Winter Adaptations of the Ruffed Grouse
Ruffed Grouse have both behavioral (diving into the snow on cold nights) and physical strategies for dealing with the cold, snow and ice of New England winters. Three of the physical changes that take place in the fall are evident by looking closely at a grouse’s legs, feet and beak. The feathers on its legs grow thicker and further down towards its feet, to provide better insulation. Small comb-like growths of skin, called pectinations, develop along either side of each toe. These increase the surface area of a grouse’s foot, and serve as snowshoes in deep snow. They also help the grouse cling to icy branches while it quickly snips off poplar and other buds at either end of the day. And on its beak, feathers expand downward to cover its nostrils, slowing the cold air and giving it a chance to warm up before it is inhaled by the grouse.
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Spruce Grouse Foraging
While Ruffed Grouse are plentiful throughout most of New England, one has to go to northern Vermont, New Hampshire or Maine to see its cousin, the Spruce Grouse. Associated with boreal forests, this largely herbivorous bird feeds primarily on the needles of pine, spruce and fir (a small amount of animal matter is consumed in the summer as well as ground vegetation). Especially in the winter, a large volume of conifer browse is consumed in order to meet energy demands.
The grouse holds the needle between the tips of its mandibles and breaks it off by flicking its head. This action, and the fact that Spruce Grouse feed exclusively on needles in the winter, leads to the wearing off of the tip of the bird’s upper mandible by spring.
If you are searching for a Spruce Grouse, you might want to concentrate in the middle of the crowns of trees, as this is where the birds tend to forage. Theories for this preference include the fact that needles in this location have higher nutritive value, branches provide sturdy support, and grouse can see approaching avian predators while remaining partially concealed. (Birds of North America, Cornell Lab of Ornithology). (Photo: male Spruce Grouse browsing on Tamarack needles and (inset) looking for grit on the ground.)
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Ruffed Grouse Snow Roosting
I recently had an experience while snowshoeing which I have always hoped to have, but which has escaped me during all these years of tromping through the woods. I was following the tracks of a Ruffed Grouse and all of a sudden it exploded out of the snow about two feet in front of me as it left its night time shelter. Now that we have over ten inches of fluffy snow, grouse can dive into the snow and spend the night in their self-made snow roosts. Finding a grouse’s snow roost is a relatively common experience; being startled by a grouse exiting one is not.
Diving head first into the snow, the grouse works its way anywhere from three to ten feet, creating a 4-inch-wide tunnel through the snow before it hollows out a small cavity and settles down for the night in its own little igloo. Up until recently, a hard crust prevented grouse from seeking shelter this winter in this manner. Had temperatures been very cold, many grouse would have suffered and even perished under these conditions. Fortunately, they can now roost in the snow, where temperatures are much warmer (as high as 32°F.), and rarely fall below 20°F. regardless of how cold it gets outside. Not only do these roosts hide the occupants from predators, but they provide an energy savings of 30 percent or more for grouse.
(Photo: Snow roost entrance hole (nearest the bottom of photo) where a grouse dove into the snow, and the exit hole (nearest top of photo), three feet from entrance hole, which a Ruffed Grouse created when it exploded out of its roost. If you look closely at the exit hole, you may be able to detect wing marks.)
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The Relationship Between Ruffed Grouse & Poplars In Winter
Poplar (also called Aspen) buds are an important winter food source for wildlife, but for none as much as the Ruffed Grouse. During the course of a year, a Ruffed Grouse may feed from as many as 100 species of plants, but in the winter, species of poplar are by far its most important food source. In fact, the relationship between grouse and poplars is such that the range of the Ruffed Grouse is practically identical to the range of Trembling (also known as Quaking) Aspen (Populus tremuloides) and Big-tooth Aspen (Populus grandidentata).
Poplars are dioecious – the male and female flowers grow on separate trees. Although grouse will settle for any poplar bud, it is the male flower buds of Trembling Aspen trees which they prefer, due to the buds’ high amounts of proteins, fats and minerals. (Female buds are smaller and have less nutrients, oddly enough.) Ruffed Grouse seldom feed on a poplar tree that is less than 30 years old. Perhaps these older trees have more vigorous buds, or perhaps their branches are easier to perch on because they are larger. (Information source: Ruffed Grouse: Woodland Drummer by Michael Furtman)
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Ruffed Grouse Drumming
A majority of male passerines, or perching birds (also called songbirds) claim territories and secure mates through song. With the help of a syrinx, or voice box, musical notes, some more complex than others, are created. There are species of birds in different orders that use other parts of their bodies for territorial and courtship displays, among them ruffed grouse (wings), American woodcock (wings) and Wilson’s snipe (tail).
Male ruffed grouse, also known as partridge, are aggressively territorial throughout their adult lives, defending roughly 6-10 acres of woodland which is usually shared with one or two hens. The male grouse claims his property by engaging in a “drumming” display during which he creates a sound reminiscent of a lawn mower starting up. This sound is made by the male beating his wings against the air to create a vacuum, as lightning does when it makes thunder. The drummer usually stands on a log, stone or mound of dirt roughly 10-12 inches above the ground when drumming and this substrate is called a “drumming log.” He does not strike the log to make the noise, he only uses the drumming log as a stage for his display.
Grouse occasionally drum in the summer and fall, but in the spring, drumming becomes more frequent and prolonged as the male advertises his location to hens seeking a mate. This phenomenon is heard but rarely seen by humans; Lang Elliott has captured both the sight and sound of a ruffed grouse drumming in this extraordinary video: http://langelliott.com/mary-holland/ruffed-grouse/ (Sound recording © Lang Elliott – langelliott.com)
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Ruffed Grouse Unable To Seek Refuge in Snow Caves
Unlike much of the Northeast, central Vermont has only a few inches of snow on the ground. These conditions can affect all forms of predators and prey both negatively and positively, from exposed mice and voles to easily-satiated hawks and owls. In the case of Ruffed Grouse, which seek shelter on cold winter nights by diving into the snow, less than 10 inches of snow can spell disaster. In their snow caves they are hidden from view and well insulated (where it rarely drops below 20°F.). A lack of snow can be life-threatening for grouse if the temperature drops too low for too long. Unable to create a sheltered cavity in the snow, Ruffed Grouse bed down on top of it, often close to the base of a tree where there may be some shelter from the wind. Fortunately, most nights have not been extremely cold thus far this winter.
After the grouse departs in the morning, you often find scat where it bedded down. Grouse scat comes in two forms, one a dry, fibrous cylindrical pellet with a white-wash of uric acid at one end, and the other a softer, darker brown plop. The vast majority of a grouse’s diet (buds, twigs, leaves, catkins) goes directly through its digestive system and forms the dry, courser scat. Finer (and more nutritious) material such as the cambium layer of woody plants enters the caeca, two specialized pouches, before passing through the large intestine. The caeca contain bacteria which break down cellulose and produce the more digested, and therefore more liquefied, scat (see foreground in photo).
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Ruffed Grouse Flying Into Windows
Those of us who feed birds are well aware of the hazards that windows and glass doors present to birds. The latest research shows that roughly 988 million birds are killed each year in the United States from hitting windows. Migratory birds and songbirds are the most common victims, but Ruffed Grouse, especially in the fall and winter, are very apt to collide with glass windows. (This phenomenon is not the same as the aggressive behavior towards glass that a bird’s reflection can promote, especially by males during the breeding season.)
Many of the grouse victims are first-year birds. Often, inexperienced young grouse, frightened by a predator, crash into buildings, trees or windows in a so-called “crazy-flight.” Hard, transparent glass is not something grouse recognize as a barrier, due to the reflections it creates. There are a number of things one can do to reduce the chances of this happening. Netting, decals, window film and tape hanging from the top of the window can help. One of many creative new products available are window panes that have external patterns that birds can see from the outside, but that are invisible from the inside. On a national level, legislation and bird-friendly buildings are gaining traction. For more window crash-prevention ideas, go to http://www.birdwatchingdaily.com/featured-stories/15-products-that-prevent-windows-strikes/. (Photo by Eve Bernhard)
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Ruffed Grouse Make Do With Shallow Soft Snow Depth
There are about five or six inches of new powdery snow on top of an icy crust in parts of central Vermont now, with more to come soon. It is common knowledge that ten inches of snow are necessary for Ruffed Grouse to dive into and burrow under the snow in order to make an insulating nocturnal snow roost. With only five inches of snow, a grouse still seeks shelter, but somehow it knows not to dive into the snow from the air. Rather, it lands on the surface of the snow, and then walks along making a groove in the snow as it goes, until it decides to rest for the night.
Several such resting spots were apparent today at the base of trees — slight depressions fully exposed. The grouse that made the snow roost in this photograph shuffled through the snow and then scrunched down without breaking the surface of the snow where it settled for the night, so that it had an inch or two of snow over its body – hiding it from predators, if not providing much insulation. In the morning, after defecating, it departed, not bursting out of a snow bank as it would if there were a lot of snow, but instead lifting off in plain view, leaving faint wing prints on the surface of the snow.
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Ruffed Grouse Nostril Feathers
Ruffed Grouse have adapted to cold winter months in a number of ways, from growing “snowshoe” pectinations on their toes to having their legs covered with fine feathers. Equally effective are the feathers covering a grouse’s nostrils, which are thought to heat cold air as the bird breathes in. (Thanks to Sara and Warren Demont for photo op.)
Ruffed Grouse Preening
Birds have up to 25,000 feathers, and most birds preen, or clean, waterproof and align their feathers, several times a day. Ruffed grouse, as well as most other birds, possess an uropygial gland, or preen gland, on their rump. (Some types of birds, including owls, pigeons, parrots and hawks, lack an uropygial gland and instead have specialized feathers that disintegrate into powder down, which serves the same purpose as preen oil.) The preen gland produces a waxy substance that helps waterproof feathers and keeps them flexible.
Ruffed grouse reach back and rub their beaks on this gland, and then distribute the wax on their body and wing feathers by stroking them toward the tip. The grouse grasps a feather near the base and draws it through the partly close beak, nibbling as it goes. This distributes the wax and cleans parasites from the feathers. In order to preen its head, the grouse must rub it on other parts of its body. Preening is usually done in a fairly open setting but with a degree of overhead protection, so that the grouse can watch for terrestrial predators, while being protected from hawks and owls.
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Ruffed Grouse on Nests
A Ruffed Grouse’s nest is pretty basic – just a shallow bowl on the forest floor, created by the hen grouse tossing leaves over her shoulder and having them fall on her back, slip down to the ground and form a bowl. Ruffed Grouse lay anywhere from 9 to 14 eggs at intervals of 25 to 30 hours, which means it takes about two weeks for a hen to lay an average clutch of 11 eggs. Each of her eggs weighs about 4 percent of her body weight — the entire clutch will be equal to about half of her weight. Once incubation starts (when the last egg is laid) the hen’s behavior goes from wandering around and feeding voraciously, to sitting on the nest and barely moving. Because of this behavior, as well as her cryptic coloration, an incubating Ruffed Grouse hen is much more likely to see you before you see her. She will stay motionless on her nest, even in the face of danger, hiding her eggs. Once she is certain she has been spotted, she will fly off the nest, exposing her eggs. Foxes, crows, ravens, chipmunks, skunks, bobcats and raccoons are some of the predators responsible for the loss of 25% – 40% of grouse nests each year. After the precocial Ruffed Grouse chicks hatch during the first two weeks of June, they will be led away from the nest site by the hen. Within 24 hours they will be feeding on insects and within a week they may double their weight! (Thanks to Ginny Barlow for photo op.)
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Ruffed Grouse Wings
You can often determine the type of flight that a bird is capable of by looking at the shape of its wings. Long, narrow wings are excellent for gliding, while the short, rounded wings of a Ruffed Grouse allow for tight maneuvering in the dense forests where they live. The shape of their wings and their quick-contracting muscles equip grouse for the short bursts of high speed (not long distances) they take when feeding or evading predators. (Photo: a Ruffed Grouse walked a short way and then took flight, beating its wings against the snow twice before it was airborne.)
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Ruffed Grouse Snow Cave
When snow depth is over 10” Ruffed Grouse are known to dive into it and often burrow a short distance in order to seek refuge from the wind and the cold as well as from predators, a behavior known as “snow roosting.” Because the grouse flies into the snow leaving no tracks and little scent, predators have difficulty detecting them. The major risk is freezing rain which can form a crust on top of the snow, trapping the grouse. The Ruffed Grouse’s behavior allows it to conserve a great deal of energy, as the temperature inside this roost rarely falls beneath 20°F. This conservation of energy translates into less time spent up in trees eating buds, exposed to hawks and other predators. When morning comes, the grouse usually bursts out of the snow, leaving a hole and wing marks, or, as in this case, shuffles its way to the surface of the snow before taking off. The presence of scat indicates that the left-hand cavity in this photograph is where the bird bedded down and its exit was made to the right. (Thanks to Edith Hoose for photo op.)
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Staghorn Sumac to the Rescue
They may not be sweet, plump and juicy, but the fruits of staghorn sumac play a crucial role in the lives of many birds that overwinter in New England. True, they’re not a preferred food for these birds, but because they persist through the winter, these fuzzy fruits are an important source of food in late winter and early spring, when very little else is available. Ruffed grouse and wild turkeys rely on sumac fruit as a source of food throughout the winter, and bluebirds, robins, cardinals, mockingbirds and starlings are frequent visitors to staghorn sumac shrubs this time of year.
Ruffed Grouse Roosts and Scat
A trail of ruffed grouse tracks in the snow led me to the spot where two grouse had bedded down for the night behind a fallen tree. With snow too shallow to burrow into, this was as protected a location as they could find. More often than not, a grouse defecates in its night roosting site before leaving in the morning. Grouse scat comes in two forms, one a dry, fibrous cylindrical pellet with a white-wash of uric acid at one end, and the other a softer, darker brown plop. The vast majority of a grouse’s diet (buds, twigs, leaves, catkins) goes directly through its digestive system and forms the dry, courser scat. Finer (and more nutritious) material such as the cambium layer of woody plants enters the caeca, two specialized pouches, before passing through the large intestine. The caeca contain bacteria which break down cellulose and produce the more digested, and therefore more liquefied, scat. Sometimes the two kinds of scat are deposited separately and sometimes, as in the bed on the right in the photograph, together. (Thanks to Dr. Alcott Smith who clarified grouse digestion for me.)
Ruffed Grouse Snow Cave
When the snow on the ground is 10” or more deep, and the night is very cold, ruffed grouse often seek shelter from the elements by diving into the snow and spending the night there. Sometimes they burrow five or ten feet into the snow, but sometimes, as in this case, they stay pretty much where they landed, perhaps a foot or so deep in the snow bank. This adaptive behavior not only hides them from predators, but serves to insulate the bird, as it rarely goes below 20 degrees F. in the cavity, regardless of how cold the air is. More often than not, the grouse defecates during its stay in the snow (dark matter in photograph). When leaving its snow cave, sometimes a grouse will burst out of the snow as it flies away, but as you can see from the groove in the snow in this photograph, this grouse chose to travel by foot.
Ruffed Grouse Winter Adaptations
The Ruffed Grouse has both behavioral and physical strategies for dealing with the cold, snow and ice of New England winters. Three of the physical changes that take place in the fall are evident by looking closely at a grouse’s legs, feet and beak. The feathers on its legs grow thicker and further down towards its feet, to provide better insulation. Small comb-like growths of skin, called pectinations, develop along either side of each toe. These increase the surface area of a grouse’s foot, and serve as snowshoes in deep snow. They also help the grouse cling to icy branches while it quickly snips off poplar and other buds at either end of the day. And on its beak, feathers expand downward to cover its nostrils, slowing the cold air and giving it a chance to warm up before it is inhaled by the grouse.
Ruffed Grouse Crop Contents
Some birds, especially those that eat seeds, buds, leaves and nuts, such as ruffed grouse, eat food very rapidly, faster than it can be passed through the digestive system. These birds usually have a pouch-like crop where food is stored to be digested later, when the birds are not out in the open, susceptible to predators. (see 10-24-12 Naturally Curious post) This rapid consumption and storage of food by grouse, often at dawn and dusk, is referred to as “budding.” Examining the contents of road-killed grouse crops is one way of learning more about this adaptive behavior. Assuming some of my readers might (?) share my curiosity about the diet of grouse, I occasionally post the contents of a grouse crop I’ve recently examined. My most recent dissection revealed that the grouse had switched from its herbaceous summer diet to its more woody winter diet — its crop contained no less than 232 male birch flower buds, or catkins. (Disclaimer: This crop was not that of the grouse that was the subject of the 11-9-12 post.)
Ruffed Grouse & Engines
Ruffed grouse, also known locally as partridge, are so well camouflaged that sometimes the only glimpse you get of them is when they explode right in front of you in an attempt to fly away from you. Occasionally, however, one will allow you more than a cursory look (and an opportunity to photograph it up close). This often happens when someone is running an engine, be it lawn mower, wood splitter or 4-wheeler. Upon hearing the sound, a grouse may walk rapidly towards it and linger in the vicinity for hours. Perhaps the occasional female grouse mistakes the sound of an engine for the alluring drumming of a male grouse, as the drumming sounds uncannily like a lawn mower starting up!
Ruffed Grouse Tracks
For the first time this winter, there is enough snow for ruffed grouse to find shelter from the cold by flying into it and creating a burrow that keeps them relatively warm and invisible to predators. When not resting in their snow burrows on cold nights, or “budding” on nearby aspen buds at dawn and dusk, ruffed grouse do a considerable amount of walking on top of the snow. Their feet are well equipped for this (see Naturally Curious post for 11/4/11) and leave a chain of two-inch, three-toed imprints, one directly in front of the other. (The grouse that left these tracks was walking toward the bottom of the photograph.)
Ruffed Grouse Winter Adaptation
Every fall ruffed grouse grow skin-like fringes called pectinations on either side of each toe. They serve as snowshoes, helping grouse stay on top of the snow when walking, and also help them cling to icy branches while eating the buds of poplars and other trees in the winter. In the spring grouse shed these adaptive fringes. The bird whose foot is in this photograph met its untimely death about a week ago (they frequently fly into windows, as this one did), and I was curious to see the stage of development of the pectinations at this time of year. They appear to be about half to two-thirds the size they will attain when fully developed.
Ruffed Grouse Crop & Gizzard: the initial steps of digestion
Some birds, especially those that eat seeds, buds, leaves and nuts, such as ruffed grouse, eat food very rapidly, faster than it can be passed through the digestive system. These birds usually have a pouch-like crop where food is kept to be digested later, when the birds are not out in the open, susceptible to predators. When the grouse roosts, food leaves the crop and passes through the stomach, which has two parts: a proventriculus – an enlarged area where gastric juices begin breaking down the food, and a ventriculus, or gizzard, which is very muscular, and crushes hard items, such as nuts. According to Roger Pasquier, in Watching Birds, the evolution of an internal means of breaking down food has enabled birds to do away with the heavy teeth and jaws found in fossil birds. Many birds, including grouse, swallow sand or gravel (you’ve probably seen birds on dirt roads doing this) which passes into the gizzard and helps grind up hard food items. One photograph shows the contents of a grouse’s crop – bits of leaves, what I think are huckleberries, barberry fruits, buds and a twig—all intact. If you look closely at the photograph of the gizzard contents, you will see, in addition to crushed fruits and seeds (and two pieces of what appear to be nuts in the upper left) that the grouse recently consumed, tiny bits of sand (upper right) which help in the grinding process.
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