Biology of the Ruffed Grouse
| By Doug Collicutt | (Click links for more images.) |
Classification
The Ruffed Grouse is a bird (Class: Aves) related to chickens, turkeys, pheasants, quail, etc. (Order: Galliformes). It is grouped with other grouse and ptarmigan in its own family (Family: Tetraonidae). Both its scientific names come from Latin:
Genus: Bonasa - refers to "being good when roasted!" Bonus = "good", assum = "roasted". (No, I'm not kidding! That is one person's interpretation, though it may be rather tongue-in-cheek.) Another suggests that Bonasum = "kind of buffalo or bull", and refers to the drumming of male grouse sounding like the bellowing of a bull. (Yes, that's likely the more accurate, though less amusing, interpretation.)
Species: umbellus - refers to the umbrella-like ruff of feathers displayed by the male when courting females.
Description
Adult Ruffed Grouse are about the size of a bantam chicken, weighing around 500-600 g (slightly more than 1 lb) and standing about 25-30 cm (one foot) tall. Their wing span is about 50 cm, from tip to tip. Males tend to be a little larger than females with longer tail feathers, but the sexes are hard to tell apart at a glance. Their coloration will vary slightly with the seasons, being somewhat lighter in winter than in summer.
Distribution and Habitat
Ruffed grouse are found throughout Manitoba, except in the extreme north (Range Map). But they are a forest bird and are restricted to areas that have deciduous (hardwood) forests (Habitat). They are most common in the aspen dominated mixed woodlands of central Manitoba. And they are thought to do better in young or regenerating forests, which have thick shrub layers. This is a species that may be benefiting from human activities such as logging that removes mature coniferous forests, which are often replaced quickly with aspens and other short-lived deciduous tree species.
Habits
The Ruffed Grouse is a solitary, ground-dwelling bird, but is nimble and adept at clambering around in the tops of shrubs or trees, especially in winter when buds are a primary food. They seldom fly far, preferring to walk or even run away from danger. Flight is used as a last ditch effort to avoid predators. Grouse are active during the day (diurnal) and roost for the night on low tree branches (2-3 m high) under good cover, preferring the protection of spruce or fir trees if they are around.
Male grouse maintain a territory of about 4-20 ha (10-50 acres). They defend this territory and will not tolerate other males nearby. Females wander over a larger area, as much as 40 ha (100 acres), but they tend to stay on a particular home range, though this may overlap with the ranges and territories of other females and males.
Ruffed grouse remain active year round. In winter they continue to walk around on the snow surface, aided by extended scales on their toes that act like snowshoes. When they are at rest they fluff up their feathers until they look like little brown bowling balls, the spherical shape helping to conserve body heat. They will also take advantage of deep snow for shelter from the cold. After a short flight they will plunge right into the snow to spend the night secure and well insulated.
Populations
Ruffed grouse populations vary dramatically over time, both with the seasons and over the span of many years. Over the course of each year the population may swell by late summer to 3 or 4 times the spring level with the production of young. But, winter mortality rates may approach 75% in bad years. Within a given region grouse numbers tend to rise and fall in roughly a 10 year cycle, with the highest densities (#birds / unit area) reaching about 8 times the lowest levels. We couldn't track down any good population figures for Manitoba as a whole, either in terms of total numbers or densities of birds that exist here. In other parts of North America, grouse populations have been known to average around 10-15 birds / square kilometre.
Severe winters with little snow cover are hard on Ruffed Grouse. Disease, weather and predation all play roles in the population cycles of this species. But this is a species with high fecundity; that is, it can produce many young, rapidly, so its population can recover quickly.
Life Cycle
Spring, from late April through May, is mating season for Ruffed Grouse. Males "drum" to attract females to their territory. A male may drum from the same spot, using the same log or stump for several years. Males try to select the best habitat for their territory, where they and females and their chicks will be able to find food and proper shelter. But once established, the male will likely remain on his territory for life. Females wander over a larger area than males and may include the territories of several males in their home ranges. Finding food for themselves, to produce eggs, and then for their chicks is uppermost in the females mind. So, males whose territories contain the best habitat will be the most successful at attracting mates. Male grouse remain on their territories and continue soliciting for mates until early summer (females that loose a clutch of eggs to predators may try again). Then they set about feeding intensively to prepare for the coming winter. Males are not involved in the rearing of the chicks.
Hear a grouse drumming:
When the female is ready to mate she approaches a drumming male. When the male spots the female he begins to "display" for her. He expands the ruff of feathers around his neck, arches his tail feathers into a broad "fan" and struts around. His actions serve to overcome her normal tendency to avoid other grouse (Ruffed Grouse are solitary birds) and encourage her to mate.
After mating the female constructs a simple nest on the ground near the base of a tree or some shrubs. The nest is usually just a shallow excavation lined with leaves, grass or feathers. In it she lays up to 14 buff coloured eggs. The eggs are about 3.8 x 3.4 cm in size. She lays 1 egg per day, so the process of egg- laying may take 2 weeks. She incubates them for as many as 24 days, leaving the nest only briefly in the morning and evening to meet her own needs. Incubation doesn't begin until all the eggs have been laid, so the chicks usually all hatch out within the same day. In Manitoba, hatching is usually complete by mid- June. Grouse chicks are "precocial" - well developed at birth - and the entire brood leaves the nest shortly after hatching, never to return to it.
The female will lead her brood to good sites for foraging, but the chicks must feed themselves. While they are still small the chicks can find shelter beneath their mother at night and during inclement weather. She keeps a close eye out for danger, too, enabling the chicks to concentrate on the business of feeding. If a predator is spotted the female will attempt to draw attention from her brood by clucking and hissing, even feigning injury with "the old broken wing trick", to draw an attack, before bursting off the ground to safety. The chicks, meanwhile, burrow into the leave litter or under some other shelter and remain still, only emerging after the threat is gone and their mother returns. But young chicks have little defense, other than motionlessness and cryptic coloration. Chick mortality is always very high. However, by 2 weeks of age the chicks can fly to low perches and so gain an added measure of protection.
Grouse chicks grow rapidly, reaching adult size by late summer or early autumn. When they are about 12 weeks old they leave their mother, striking out on their own in search of a home range or territory of their own. They may travel 2-3 km from their place of birth. Adult males start drumming again in the fall, to re-establish their rights to their territory, not to attract a mate. Males won't tolerate other males around at any time of the year, so autumn is a tough time for young male birds. They will be driven into ever poorer habitats in search of unoccupied territories. And young females will be pushed from the ranges of other adult females, in turn searching for their own place to live. Few young birds that make it to autumn will survive their first winter.
Although it is thought that individual birds may live for as long as 11 years, the average life span for Ruffed Grouse is far less, and few birds make it beyond 7 or 8 years of age.
Diet
Grouse chicks begin their lives by feasting on insects and other invertebrates, but they will also eat plant shoots and young leaves. And they won't pass up small frogs or anything else that might fit in their beaks. Young grouse, like domestic chickens, are omnivores. As summer progresses they include flowers, berries and seeds in their diet, and insects become less important. Adult grouse eat the same types of food, but rely less on insects than the chicks, which have a much greater need for the proteins contained in animal foods. Female grouse probably eat more animal foods in spring when they are in need of more protein to produce eggs. By winter's onset, the now-grown chicks and adult birds are left with a sparse fare. Birds that haven't fattened up well before entering winter will have a hard time. The buds and catkins (the flower-like structures of birch and willow families) of woody plants are their mainstay until spring returns. Buds from birch and aspen trees, as well as willow and many other shrubs are important winter foods. Throughout the winter months it's common to see Ruffed Grouse high up in the thin branches of trees, or perched precariously in slender shrubs, picking off buds to eat. Though they do find some buds and the occasional dried berry at ground level. Spillage from bird feeders can provide grouse with extra food, too. They seem to prefer larger items such as sunflower seeds or cracked corn to the small millet-type seeds though. Grouse meet their needs for water with dew, rain droplets and moisture in their food. They tend to leave their droppings in piles where they've rested for a while.
Grouse as food!
Ruffed grouse are an important link in the food web for many predators, not the least of which are people! True to their scientific name, Ruffed Grouse are considered quite a delicacy by some. In the early 1970's, about 45,000 Ruffed Grouse were taken annually by hunters in Manitoba. One estimate from 1970 suggests that 3,700,000 Ruffed Grouse were shot that year throughout North America! (Sorry, we couldn't find any more recent figures.) There is a general consensus, however, that hunting has little overall effect on Ruffed Grouse populations. Hunters tend to pick off the displaced young birds each fall. Grouse populations are thought to fluctuate more as a result of habitat changes, disease and weather conditions.
All sorts of other predators avail themselves of this tasty bird, everything from the tiny least weasel, that can take chicks, right up to wolves that won't pass up much for a meal. Birds of prey take their share, too. Owls, goshawks, broad winged hawks and others are quick to make a meal of Ruffed Grouse. As one of our largest and most common non-migratory birds, it plays an important role in getting many predatory species through the winter each year.
Thanks for learning about Ruffed Grouse! Bye for now!
If you liked this article, here's more you might enjoy:
How Grouse Saved the World | Makin' Tracks | Snow Snakes!
Acknowledgments
The information contained in this article was drawn from a wide array of sources including web sites, books, pamphlets and personal communications. The major sources of information and, or information verification are listed below.
Ruffed Grouse - Canadian Wildlife Service, Hinterland Who's Who Series. 1973. Information Canada, Ottawa, Ont. Catalogue No. CW 69-4/15The Ruffed Grouse. 1947. Bump et al. State Conservation Dept., Albany, N.Y.
The Audubon Society Encyclopedia of North American Birds. 1982. J.K. Terres. A. Knopf Pub. New York, N.Y.
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