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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

© Matt Lechmaier
Researchers studied gobbler survival near Black River Falls.

© Matt Lechmaier

April 2007

Signals from the pastures and the ridge tops

Two years of tracking the wanderings of wild turkeys shows the mix of field and forest habit at that gobblers prefer.

Matt Lechmaier

By 2:30 on a January afternoon, we have been sitting in an unheated blind for eight hours scanning the same snowy hillside west of Black River Falls for signs of wild turkeys. Fresh tracks in the snow and personal observation from a nearby landowner confirmed that turkeys had roosted on the ridge above us during the previous night. Finally we hear a series of clucks and purrs from behind the hunting blind and a bachelor group of ten toms makes its way to feed in the harvested soybean field in plain view next to us.

Though nearly 200,000 turkey hunters won't take to the woods until April, we are enduring the winter weather to gather information about turkey behavior and ecology that may interest those hunters and other wildlife watchers. We are examining what factors help wild turkeys survive, thrive and extend their range here in western Wisconsin.

For this wildlife management project, we have spent from January until June during the past two years conducting fieldwork. The majority of our time during January and February is spent trying to catch turkeys using rocket nets.

We begin by searching for signs of turkeys in harvested agricultural fields. During winter, they often feed on waste grain near their roosts in adjacent wooded areas. When we find an area where turkeys are feeding regularly, we set out our trapping equipment and wait in a hunting blind nearby until the turkeys return.

During the winter, the hens remain in family groups with last year's poults, while jakes and the toms we are targeting will flock together in bachelor groups. The amount of time it takes to catch any particular group varies and may range from a couple of hours to several days.

Occasionally we will watch as part of a flock feeds on or near our hunting blind while the rest of the turkeys are nearby preening, foraging, displaying, sleeping, chasing each other or exhibiting many other entertaining behaviors. Sometimes a member of the flock detects movement across the field, lets out a high-pitched "putt" and the group disappears into the woods long before we see anything. Hunters will recognize this same distinctive "putt" call as the grace note that has marked the end of countless hunts. It's a warning to all other birds in the area that the turkey has seen something out of the ordinary.

Turkeys rely on keen eyesight to detect predators, and multiple sets of eyes continually scanning the landscape are an effective way of keeping the flock safe.

If we are quiet and lucky, the turkeys won't detect us. When all or most of the flock is feeding on the corn pile, we detonate the charges in three small rockets and launch them over the turkeys' heads. These rockets are mounted on top of a box containing a net that measures about 30 ft. by 40 ft. The leading edge of the net is attached to the rockets while the back edge is anchored by cinder blocks. The net deploys in an instant, and covers the turkeys before they can react to the sound of the detonation. It is so fast, in fact, that we use cracked corn as bait to keep the turkeys from inhaling and choking on whole corn kernels as the rockets shoot by overhead. During the past two winters, we have caught 151 toms (adult males) and 25 jakes (juvenile males) without any mortality during capture.

Capturing and handling turkeys is the most exciting part of this fieldwork. At first I was concerned that the birds would become hypothermic while resting under the net trapped against the snow, but in fact the opposite is true. We take each turkey out from under the net individually, using one arm to hold their wings in and the other to restrain their legs. Their legs feel hot to the touch and are warm enough to keep our bare hands comfortable. Some turkeys open their mouths to dissipate excess heat.

Each bird reacts differently to being captured. Some birds are very calm and wait patiently to be released. Others take advantage of any opportunity to fly away or leave a mark on our hands with their spurs. These restless individuals often end up with nicknames on their capture data sheets – "Rudy" was small, but feisty; "Chuck Norris" had a thick beard and liked to kick.

To follow their movement, we attach a lightweight transmitter to each tom. The transmitter is worn like a backpack, and sits on the middle of their back with loops around each wing and the antenna running down to the tail. Since turkeys fly up into trees each night to avoid ground predators, we are careful not to tie the loops too tight, which might obstruct normal wing movements. These transmitters have a mortality switch that changes the signal if a bird has been stationary for more than eight hours.

We tune in to each bird every day to triangulate their location and listen for mortality signals. If we believe a bird has died, we quickly try to pinpoint the location and seek permission from the landowner to follow the signal and retrieve the dead turkey. We have to act quickly to have any chance of determining why the bird expired.

Frequently, we track the signal to find a transmitter attached to a pile of bones and feathers. Many scavengers, including skunks, raccoons, opossums, other birds, coyotes and weasels, will make quick work of a turkey and can pick a fresh carcass clean over the course of a night. Without evidence, we have to classify these mortality events as "unknown" cause of death and they account for 30 percent of the dead turkeys that we have documented since fieldwork began.

The most common known cause of death is hunter harvest (55%); followed by coyotes (6%), poaching (3%), capture (4%), and car collisions (2%). Any turkeys that die within two weeks of the time we last handled them we attribute to "capture," even if the cause of death appears to be from other causes.

When birds equipped with transmitters are harvested by hunters, it can lead to some humorous encounters. Normally when a hunter harvests a turkey and finds the transmitter, he or she calls the phone number on the side of the device to report the harvest. Occasionally, the hunter just does not see the transmitter while cleaning the bird or finds it and isn't sure what to do with it. We have tracked transmitted signals to hunters' garages. Imagine what they think when a stranger wearing headphones, carrying a receiver and holding an antenna rings their doorbell to ask if they've had some luck turkey hunting recently!

© Matt Lechmaier
Turkeys were trapped and fitted with radio transmitters.

© Matt Lechmaier

During the spring, we use radio telemetry to locate each bird approximately four times each week. We triangulate their position by tracking their unique radio frequency using a radio receiver, compass and GPS unit. Since 2005, we have recorded more than 2,932 locations for birds we have released. This data allows us to determine the spring home ranges for each tom.

We are also studying whether habitat characteristics within these home ranges relate to harvest rates. For example, it seems logical that birds located in small woodlots might be targeted by hunters more easily than turkeys that live in large forested blocks. If that were true, we would predict that turkey survival rates would be lower on farmlands than in heavily forested areas. And, in fact the data from our first two years bears that out. Tom turkey survival rates were lowest in the township containing the most agricultural area and least forestland. The township that is dominated by forests has the highest survival rate.

Township % Forested Area Survival Rate
Edson 22.12 0.400
Garden Valley 33.67 0.520
Albion 52.9 0.498
Mead 64.91 0.797

In addition to tracking the movements of each tagged bird during the spring, we conduct spring gobbling surveys as another measure of the relationship between the landscape and turkey abundance. This entails driving 10-mile routes in our study area at dawn, stopping each mile to stand on the side of the road and counting the number of gobblers we hear during a four-minute interval.

Occasionally an early commuter will stop to ask if we are having car trouble, which I think reflects on the helpful nature of people in our study area. I explain that I am "bird-watching" and continue to listen for turkeys once the car drives away.

We conduct these early morning surveys during April and May in several townships. I've come to appreciate these predawn travels as a real benefit of my job. I enjoy witnessing the subtle daily changes as spring progresses and just listening to the world wake up each morning is very peaceful. Dawn has become my favorite time of day.

From a scientist's perspective, these surveys have shown us that turkey abundance does indeed vary with landscape vegetation and you can expect to find the greatest concentration of turkeys with the right mix of forest to farmland cover. Turkeys are most abundant when forest comprises between 30-50 percent of the landscape, and the number of gobblers declines if forested area either exceeds or falls short of this range. On the chart, 0 represents open farmland and 100 represents dense forest cover.

turkchart.jpg - 18277 Bytes

The places in western Wisconsin where we trap turkeys to outfit them with transmitters are all on private lands, which demonstrates the importance of landowner participation and support for building strong turkey populations throughout the state. These partnerships have resulted in a remarkable wildlife management success story. Turkeys were re-introduced to Wisconsin starting in 1974. National conservation groups like the National Turkey Federation, its local chapters and a host of state conservation clubs working with DNR wildlife managers have restored a population that now exceeds 200,000 turkeys that are enjoyed by wildlife watchers and hunters alike.

Last spring, more than 200,000 permits were issued to hunters to harvest turkeys, and more than 45,000 turkeys were taken during the six-week spring hunting season. This does not include those harvested during the popular fall season from mid-September through mid-November. Research designed to better understand turkey ecology and learn more about their population levels is an effective way to improve how we monitor the health of this valuable wildlife resource. Furthermore, a healthy turkey population is a real asset for outdoor recreation. As a bird watcher, hunter, ecologist and outdoor enthusiast, I hope that these remarkable birds remain a vibrant part of Wisconsin's forest and field community.

Matt Lechmaier is a graduate student in the Department of Wildlife Ecology at UW-Madison. Initial funding for this turkey research, with the help of three research technicians, was provided by the Wisconsin Department of Natural Resources. Scott Hull, Andrea Mezera and the DNR Wild Turkey Management Committee have been an integral part of this project.