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Posts tagged “Bonasa umbellus

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

 

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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

1-12-17-ruffed-grouse-aspens-049a2566Poplar (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

3-22-16 ruffed grouse IMG_0778A 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

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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

1-25-16 dead ruffed grouse by Eve BernhardThose 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

snow cave 143There 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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