Researchers look for insight into wild turkey decline

The reintroduction of wild turkeys to Iowa’s landscape has been celebrated as a conservation success story for the past 25 years. But Iowa’s turkey population is showing troubling signs: the numbers are down, nests are failing and fewer poults are surviving.

And it’s not just an Iowa problem. Turkey populations are declining in all states in the Midwest and across the eastern half of the United States.

A group of Midwestern states met in North Dakota in 2023 to discuss turkey population concerns and projects that are planned and underway. Missouri has had a decades-long study, while Ohio, Nebraska and Wisconsin are all in the early stages of projects.

In the southeast, Tennessee is looking at harvest seasons impacts and Auburn University is looking at male fertility rates in Alabama.

In 2022, the Iowa Department of Natural Resources began a 10-year study of the turkey population in southeast Iowa to learn more about why the numbers are declining. Now entering its third year, the study may be giving researchers more questions than answers.

Dan Kaminski, wildlife research biologist with the Iowa DNR, is leading the study. What Kaminski and his fellow researchers have learned is that only around 60% of Iowa hens survive annually.

Of the hens that are alive on April 15, roughly 25% will not nest. That’s more than other researchers are finding in other parts of the country.

Researchers observed 60 nests last summer and documented 10 nests that hatched. Of those 10 nests, only 30% of the broods survived at least one poult into August.

All of the unhatched eggs collected from lost nests were sent to the University of Tennessee for examination and all were determined to have been fertilized.

“These are concerning findings, but the study only goes back two years,” Kaminski said. “The ten-year study will get us out of any short-term weather patterns that affect turkeys and provide clearer long-term data trends.”

So, what is killing them? Environmental factors? Lack of available food? Predators? Abandonment?

The Project

Researchers in Wisconsin found that to sustain its current population, hen turkeys need to average 2.6 poults per hen. The recent trend in Iowa’s summer turkey brood survey has hens averaging two poults per hen.

To find out what is causing nest failures, poult mortality and why a quarter of the hens are not even attempting to incubate a nest, researchers will be catching hens in late January and February, outfitting them with transmitters and releasing them.

“Cold and snowy conditions are best. That will group up the birds,” Kaminski said. “Our local staff have trail cameras set up at wintering sites and once the birds show up, we head to the sites and trap the birds.”

Nesting season begins in late April, peaks around May 20 and ends in mid-July. Turkeys nest on the ground, usually in dense vegetation underneath shrubs or trees in overgrown fields or mature forests, relying on their natural camouflage to avoid predators.

The transmitters update hen location every 15 minutes and once it appears hens are on a nest, Kaminski will mark and date the location, and then wait.

Hens will lay one egg every day-to-day-and-a-half, averaging 12-14 eggs per clutch. Eggs incubate for 28-30 days before hatching.

After hatch, little by little, the hen will slowly begin to move her brood away from the nesting site. Once she is on the move, researchers will go in to check nesting success, collect any unhatched eggs as well as any eggs that appear to have been broken or eaten.

“With the new technology — the satellites and GPS — it makes collecting highly detailed data much more available,” Kaminski said. “When birds set up nests, we want to know about it. If it fails, is predated or abandoned, we want to know ASAP. We want to get to the nest to see what happened and collect the eggs for analysis.”

This year, researchers will attempt to catch 83 adult and juvenile hens across all sites in Lucas, Van Buren, Louisa and Jackson counties. These birds will join the roughly 55 birds that are currently “on the air.”

The goal is to maintain 25 birds with transmitters in each county.

The study area is a mosaic of grassland, agriculture and timber that should be producing turkeys — but is not. And the issue is not isolated to southeast Iowa. Other well-known turkey spots in northeast Iowa and the Loess Hills are also seeing the same declines.

“But those areas started with more birds so the population decline isn’t as obvious,” Kaminski said.