When it comes to game pursued by hunters, few face more threats than wild turkeys. Agricultural practices, diseases and a host of mammalian predators can all end the life of a chick before it begins.

“Everything from blue jays to coyotes to snakes eats turkey eggs,” said Jim Coffey, a wildlife research biologist for the Iowa Department of Natural Resources. “And just conducting targeted removals of one predator doesn’t really work. Studies show that when you suppress one predator, it opens the door for others, so you’re really not impacting overall nesting success.”

What states also know is that, for decades, turkey populations across the country have declined. Since 2004, University of Georgia professor Dr. Michael Chamberlain and his colleagues estimate that the population has decreased 9-16%.

Coffey and his colleagues are currently conducting a 10-year longitudinal study in southeast Iowa to determine what’s behind dwindling turkey numbers. The study represents a comprehensive collaboration with many partners, including Iowa State University, Luther College, the National Wild Turkey Federation, Turkeys for Tomorrow, the University of Tennessee and the U.S. Department of Agriculture. Now in its third year, researchers seek a host of factors impacting turkeys in the Hawkeye State and make management recommendations for increasing the population. What they learn can be used by other states to improve turkey populations, putting more turkeys in the fields and woods. Let’s take a closer look at the study, examine some preliminary findings and discuss how important the Iowa project is to both turkey livelihoods AND turkey hunters.

The Study

The Iowa project is the most comprehensive study ever undertaken to identify turkey population dynamics and offer recommendations to increase turkey populations. The 10-year study has four main objectives:

1. Determine female population demographics. Like most states, Iowa currently makes turkey management decisions using outdated data collected in the 1990s. Population studies are expensive, time consuming and require numerous specialists collaborating to understand all that could be driving population declines. Iowa researchers are collecting demographics like body condition data, hen/brood survival rates and nest survival rates. Data on turkey dispersal, home ranges, seasonal habitats and nesting habitat selections are also being collected.

2. Identify factors that increase mortality for hens and clutches. Researchers use tracking devices to monitor hen mortality, while weekly flushes of broods provide poult mortality information. Wild predators do take a big bite out of turkey populations, but diseases, exposure to toxins and poaching also cause significant reductions.

3. Determine diseases impacting turkeys. Researchers are mainly studying the lymphoproliferative disease virus (LPDV), a sickness first found in domestic turkeys in Israel that’s made its way to wild turkeys in North America. Initial testing in Iowa has revealed that about 20% of hens are LPDV-positive, but researchers want to learn much more about the virus.

“In some states, studies usually done by testing harvested turkeys have found that about 50% of turkeys have LPDV, and it’s 70-80% in some Canadian provinces,” said Dr. Rachel Ruden, state wildlife veterinarian for the Iowa DNR. “We are really in the documenting phase, so we want to learn its prevalence, but also what it means for our turkeys.”

4. Develop a population model for Iowa. After analyzing the data, scientists will identify what demographic and habitat improvements are needed to increase populations and offer recommendations for better managing turkeys.

Researchers use net launchers to capture adult hens annually in January and February. They then measure, weigh and take a blood sample from each bird. A sample of birds have their oral cavity swabbed to test for diseases. Scientists then place a VHF/GPS transmitter on each hen to closely monitor its movements. The GPS module transmits data every 15 minutes, while the VHF transmitter locates hens nesting in deep ravines or wherever GPS technology fails. About 100 hens will be tracked each year.

A major focus of the study is to record the nesting habits of hens to determine nesting success rates and factors impacting nesting habits. The tracking devices enable researchers to locate each hen sitting on a nest and monitor incubation. The technology tells researchers when a hen has left the nest, either due to a successful incubation or abandonment, enabling scientists to move in to investigate. If there was a TV show called “Turkey CSI,” this would be it.

“For each hatched egg, we swab the entire egg to collect DNA material to determine the sex of the poult and its entire genetic profile,” explained Dawn Reding, Ph.D., associate professor of biology at Luther College. “We also swab eggs that were predated to collect saliva samples to determine the animal or animals that predated them.”

A main project component involves comparing the habitat characteristics of successful nests to unsuccessful nests that were invaded by predators.

“We want to know what the habitat looks like at successful nests and how it’s different from unsuccessful ones, so we can make recommendations for creating and maintaining successful nesting habitats,” said Iowa DNR wildlife research biologist Dan Kaminski, who, along with Coffey, is the co-principal investigator for the project.

Preliminary Findings

The Iowa study is only in its third year, so no definitive findings or conclusions can be made. Nonetheless, initial observations of the preliminary data paint somewhat of a grim picture for nesting success and hen and poult survival rates.

So far, researchers have found about 60% of adult hens being tracked survive more than one year. This is lower than national averages reported by the National Wild Turkey Federation in 2021. Researchers believe that disease, habitat loss and predation are mainly responsible.

One key preliminary finding that stands out is the percentage of adult hens that are incubating nests in Iowa. While other states have found about 90% of hens sit on a nest, so far only 75% of hens in Iowa are nesting – 25% don’t incubate any eggs.

“Why that percentage is so high is something that we just don’t know, but we hope future data will provide some answers,” Kaminski said.

In looking at successful nesting rates, defined by at least one poult hatching, initial data reveal that turkey mothers are struggling. From 2022-23, only about 16% of adult hens produced a successful nest. For successful nests, researchers have observed about two poults per hen surviving at least six weeks after hatching.

“The greatest mortality of poults occurs in the first few days post-hatch, and theoretically declines after 4 weeks of age when poults can roost in trees,” explained Kaminski. “Some studies have indicated that you need about 2.6 poults per hen to stabilize the turkey population. In general, if you’re only at two poults per hen, you’re probably experiencing population decline.”

Another part of the project is to collect unhatched eggs to determine factors impacting hatching rates. So far researchers have collected 75 whole eggs that never hatched. Eggs are preserved and sent to researchers at the University of Tennessee to determine fertilization rates and test for diseases and genetic issues that could explain why hatching didn’t occur.

“One thing we are investigating is whether LPDV-positive hens have a higher percentage of malpositioned fetuses in their eggs. Essentially, the chick can’t access the air cell and get out of the egg,” said Ruden.

Mammalian predators like bobcats, coyotes and raccoons can’t be blamed for all predation of eggs. Researchers found one nest that had been inadvertently run over by a mower. Tail feathers from a sitting hen were found at a different nest where a cow had walked over it. Ruden notes that she’s also found the DNA of as many as three different predators at just one nest, making it difficult to determine which one initially predated it.

Kaminski notes the entire study wouldn’t be possible without buy-in from landowners.

“Most of our captures take place on private land, so we need permission from landowners. When we approach them to explain our project and get permission onto their land, many tell us they’ve seen the population decline and they’re glad someone is doing something about it.”

Other states are closely following the study because similar population declines have been occurring for decades across the East and Midwest. The data and results can be used by other state wildlife agencies to improve turkey populations throughout the country. For example, states can use the Iowa project to develop habitat management plans and successful nesting protocols that support population growth.

To put it in turkey parlance, results and recommendations from the Iowa study are just the tip of the beak for changing turkey management throughout the country.