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Iowa’s wild turkey population is declining. Researchers are working to understand why
Decades after turkeys were reintroduced to Iowa and hunting returned, fewer hens and poults are surviving, which could spell trouble for the bird’s future
Aug. 11, 2024 5:00 am, Updated: Aug. 12, 2024 8:16 am
Fifty years after he began hunting wild turkeys in Iowa, Gary Reeder’s pulse still quickens and the hair on the back of his neck stands up when he sees a turkey in the distance.
“It’s like a religious practice for me,” said Reeder, of Manchester. “It’s so therapeutic; it’s how I feel most close to God.”
Reeder was 19 in 1974, when he participated in Iowa’s first turkey hunting season, which followed years of work by the state to reintroduce the birds.
Reeder started regularly hunting turkeys in the 1980s. Since then, he’s kept track of the number of turkeys he sees.
“I have a pretty good idea of the ups and downs,” he said.
In the 2010s, Reeder started to notice changes in the population. He wasn’t the only one.
According to data collected by the DNR, the harvest of juvenile male turkeys — called “jakes” — fluctuates each year, but has shown decline. From 2007 to 2024, the largest annual harvest recorded was 2009, with 1,218 jakes. The smallest harvest was 2021, with just 893 birds.
In 2022, the Iowa Department of Natural Resources launched a 10-year study looking into the wild turkey population in southeast Iowa to try to determine why it’s declining.
Dan Kaminski, a wildlife research biologist with the DNR, is leading the study. He said trends show gradual decrease. In southeast Iowa, for example, harvest records report the turkey population has declined an average of 0.76 jakes per year.
The study is specifically working to determine why fewer hens and young turkeys — called “poults” — are surviving.
It’s not just an Iowa problem. Researchers in Missouri, Ohio, Nebraska, Wisconsin, Tennessee and Alabama are undertaking similar projects.
A study published in the Journal of Wildlife Management in 2020 reported that in the southeastern U.S., only 7 percent of turkey broods — defined as a group of wild turkeys made up of at least one adult hen and poults — successfully survived at least one poult past four weeks old.
Through their research, Kaminski’s team has found that about 60 percent of hens studied survive annually. Some hens die shortly after nesting. Of the hens alive at the start of the nesting study, Kaminski said 25 percent did not incubate a nest.
“It doesn't mean that they didn't attempt to lay eggs and those nests were lost before incubating — that we cannot know — but it means that a quarter of birds alive in mid-April will not sit on a nest,” he said.
Of the 60 nests Kaminski’s team observed last summer, researchers documented only 10 nests that hatched. And of those 10 nests, only 30 percent of the broods had at least one poult survive into August.
“Hen and poult production has declined over time and those two factors are really what’s probably driving the population decline,” Kaminski said. “But why those factors have changed, that's kind of the million dollar question that everybody's trying to answer.”
The DNR has pointed to research in Wisconsin that found to sustain its current population, hens need to average 2.6 poults per hen. The trend in last year’s Iowa summer turkey brood survey showed an average of two poults per hen.
The decline of the eastern wild turkey — the subspecies of bird that is native to Iowa — has been worse in some places than others, said John Burk, a district biologist with the National Wild Turkey Federation.
Burk said since the 2000s, for example, the wild turkey harvest in the northern region of Missouri has declined close to 60 percent.
“Turkey harvest does have a tendency to be pretty reflective of what the population is doing because it is usually pretty proportional and that is why we use it,” Burk said. “When you have a lot of turkeys, you’ll have a lot of turkey hunters, and they will shoot a lot of turkeys. When turkey numbers decline, hunter numbers will decline, as will the harvest.”
Turkeys are an Iowa success story
Wild turkeys were reintroduced to Iowa in the 1960s, after being wiped out in the early 1900s through hunting and habitat loss.
The Iowa Conservation Commission — now known as the Iowa DNR — released Missouri turkeys at state parks in southern Iowa, and over time the birds began breeding and expanding their range. In 1974, there were enough turkeys to hold a limited hunting season in southern Iowa. By the late 1980s, turkey hunting was allowed statewide.
After the initial boom in the 1980s, Kaminski said researchers started seeing turkeys decline again the 1990s.
“And there’s still speculation on why that might be,” Kaminski said.
Jim Coffey, a forest wildlife research biologist with the DNR, said the science behind understanding why some turkey subspecies thrive and others struggle is “tricky.”
“We were blessed with expanding populations through the ‘70s and the ‘80s, and so [we] just assumed that things would always be good,” Coffey said. “We should not have been so shortsighted to realize that things don’t change over time.”
Coffey added that the kind of in-depth research into wild turkey habits and populations that’s being done now has not been done since the 1990s.
Habitat changes, insect numbers, weather may be factors
Researchers are working to determine what’s behind changes in the turkey population, but Kaminski said the driving forces could include habitat changes — the loss of grassland across the state — and the loss of insects, which poults eat after they hatch.
“That’s a real key food source for poultry after they hatch, so as they are developing, that kind of high-protein loss could drive some of that,” Kaminski said.
Coffey said weather also is a factor in ground nesting birds’ survival.
Turkeys nest on the ground in April and May. They prefer areas with dense vegetation, usually under shrubs or in overgrown fields or forests.
“Typically, cold, wet springs will decrease nesting success and has an impact on young birds’ ability to find food and thermo-regulate,” Coffey said. “Moderate droughts are typically beneficial to poult production.”
One other factor that could affect turkey population is a disease called lymphoproliferative disease — LPDV — that was first found in an Arkansas turkey in 2009.
Rachel Ruden, a state wildlife veterinarian with the DNR and an affiliate assistant professor at the College of Veterinary Medicine at Iowa State University, said about 25 percent of turkeys tested by the DNR have been exposed to the virus. The disease is largely fatal for the birds who contract it, Kaminski said.
“They’ll get tumors [and] they’ll get cancer,” he said. “If they live long enough, they’ll die.”
Kaminski said the main concern around LPDV is how it will affect turkeys and poults in the poultry industry.
“The birds are in pretty tight confines, so a disease like that could spread quite a bit more readily, but we don’t know how it acts in wild turkey landscapes yet” Kaminski said.
Research includes GPS transmitters, egg testing
As part of their study, Kaminski’s team has tagged hens with GPS transmitters that track the birds’ location every 15 minutes using cellphone towers. Kaminski said through this they have been able to track the turkeys in “real time” to follow their nesting and survival tendencies.
“With that we are looking at just a lot of the kind of movement ecology, home range sizes, how turkeys utilized land,” Kaminski said, adding that Iowa landowners have helped with the research by allowing the DNR to access land to observe the turkeys. “We're getting some good habitat use information.”
While the DNR does not have population estimates statewide historically, Kaminski said one of the goals of the study is to collect reliable population data to help develop a model to estimate population sizes. He said the information they are collecting includes survival, fertility and motility rates.
Besides tracking movements of the turkeys, the researchers also look at where the turkeys are building their nests, laying eggs and where their poults are hatching.
The researchers collect eggs and send them to two different labs.
If the eggs from unhatched nests are whole and not broken, they are sent to the University of Tennessee. There, university researchers open the eggs and look at their fertilization rates. All of the eggs collected last year were fertilized.
If the eggs have hatched or are broken, they are sent to Luther College in Decorah where researchers are working with a geneticist looking at the sex ratios of the clutches.
Ruden, the wildlife veterinarian, is working in two phases of the project. When wild turkeys and hens are captured by the DNR in the winter, Ruden takes the birds’ blood samples to test for diseases. She said the researchers also take the birds’ plasma to screen later for possible future diseases.
The turkeys are fitted with a GPS tracker when their blood is drawn.
The other half of Ruden’s role involves monitoring the turkeys’ mortality signals, so technicians can go out and collect the birds’ carcasses when they become available. Ruden said this isn’t always feasible since some birds die of natural causes, while others are killed by predators.
No push to change hunting regulations
Despite the turkey population decline, Kaminski said there has not been a push to change turkey hunting regulations in Iowa.
“We primarily only harvest male turkeys, and the way I look at it is, it doesn't matter how hard they try, but none of those males are ever going to lay an egg, and that's really where populations are being driven right now,” Kaminski said.
He added that in Iowa, the fall harvest reports predominantly male turkeys being hunted, with only about three hens per county recorded in the annual fall harvest.
Kansas has cut back its harvest and has limited non-resident hunting in the state, Kaminski said. Tennessee conducted a study to determine whether changing harvest zones to allow for a longer turkey breeding season would increase poult production, but the results didn’t show a population increase.
Despite Iowa’s changing landscape from human activities like agriculture and development, Coffey said turkeys are dynamic birds. Kaminski agreed.
“We just came off a record harvest in 2023,” Kaminski said. “We still have a vibrant turkey population and when the nesting conditions are right, the population can really jump.”
Kaminski said turkeys are one just part of the ecosystem, but they’re a piece worth understanding and protecting.
“Turkeys are just one bolt in the machine … you can lose bolts and the machine will still run. But if you lose too many of those bolts, it’s going to fall apart,” he said. “Turkeys aren’t just a part of our environment in Iowa, but they are a part of our heritage and our culture. If we lose the turkey in Iowa, we could lose some of that heritage as well.”
Participate in Iowa’s Wild Turkey Survey
Every year, in July and August, the Iowa Department of Natural Resources conducts its annual wild turkey production survey. Wild turkey sightings are recorded to estimate this year’s nesting rates and nest success.
To participate, note the date and county in which a turkey is seen, if it was an adult female or adult male (males have beards on their breast), and how many poults (baby turkeys) were present.
The survey is available online at iowadnr.gov/Hunting/Turkey-Hunting/Wild-Turkey-Survey. There is a guide on documenting wild turkey broods on the survey website, that provides tips on how to determine males from females, and different flock scenarios with poults of different ages.
Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.
Comments: (319) 398-8370; olivia.cohen@thegazette.com
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