Hen turkey survival study backs up 1990s research
Madison — New research on Wisconsin hen turkeys finds that the birds thrive in a mixture of open land and woods better than they do in purely wooded land.
Chris Pollentier, a graduate student at the UW-Madison Department of Forest and Wildlife Ecology, is now writing his thesis on his 2010 and 2011 research findings on female turkeys in western Wisconsin.
Pollentier and his crew of technicians live-trapped and monitored 142 hens – 101 adults and 41 juveniles – over two years
“My idea was to compare and contrast the survival and productivity of hens that varied with two different landscapes – the amount of forest and openings,” Pollentier said.
He found that hens using a 50/50 mix of open (agriculture, hay, pasture, CRP) land to forest (deciduous, mixed forest, evergreen) saw higher survival.
He studied birds in the more “open” townships of Hale in Trempealeau County and Westford in Richland County, and the “forested” townships of Fairchild in Eau Claire County and Stark in Vernon County.
The study began by talking to landowners and obtaining permission to live-trap turkeys on their property.
Then a technician hid in a blind and shot a rocket net over turkeys that came to a bait pile of cracked corn.
The researchers tethered radio transmitters onto the hens’ backs and then released them.
“In a nutshell, if you just looked at survival as a whole, it was about 52 percent (when combining all four townships), which is considered normal in the literature,” Pollentier said.
“But what is interesting is that survival in the more open townships was 67 percent and survival in the more forested townships was 39 percent – a huge difference,” he said.
It didn’t seem to matter whether the open study area was north or south – hens in both open townships (Hale and Westford) saw a 67 percent survival rate. The same held true for the lower survival rate of 39 percent in the forested townships of Fairchild and Stark, regardless of their geography.
Most of the mortality occurred during nesting and brood-rearing (mid-March through mid-July), when hens are most vulnerable as they incubate eggs or shepherd poults.
After that period, the mortality leveled out, with fall survival at 85 percent to 90 percent. In the winter, about 90 percent of the hens survived.
Pollentier said that after the poults hatched, the researchers walked in to get an idea of how many hatched. At two weeks of age, survival of the poults was 36 percent and survival at four weeks was 28 percent.
“If the young birds can make it to two weeks of age, they then can generally fly up into the roost and mortality is not as great,” he said.
Regarding open areas and forested areas, poults, too, saw higher survival in the open townships, but at a different rate than the hens; 35 percent survived in open townships and 23 percent in forested townships.
Pollentier thinks that in the open areas the birds nested on habitat edges that afforded longer sight lines than those enjoyed by hens in the forested areas. The latter hens may be more vulnerable to predators sneaking up on them.
Pollentier found that hens with larger home ranges, primarily in the more forested areas, were more likely to be killed. His theory is that the hens are looking for ideal habitat, and without as many open areas they’re moving more often and are more likely to encounter predators.
Each radio transmitter had a mortality signal that told researchers when the bird had not moved in a while. They found that hen mortality was primarily from canids (coyote, fox, and domestic dogs), which totaled 72 percent of all mortality. Three percent were killed by great-horned owls, and 3 percent were killed by bobcats.
Only two of the hens fitted with radio transmitters were shot by hunters. Hens are legal during the fall, but are protected during the spring season.
“What really struck me was the amount of movement that we saw out of these birds, especially the juveniles,” he said. “If we took a straight line from where they were live-trapped, some hens moved up to 10 miles.”
Adult birds also moved, but nothing like the juveniles.
Pollentier’s results are similar to an earlier study by Matt Lechmaier, who studied movement and survival of gobblers. Lechmaier found that abundance of male turkeys was highest where there was about an even amount of forested and open land. It appears that turkeys don’t want just open areas and don’t need fully forested areas.
Pollentier’s study confirmed DNR research from the 1990s that found hen survival then was 52.7 percent; hen survival in Pollentier’s study was 52.2 percent.
“Overall, I look at this research as a way to maintain birds on the landscape,” Pollentier said.
The researchers weighed the birds they caught during the winter and found that the average weights were 8.9 pounds for juvenile hens, 10.1 pounds for adult hens, 13.4 pounds for jakes, and 19.2 pounds for gobblers.
Looking back on his two years of field research, Pollentier said he can’t believe how elusive the birds can be. When walking in the woods and knowing that there were birds nearby with radio transmitters on them, he could sometimes get within 50 feet of a bird and not see it.
“Their keen eyesight and senses are so good, they see you way before you see them,” Pollentier said. “And, when we monitored birds that were hanging around a specific area, we’d often find the bird nesting.”
Pollentier thinks the DNR could take this information into consideration when deciding how many permits to issue to turkey hunters based on the amount of forest cover in different areas.
The study was funded by state turkey stamp money.