Muskrat - Ondatra zibethicus
Muskrats are the largest and the most aquatic of the voles in North America. These rodents are not closely related to the beaver, although both mammals have evolved similar physical and behavioural adaptations to their shared environment.
Muskrats do not hibernate. The photo above shows a muscat feeding on the ice at the side of a slough (runoff pond) close to the Elbow River.
Muskrats usually feed within 60 meters of their burrow, which allows a high population density in an optimal environment. The population cycles with peaks every eight to ten years. Mink are common predators and the population of this carnivore tends to track that of the Muskrat.
The skull bones in the photos are likely muskrat. I found the bones in the grass about 20 meters from a runoff pond below my home. The muskrat was likely attacked by a predator either while swimming or while grooming or eating by the edge of the pond. The predator likely carried the muskrat into the tall grass to eat.
The pond is home to muskrats. The average litter ranges from 5 to 9 kits. In the fall of 2008 I counted 9 muskrats in the pond at one time. The large number was likely the result of a successful spring litter. Since then I have never seen more than two at a time. Common local predators include coyote, domestic dog, bobcat, mink, larger raptors, and man.
Reference
Naughton, Donna. The Natural History of Canadian Mammals. U of Toronto Press. 2012.
Black-capped Chickadee - Poecile atricapilla
Black-capped Chickadees are prevalent year round in the Calgary area.
Specialized leg muscles enable these birds to feed upside down while hanging from a perch. They are adept at exploiting resources in difficult situations. Food is stored in caches and used during the winter when resources are meager. During very cold winter days chickadees are able to lower their body temperature (regulated hypothermia) from 42 C to 30 C to conserve energy.
Chickadees will pester predators (mobbing behaviour) that are in their territory.
In autumn the new chickadees leave their parents and join a flock with which they will overwinter. These chickadees will mate the next spring with a member of the flock.
The nest is often a cavity in rotten wood. In my neighborhood, the chickadees favor creating cavities in the exterior of a home. They choose a location under the eaves where they excavate into the soffit where the siding meets the roofline.
References
1. The Atlas of Breeding Birds of Alberta. Federation of Alberta Naturalists. 2007.
2. Baicich PJ, Harrison CJO. Nests, Eggs, and Nestlings of North American Birds. Princeton UP. 2005.
3. Sibley David A. The Sibley Guide to Bird Life & Behavior. Alfred A Knopf, Inc. New York. 2001.
House Finch - Carpodacus mexicanus
House Finches winter in Calgary and are less common during the spring and summer. Purple Finches are usually not present during the winter and return in the spring.
The two species can be difficult to differentiate. The finch below was near the top of a tall spruce tree and without my binoculars I was not able to identify the bird. Fortunately I had my camera and the identification was straightforward once I viewed the image on my computer.
The finch on the spruce branch above is a House Finch,
The red colouration in a House Finch is brightest on the forehead and over the cheeks (malar area). In a Purple Finch the entire head is red.
The upper beak in a House Finch is curved. In a Purple Finch the beak is straighter.
The tail in a House Finch is longer than the tail in a Purple Finch. In flight, the tail notch in a Purple Finch is more distinct.
References
Sibley DA. The Sibley Guide to Birds. Alfred Knopf, New York. 2000.
Canadian Beaver - Castor canadensis
The Canadian Beaver is the second largest rodent in the world.
Good beaver tracks are uncommon because the prints are usually wiped out by either the heavy flat tail or by the tree trunks and branches that the animal drags to the water.
The beaver has five toes on the front and hind feet but only three or four usually register.
The impressions of the large broad nails are visible in the left hind print in the photo below.
The quarter-inch incisors of a beaver can cut down a five-inch willow in three minutes! Beavers strip the bark to access the nutritious inner cambium layer.
The protective wire placed around this aspen was not much of a deterrent for a hungry beaver.
The photo below shows the stumps of numerous aspen cut down last year and dragged into the water for use during construction of a lodge.
Once a beaver starts to cut down trees in a grove, these natural engineers tow the trunks and branches to the water over the same trail. This technique clears the pathway and forms channels with progressively lower resistance to drag, and makes the process faster and more energy efficient. The photo below shows a drag channel over the shore and a typical notch at the edge of the water.
References
Naughton D. The Natural History of Canadian Mammals. UofT Press. 2012.
Rezendes P. Tracking and the Art of Seeing. How to Read Animal Tracks and Signs. Firefly Books Ltd. Willowdale, Ontario. 1999.
When the snow disappeared from the garden in my front yard, the bark at the bottom of my columnar crab apple tree was chewed off.
The crab tree is located in designated garden area that is only a few meters from the driveway of my neighbour. You can see the pebbled pavement in the lower left of the photo above. My neighbour shovels his driveway and he throws the snow up on my lawn. Over this last winter, the snow was piled up about four to five feet high in this area. Moles choose to nest under deeper piles of snow. The grass above is filled with typical Meadow Vole runways through the grass and burrows.
A close up of the gnawed area shows tiny grooves that fit with the size of Meadow Vole incisors. Tiny chips of orange bark are strewn on the ground at the base. The vole chewed through the bark to reach the nutritious rich inner cambium layer. This layer of undifferentiated cells produces the bark.
Meadow Vole scat was piled around the base of the tree. There is enough scat in the photo above to confirm that the tree offered many meals for the animal.
There was another pile of scat on the other side of the tree. This scat has a slightly darker and different colour. Perhaps this poop was from a second vole with a slightly different diet. Another possibility is that the scat was formed by the same vole but during a time when the diet of this vole was otherwise different? Or perhaps this vole ate and digested more of the outer bark?
