this topic and the research covered here, check out Episode 19 – All Things Wild Turkey of the Hunt To Eat Show.
Wild Turkey History
Many hunters are familiar with the history of wild turkeys in North America. The unfortunate abbreviated version follows some of the same main plot points as many other wildlife species on this continent.
At some point around the early 1900s, turkey populations had been reduced to about 30,000 birds across the continent. That decline was due primarily, as with the decline of many other species across North America, to overhunting and habitat degradation and destruction. Some exceptional conservation efforts went into restoring wild turkey populations through capture and release initiatives across the U.S. and Canada. Today we have an estimated 7,000,000 turkeys across five subspecies throughout the continent.
Turkeys are certainly one of the best conservation success stories in North America.
Wild turkeys are a tough and adaptable bird. They live across a range of environments, habitats, and land cover types. Typically, we think of wild turkey range as being limited by weather. Historically, wild turkeys were limited to roughly 45 degrees of latitude. They now occur above 50 degrees latitude and researchers continue to explore factors that influence turkey range expansion.
Generally speaking, wild turkey range is limited by snow accumulation, which restricts their winter access to food, resulting in lower winter survival. Typically, they are limited by snow depths that exceed 30 cm for more than 10 days. So, they can withstand periods of snow but not for prolonged lengths of time. And especially in cases where you have deep snow for long periods of time and lower temperatures, those compound to affect turkey survival.
Understanding climate and landscape thresholds influenced where conservationists focused turkey conservation initiatives over the latter half of the 20th century. For example, before turkey restoration efforts in the 1960s, biologists didn’t think turkeys would become established in the Upper Midwest of the United States because of the severity of winter weather and the lack of forest cover in what was predominantly an agriculturally dominated landscape. Initial reintroduction efforts prioritized areas that were mostly forested. Once conservation efforts were successful in some of those more high priority areas, biologists moved on to areas that were less optimal in terms of habitat and climate.
Wild Turkeys Use Burned Habitats Differently
The first study was led by researchers at the University of Illinois and the Illinois Department of Natural Resources and published in a paper titled Pyrodiversity Matters: Wild Turkey Habitat Selection in a Fire Managed Landscape.
Wild turkeys thrive in forests with a diverse understory structure and this type of habitat can be created using prescribed fire regimes. The researchers asked two questions. First, does prescribed fire influence habitat selection among wild turkey hens? And second, how does hen habitat selection respond to differing burn regimes?
The research team monitored the habitat use of 47 hens in south-central Illinois using GPS trackers. They found that hens did not use burned forests more than non-burned forests. However, the hens used burned forest areas differently throughout the breeding season.
Results showed that the length of time since an area was burned and the burn frequency influenced where and when hens spent time during the reproductive season. During the egg laying and incubation periods, hens used areas that had gone through at least one growing season more than they used areas burned that current year. Hens were looking for understory growth as cover and protection. Areas that had at least one year of growth provided more cover and concealment for nesting hens and young. In fact, no hens in the study nested within recently burned forests. While hens didn’t nest in burned areas, they did use areas that had been recently burned to access fresh forage during the incubation period. Then, during the post-nesting time, the study found that hens used a greater proportion of areas with higher burn frequencies.
The study points broadly to the importance of what is referred to as “pyrodiverse landscapes.”
Hens used the landscape mosaic created by prescribed burn regimes differently during their reproductive season and out of their reproductive season. What this study highlights is the importance of considering both the habitat areas used by wildlife and the different ways wildlife use habitat throughout the year. Wildlife managers need to take both spatial and temporal considerations into account when evaluating the effects of land management on wildlife.
In terms of overall management recommendations, here’s what the authors have to say:
“For those interested in managing a forested landscape for wild turkeys, we recommend 1) develop burn prescriptions that produce a blend of time since burn and burn frequencies, and 2) retain some non-burn forest which may be used for nesting, as refuge by turkeys and other wildlife during burning events, and as places where turkeys can find forage items that are not burn tolerant.”
This study looked at the kind of habitat mosaics turkey use on a finer scale. What happens when we consider wild turkey habitat use at larger, regional scales?
Wild Turkeys Need Open and Forested Land
The second study was led by researchers out of the Wisconsin Department of Natural Resources and the Department of Forest and Wildlife Ecology at the University of Wisconsin-Madison and published in a paper called Gobbling Across Landscapes: Eastern Wild Turkey Distribution and Occupancy–Habitat Associations.
The study looked at the influences of habitat characteristics (e.g., winter snowfall, annual cropland rotations) on where turkeys live in two populations across Wisconsin. The first area was the more heavily forested northern regions of Wisconsin and the second was in agriculturally dominated southeast Wisconsin.
This study used a method called gobbling call-count surveys to evaluate turkey distribution, population abundance, and phenology of gobbling. The methods involved travelling along a set route and stopping at multiple listening locations to listen for gobbles.
The researchers conducted 1,815 surveys across 157 gobbling call-count routes in northern Wisconsin, and 1,235 surveys on 103 routes in southeast Wisconsin.
Here’s what they found:
“The environmental constraints of turkey occupancy varied across the latitudinal gradient of the state with open land cover, snow, and row crops being relatively more important in northern Wisconsin, while the effect of hardwood forest cover was stronger in southeastern Wisconsin.”
In other words, in northern Wisconsin in more heavily forested areas, turkeys benefitted from open cover types. Conversely, in southeastern Wisconsin that’s dominated by agricultural areas, turkeys benefitted from aggregations of hardwood forests. Turkeys in both areas benefitted from a mosaic of habitat types that provide turkeys with the areas they need for food, cover, and strutting behaviour.
Impacts of Climate on Wild Turkey Range
From individually burned areas within one region to comparisons between two larger regions dominated by different land-use patterns, this brings us to factors that affect turkeys at a population level. The last study was led by researchers at the University of Laval in Quebec and published in a paper called Extreme Climate Events Limit Northern Range Expansion of Wild Turkeys.
Climate change has caused many animal populations to shift their ranges as optimal habitat conditions change. Globally, more than 1,300 species have expanded their ranges towards the poles by 17 km per decade. Environmental changes especially affect populations at the edge of their geographic ranges and researchers have found that extreme weather events predict species distribution more than average climate conditions. As we know, the frequency and severity of extreme weather events are changing due to climate change.
As the climate warms, some models predict a decline in the frequency of extreme snow events while others predict they will remain stable. Broadly speaking, we expect climate change to lead to milder winters and the authors of this study note that warmer temperatures and lower rainfall can buffer the effect of snowfall and predicted that this might allow wild turkey populations to expand further north.
The study examined the impacts of extreme weather events on wild turkeys. It also looked at projections of future climate conditions from the Intergovernmental Panel on Climate Change (IPCC) and made predictions about the population growth and likelihood of further northward expansion of wild turkeys.
For this study, the researchers looked at three populations of turkeys in Quebec, Canada that span different latitudes but that all generally represented the northeastern range limit of wild turkeys. Going back to the impacts of snow, the northernmost area receives more than twice the snowfall of the southernmost area. The southernmost population of the three was established around 1976, while the midrange and northernmost population were only established in 1992 and 1997, respectively.
The researchers captured 344 wild turkeys over the span of three years and fitted 185 females with either a radio transmitter or a GPS tracker. The researchers tracked movements, reproduction, and survival of birds in the three populations to estimate whether the populations were self-sustaining or relied on immigration and movement between populations.
Biological theory says that when species move to new areas they naturally prioritize reproduction over survival during initial phases of population establishment. In other words, species tend to put more energy into reproducing and putting a lot of offspring on the landscape over their own adult survival. This isn’t a conscious decision, it’s just something that biology leads species to do to persist at a population level.
This study observed this dynamic, too. It found that for turkeys in the southern population – where the population is more firmly established and near its saturation point – poult production was lower and adult survival higher. As they moved north, this started to shift. Turkeys in the northern population had a higher rate of poult production but lower adult survival, meaning that the population dynamics in the north suggested those populations are still expanding.
Future Wild Turkey Range under Climate Change
The last study discussed above noted that extreme weather events are likely to impact wild turkeys more than average climate conditions. Since snow depth is the main factor affecting wild turkey adult survival and population growth rate, it follows that less snowfall and warmer temperatures are the key to wild turkeys successfully establishing viable northern populations. However, while wild turkey range is generally limited by the 30 cm snow cover benchmark, we also need to understand the likely frequency and severity of extreme weather events.
However, with all of this in mind, what did they find overall? The researchers found that a combination of rain, temperature, and extreme snow events means that the northern population would not persist on its own without immigration from the other populations. Here’s what they report about their results:
“Despite that more infrequent snowfall and mild cold spells will arise in the future, our population projections suggest that wild turkeys are unlikely to establish further north without immigration. Whether southern populations will be able to sustain a flow of emigrants is an open question. In most cases, even if the frequency of harsh winter snow events and long spells of cold temperature is projected to decrease, it will remain above the threshold preventing the persistence of wild turkey populations.”
The authors conclude that the northernmost population is actually projected to decline by 2100. Their population projections show that each time an event of immigration from a southern population occurs throughout the next century, the northernmost population will decline dramatically, being almost extinct after 10 years in most cases.
These studies give us some insight into how wild turkeys might respond to changing habitat conditions due to land management decisions and climate change.
What all of these studies mean for management and conservation is that managers need to pay attention to a range of habitat features and factors to make more localized and adaptive decisions about wild turkey conservation.
We can’t just look at large landscape level factors because we see that turkeys in different areas – areas dominated by different land cover types and weather – need different kinds of habitat features to persist. The different needs of turkeys throughout their range necessitates different approaches to management.
While wild turkey populations are at sustainable levels across the continent now and have certainly rebounded extraordinarily from declines in the early 1900s, we do still need to pay attention to wild turkey conservation and make sure that we make decisions that protect their conservation.
Ultimately, what we urgently need, for all species and habitats, is more effective climate change policy and action. It will be increasingly difficult to predict changes in wildlife populations and implement actions for their conservation as climate change leads to more dramatic weather events and habitat changes.
For those of us who have a deep affection for wild turkeys and all they represent, staying focused on actively conserving the species and its habitat will help keep them around for a future filled with spring hunting seasons.