Late last summer, biologists teamed up with a University of Maine professor to begin a project that will provide a clearer picture of the state’s ruffed grouse population.
Using radio tags, the researchers are monitoring those birds and compiling data on their survival rates and breeding success.
A glimpse at the data collected so far indicates that the grouse in two study areas — one southwest of Bangor, the other in a commercial timberland east of Old Town — struggled through a bitter winter that is still holding on in some regions.
“We’re down to 41 [grouse alive] out of 106,” said Brad Allen, the Maine Department of Inland Fisheries and Wildlife’s bird group leader. “So throughout the hunting season and throughout the winter, 62 percent of them have died.”
Allen said it didn’t appear that hunting was the main cause of death, however.
“At the site to the west of [Bangor], 10 were shot out of 60. That’s 17 percent,” Allen said. “On the commercial timberland, six of 46 were shot, so that’s 13 percent. Just averaging, about 15 percent of the birds that were on the ground on Oct. 1, [which was the first day of hunting season], were taken by hunters, which is well within the framework of other studies that have looked at hunting mortality in grouse.”
Kelsey Sullivan, the game bird biologist for the DIF&W, said that the radio transmitters attached to each bird in the study gives off a specific signal to indicate when a bird has died.
“If they’re stationary and there’s no movement whatsoever for eight hours, it goes from one [transmitted] blip every half second to two blips every half second,” Sullivan said. “And [the transmitters] are pretty sensitive. If it moves just a little bit, it will send the signal. It has to be very still for an eight-hour period, and that’s typically a dead bird.”
Despite losing 62 percent of the study group, neither biologist is overly concerned.
“[When compared] to other studies of mortality, we were on the high end of normal,” Sullivan said. “It wasn’t out of bounds for what you could expect, but it was definitely on the high end for what’s been found in other states.”
Allen said the data that’s being gathered is especially important because it will allow Maine biologists to track trends that exist in the state rather than extrapolate based on data gathered in other states.
“The [University of Maine] professor, Erik Blomberg, points out that the literature lacks information on winter survival of grouse in northern climates,” Allen said. “There haven’t been any recent studies on birds in the north. They’ve studied birds in the Appalachian region and other places.”
This winter’s data seems to fly in the face of conventional wisdom, Allen said, but shows that there are a number of factors that contribute to winter survival rates.
“The conventional wisdom for deep, powdery winters is that it’s better for grouse because they can hide under the snow and spend the night in their night roosts and be away from predators,” Allen said.
Crusty snow, Allen said, has been thought to be a threat to grouse, which become unable to burrow into a night roost.
This year’s snow conditions in the study areas was largely powdery, but that opens the birds up to another threat, especially when it’s extremely cold.
“It’s kind of interesting. What goes on during a winter when it’s super cold, an animal has to feed more,” Allen said. “And if you have to be out and feed more, you’re more vulnerable to predators.”
Allen said the birds may have died as a result of the extreme cold, but more data will help inform biologists.
“Maybe next year will be different,” he said. “That’s why you study for several years.”
The study will move into another phase in the near future, and biologists face a challenge that the loss of birds has created.
“One of the downsides of this is that a major part of this project is to study nesting ecology and we have fewer females going into the spring than we would have liked,” Allen said. “We have 11 at one study site and only four at another. So our goal is to get some more birds radioed before the nesting period. Like now. As soon as we can get into the woods.”
John Holyoke can be reached at firstname.lastname@example.org or 990-8214. Follow him on Twitter: @JohnHolyoke.