Unique study finds downed logs used extensively for predator cover before green up
Story by Mark Herwig
A first-of-its-kind study by the University of Minnesota-Duluth on woodcock chicks has found pre-flight birds made frequent use of downed logs and large branches to avoid predators before forest green up.
Researchers made these discoveries using radio transmitters on woodcock chicks ages two days old and up. Birds under two days could not bear the transmitter’s weight. Lotek NTQ2-3-2 transmitters were used for the woodcock hatchlings, a device that weighs only 0.67 grams, but costs $185.
Once the chicks grow a bit, a thin elastic thread that holds the transmitter breaks and the device falls off. The transmitters have a super thin, 6 inch antenna.
Ryan Steiner, an avian ecologist with the Natural Resources Research Institute (NRRI), University of Minnesota-Duluth (UMD), said the study began in 2019 and will continue this year. Its focus is juvenile survival rate and habitat use. The study is funded by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). It also studied two songbirds, the veery and golden-winged warbler, which unlike the rest of the country, thrives in Minnesota because the logging industry creates a lot of young forest habitat.
Of course, before you can put a radio transmitter on a tiny, exceedingly hard-to-spot woodcock chick, you must first find it. And that fun job went to Debbie Petersen and her two Gordon setters.
Petersen has a Bachelor’s degree in biology, a masters in environmental education and teaches science full time at Walker High School. Her side gigs include the woodcock study, avian point counts for several organizations, and an upcoming red-shouldered hawk survey for the Minnesota Department of Natural Resoures. She has also worked for UMD’s NRRI since 1997.
Petersen, an avid hunter and RGS & AWS member, said her Gordons are both certified Brood Pointing Dogs. Good thing, because finding woodcock chicks is no easy matter.
“When they point a hen, I first look for her and not the chicks,” Petersen said. “Unlike grouse, woodcock adults and chicks rely on staying still to avoid predators. I then flush the hen and look for the chicks, which stay motionless, especially once the ground cover starts to grow.”
Once the hen flushes, Petersen ties up the dogs and starts looking for the chicks.
Steiner picks up the story here. “The hen flies off, but then lands 10 to 50 yards away and does a broken wing display while emitting a chattering noise. If the female flies, but the young stay put. Sometimes when the chicks are ‘older’ they may try to run if they hear a sibling peeping.”
The researchers first put a flag by each chick then grab them all at once. Once the birds are fitted with transmitters, they are turned loose to hook up with mom. After that, the tracking and data collection begins, some of it quite revealing.
So far, Steiner and company have tagged 31 hatchlings, gathering 562 telemetry detections used to track the birds. And while most predation occurs on pre-flight birds, the study found a survival rate of 71% “higher than expected,” he noted.
Steiner thanked the UPM/Blandin paper company for allowing the study on land it owns near the Warba/Grand Rapids area. Three forest types there were studied: one, a clear cut 2 to 3 years old; an adjacent mid-successional site 11 to 35 years old; and a mature forest 35 years old plus.
Downed log cover
“We discovered that woodcock really love logs,” Steiner reported. “For the first 30 days of tracking, the hen was leading the juveniles around and they frequently used logs to hide. They also used large, downed branches a lot.”
The thinking is logs/branches were used as predator cover because woodcock hatch before trees and shrubs are leafed out.
“We tracked the birds and found they hide right up against the logs, to hide from predators,” Steiner said. “The other explanation for log/branch use is that woodcock eat primarily earth worms/insects, so maybe the foraging is best around rotting logs. Either way, we know woodcock use logs consistently over the spring and summer.”
As much as woodcock like hiding/foraging near logs/branches, they don’t lay eggs next to logs. The only nest they did find next to a log was predated, that is the eggs were eaten by a predator.
Speaking of predators, some very interesting discoveries were made in that regard.
“In the period before chicks can fly is when most the predation occurs, making logs even more important,” Steiner said. “From video observations, we found that chipmunks are the biggest nest predators. We also have evidence that red squirrel and weasels were eating woodcock eggs. One of our transmitters was found in a fox scat and several were found in trees, likely dropped there by owls or hawks after eating tagged chicks.”
As expected, Steiner found lots of woodcocks adults doing their mating displays in ‘dog hair aspen,” or in forestry terms, young, early successional forest. But, their nests were made and the young remained mostly in mid-successional forest (11 years plus) with high stem counts, under 3 inches, and with lots of hazelnut shrubs, aspen and paper birch.
“We counted the number tree/shrub stems in a 5 meter radius and found the woodcock were almost always in the most dense area of from 300 to 500 stems/5 meters. We found juveniles stayed in 11 to 35 year old forest really consistently. Fully 85% of our detections were in this age class forest,” Steiner said.
However, this year the researchers are going to take a second look at this finding, that is, juvenile use of mid-successional forest.
“We got some disagreement on that,” Steiner noted. “So, next year we are going test that and look at 4 to 10 year old habitat to see if that’s used by juveniles too. And we’ll look at a new site in 2021 and see if the same patterns hold true there as well.”
Forest management implications
“For an RGS member planning to log his or her land, perhaps leave larger downed branches and logs spread out, not in piles, which can attract and harbor predators. We’re not talking slash here, which is too small, but larger pieces,” Steiner said.
He said the Minnesota Forest Resource Council (MFRC) recommends leaving dead logs over 12 inches in diameter and longer than 6 feet at a rate of 2 to 5 logs/acre. Google the MFRC for more best practices information.
“And if you don’t want to sacrifice timber logs for woodcock cover, our research found large branches also work,” Steiner said.
Private forest owners and public land managers may want to have loggers leave some logs during a cut. Or, if your forest lacks log/branch cover, you can cut drop logs from older, adjoining stands into your young stands. Of course, over time, old age and the wind will also drop logs and large branches onto a forest floor.
Grouse & non-game birds
We all know that ruffed grouse use downed logs for drumming, the bird’s annual spring ritual for establishing territories and attracting mates.
“Our research areas had lots of grouse,” Steiner said. “We may someday study if or how grouse chicks use of logs.”
Many RGS members are also interested in non-game birds, such as the veery and golden-winged warbler studied by Steiner and company.
“Our woodcock results were stronger than for these other two birds, but they also like high stem count areas (these juvenile birds were also radio tagged and tracked). The difference between them and the woodcock is the warblers, for example, eventually moved into older forests and the veery nested in mid- to mature forest. They didn’t used early successional much at all,” Steiner found.
“Although, veery adults like to sing and display in clear cuts, they don’t stay there. Neither do the juveniles. One veery, however, did nest in early successional trees, but the chicks were eaten the day they fledged.”
Petersen said whatever you decide to do to improve your forest (or to advocate for public forest), you should do something.
“In a time when humans are preventing many natural forest disturbance processes (especially fire), we need to help bring about diversity in tree age and species mix on our own,” Petersen said. “A well planned logging using a stewardship plan written by a professional forester is a good way to accomplish both,” she said. “We have found that woodcock use different tree age classes for nesting and chick rearing, so work for a mix of tree age on your land,” she said.
Petersen said Blandin knows this management scheme works for wildlife. “Blandin created a diverse forest age mosaic on the land we research. In some areas they’ve done cutting in a patch mosaic, using the topography and land features, openings, water features, different age class forest, mostly aspen, to guide them,” she said.
We’ve done bird surveys in those areas and had the most grouse and woodcock in that type of forest than anywhere else I’ve worked in 20 years of bird research,” Petersen observed.
Want to become a bird bander?
Petersen said anyone with a qualified pointing dog can work toward becoming a volunteer woodcock bander in Minnesota. To work toward becoming a volunteer bander and becoming a sub-permittee in the program, training is required. The required training is offered by Pineridge Grouse Camp near Remer, Minnesota.
The camp offers a rigorous bander mentor and dog training and testing program. This year’s Pineridge Grouse Camp band training starts May 13. See the Camp’s website for details at PineridgeGrouseCamp.com.
Herwig, who lives in White Bear Lake, Minnesota, manages 44 acres of family forest southwest of Duluth. It sure has improved the woodcock and grouse hunting, he reports.