Ruffed Grouse
| Scientific Name | Bonasa umbellus |
| Survival Strategy | Active All Winter |
| Conservation Status | Least Concern |
Spring
Male ruffed grouse intensify their drumming behavior in spring to attract hens into their territory. Males will mate with multiple hens (polygamous) and have no role in raising the chicks. After mating, hens build a nest in a sheltered location and lay 9 to 14 eggs. Hens incubate the eggs for 24 days, after which the fully feathered grouse chicks can walk and feed themselves almost immediately (precocial). A few hours after hatching, the chicks imprint on the hen and follow her away from the nest site.
Summer
Ruffed grouse hens continue to care for their chicks for 12 weeks.
Fall
By September, the surviving members of the brood are old enough to be independent of the hen. Pectinations form on the sides of their toes, and new feathers cover the upper parts of their feet and their nostrils.
Winter
Winter survival of the ruffed grouse depends on the available food supply, mainly the buds of trees such as aspen, hazelnut, birch, and maple.
Behavior
Imprinting
Like most precocial birds, the survival of newly-hatched ruffed grouse chicks depends on quickly forming a social attachment (imprinting) to the hen. An imprinting window lasts a few hours, after which the birds have bonded with the hen. Shortly after hatching, the hen will lead her brood away from the nest site and the smells that attract predators. Chicks unable or unwilling to follow are left behind. The young birds learn what to eat and how not to be eaten through imprinting.
Imprinting can sometimes go wrong, and a chick may imprint on something other than the hen. If the hen is away from the nest during the critical imprinting window, the chicks may imprint on the first large moving object they see. Grouse have imprinted on cats, dogs, humans, and in one case, a farm tractor.
Snow Roosting
On cold winter nights, ruffed grouse will occasionally dive headfirst into a snowdrift and remain buried until morning. Although this sounds counterintuitive, the insulation provided by the snow keeps the grouse much warmer than the outside air. The temperature will still be below freezing inside the snow roost, but the grouse will be protected from the lethal winter air not more than a few feet above its head. Drifting snow will conceal the opening, adding protection from predators. The heart-pounding thrill of a startled ruffed grouse exploding out of a snowdrift is an experience a hiker will never forget.
Drumming
An iconic sound of the Northwoods is the drumming of male ruffed grouse. Perched on a hummock or fallen tree, the grouse fans out his tail feathers, raises his ruffs, the feathered epaulets on his shoulder that give him his name, and begins his performance. The bird produces the percussive sound by beating his cupped wings against the air in a process similar to those folded paper poppers that were once common in middle schools. The performance lasts 8 to 10 seconds and can reach speeds of 5 beats per second. The drumming and accompanying display attracts females for mating and warns other males that this is his territory. Although the male grouse produces these loud thumping sounds throughout the year, the behavior is more common and intense in late March or early April.
Physiology
Pectinations
In the fall, ruffed grouse develop a row of comb-like scale extensions called pectinations on either side of their toes (the term has its roots in the Latin word pectinātus, which means “combed”). The addition of hundreds of tiny pads of cartilage produces a snowshoe effect that helps the bird stay on the surface of deep snow. These pads also provide extra grip when grouse roost in trees or as they make their way down thin outer branches to forage on buds and catkins. This slip resistance is similar to traction gained when people strap cleats to their winter boots. The pectinations fall off in the spring.
Extra Leg Feathers
In late fall, grouse grow a layer of leg feathers that help conserve body heat. These feathers extend down over the bird’s fused ankle and foot bones (tarsi). The tarsi of birds are often mistaken for legs. What looks like backward-facing ‘knees’ are, in fact, the bird’s ankles.
Feather-covered Nostrils
Any child on a sledding hill knows that a scarf over their nose will trap some of the heat from their exhaled air and will warm the cold winter air as they inhale. This same process works for ruffed grouse that grow feathers extending down their beak to cover their nostrils in winter.
Benefits of a Crop
With so many predators searching for a winter meal, the ruffed grouse increases its chance of survival if it stays hidden in the brush. Unfortunately, the food source that gets the bird through the winter is the buds and catkins found on the thin tips of tree branches. Spending time exposed in a leafless tree canopy is an open invitation to predators. To reduce predation risk, a ruffed grouse will quickly swallow enough edible plant parts to fill their crop, an enlarged portion of the esophagus that stores undigested food. After twenty minutes of foraging in the open, they digest their food in the safety of the dense underbrush.
Diet
The diet of the ruffed grouse depends on the seasonal availability of foods found in their mixed-age forest habitat. During the spring and summer, adult grouse feed on leaves, buds, and fruits, while young chicks feed on protein-rich insects and other invertebrates. In the fall, grouse will seek out acorns and soft fruits. Their ability to digest cellulose allows them to feed on the buds, twigs, and catkins of aspen, birch, and willow throughout the winter.
Lifespan and Mortality
The first year of life is the most lethal for ruffed grouse, with only 8% of grouse chicks still alive the following year. Grouse that survive their first year may live for 2-3 years.
Predators
Ruffed grouse are an essential food source for goshawks, great horned owls, and foxes.
West Nile Virus
Ruffed grouse are highly-susceptible to West Nile Virus, a mosquito-transmitted disease, with reported mortalities as high as 90%.
Climate Vulnerability
When winter temperatures fluctuate above and below the freezing point of water, the snow becomes too icy for snow roosting, eliminating a vital survival adaptation of the ruffed grouse. Extreme temperatures and rainfall events associated with a warming climate will reduce nesting success.
Audubon’s climate model suggests that a range loss of 17% to 52% is likely, including a shift out of the lower 48 states.
Never Stop Learning
First Nations: The Ojibwe word for ruffed grouse is “bine.”
Literature: A quote from Aldo Leopold, in A Sand County Almanac; “Everybody knows that the autumn landscape in the northwoods is the land, plus a red maple, plus a ruffed grouse. In terms of conventional physics, the grouse represents only a millionth of either the mass or the energy of an acre. Yet subtract the grouse and the whole thing is dead.”
References
| Rusch, D. H., S. Destefano, M. C. Reynolds, and D. Lauten (2020). Ruffed Grouse (Bonasa umbellus), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.rufgro.01 | |||
| Haupt, J. 2001. “Bonasa umbellus” (On-line), Animal Diversity Web. Accessed December 27, 2021 at https://animaldiversity.org/accounts/Bonasa_umbellus/ | |||
| Naturally Curious with Mary Holland: grouse digestion https://naturallycuriouswithmaryholland.wordpress.com/tag/ruffed-grouse-digestion/ | |||
| Imprinting in Birds | Dan Gleason’s Blog https://dangleason.wordpress.com/avian-biology/172-2/ | |||
| How Climate Change Will Reshape the Range of the Ruffed Grouse https://www.audubon.org/field-guide/bird/ruffed-grouse?adm1=WI&country=US#bird-climate-vulnerability | |||
| The Scientific Impact of West Nile on Ruffed Grouse https://ruffedgrousesociety.org/the-scientific-impact-of-west-nile-on-ruffed-grouse | |||
| Leopold, Aldo, 1886-1948. A Sand County Almanac, and Sketches Here and There. ©1949, 1949. https://www.aldoleopold.org/store/a-sand-county-almanac/ | |||
| Ojibwe People’s Dictionary: Ruffed Grouse https://ojibwe.lib.umn.edu/main-entry/bine-na | |||
| Grouse facts: Ruffed Grouse Society & American Woodcock Society https://ruffedgrousesociety.org/grouse-facts/ | |||