For the Ruffed Grouse, or Partridge, Winter Survival is a Real Challenge
Dispersal, finding food and survival are three of the main challenges that ruffed grouse, locally known as partridge, face every fall and winter. The manner in which they confront each of these tasks prove ruffed grouse to be one of the most adaptive species of overwintering Upper Valley birds.
The challenge of dispersing falls to the young of the year. By the time they are a little over four months old, grouse begin leaving their brood. Males are usually the first to leave, perhaps because they have a more rigorous search ahead of them. It is very important that they find a territory to claim before winter, as research indicates that the males with established territories are the most successful at attracting females in the spring. Their quest is not a simple one. They must find an area that has not already been claimed by an older male, plus one that is suitable for winter survival (plenty of food) as well as spring drumming (a courtship ritual that males perform by beating their wings, often while standing on a log). This is a formidable task, and it is not unusual for a young male grouse to return to its brood several times before finding an appropriate territory for itself. Young females also are searching for territories, especially those with good nesting cover. Males tend to travel about 250 yards per day, while females wander roughly 500 yards at a time. Males usually travel one to two miles before finding an appropriate area, while females have been known to travel up to 10 miles (but usually less).
Locating food during the fall usually isn’t very difficult — acorns, mushrooms and berries are abundant. But eventually grouse are forced to switch their diet from mostly fruits and nuts, which are either gone or buried by snow, to buds. By October or November, most grouse have returned to trees as the main source of their diet. Aspen buds and catkins (flower buds) of hazel, alder and birch sustain them through the winter. Because a grouse stores very little fat, it must eat daily during the colder months. It confines its exposure to predators by rapidly feeding for 15 to 20 minutes twice a day, storing this food in their crop and digesting it later, under cover.
Diet changes aren’t the only way in which grouse adapt to winter. In the fall they grow comb-like fringes, or pectinations, on either side of each of their toes, which act as snowshoes and ice-grippers for travel on snow or icy branches. Come spring, these adaptive structures will disappear. Feathers on their legs grow thicker and farther toward their ankles to provide better insulation. Similarly, feathers on their beaks increase and grow over their nostrils, so as to slow the cold air and allow it to warm up before being inhaled.
Protection from the frigid air as well as from predators is achieved through what is called “snow roosting.” If there are 10 or more inches of snow on the ground, grouse spend the night in it. They dive head first into the snow, leaving only a small hole, with little or no scent trail for predators to smell. They then burrow in five or ten feet and hollow out a small cavity where they spend the night. Here they are hidden from owls, foxes and other predators. In addition, they are well insulated by the snow — it rarely goes below 20 degrees F. in these cavities, regardless of how cold it is outside. This represents an energy savings of 30 percent or more compared to spending the night in the open. In the morning they explode out of the snow, usually leaving wing prints by their exit hole. A cold winter without snow or a winter with frequent crust on top of the snow promises high mortality for grouse.
The ability to survive the rigors of a New England winter is no small task for any living creature, much less one that is at the top of so many predators’ list. Considering the lack of cover, food and warmth in a pear tree in winter, you wonder how they ever came up with the first line of “The Twelve Days of Christmas!”
Mary Holland is the author of “Naturally Curious: A Photographic Field Guide and Month-by-Month Journey Through the Fields, Woods, and Marshes of New England” and “Milkweed Visitors.” She has a natural history blog which can be found at www.naturallycuriouswithmaryholland.wordpress.com .