Two different kinds of signs — droppings and incisor marks – reveal the inhabitants of a woodshed during a very cold spell. The partially-eaten, shelled acorns have tiny grooves in them (difficult to see well in photo, my apologies), made by the incisors of a very small rodent, likely a White-footed Mouse or a Deer Mouse (the animals, much less their signs, are extremely difficult to tell apart, even if both species are sitting in front of you).
The two remaining signs are droppings from birds that sought shelter overnight inside the shed. Mourning Doves have very distinctive scat — individual round droppings, each about 1/4″ in diameter, consisting of coils of dark, solid waste which sometimes have a dollop of white uric acid on top.
The third and last sign is also bird droppings, but unlike the Mourning Dove’s, these are white and log-like. If you’ve been inundated with Dark-eyed Juncos this winter, you should be able to find these on the ground where they congregate.
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It’s fairly unusual to see Deer or White-footed Mice, especially in the winter – they are nocturnal and they spend much of their time in the airspace under the snow next to the ground known as the subnivean layer. (A blanket of snow traps the earth’s heat, which melts the bottom of the snow, creating this layer of space.) Here both Deer Mice and White-footed Mice travel extensively, protected from both the cold (it stays within a degree or two of 32 F. regardless of outside temperature) and the eyes of predators. On cold winter days, groups including both species of mice keep warm by huddling in a common nest. (Photo of White-footed/Deer Mouse – extremely difficult to tell the difference by sight – by Alfred Balch.)
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Deer and White-footed Mice are viewed negatively due to their association with Deer, or Black-legged, Ticks, carriers of Lyme Disease. However, these mice are also beneficial, not only as a staple prey food for many predators, but as a vital contributor to the health of our forests.
Mice help spread various kinds of fungi by eating the fruiting bodies (which contain spores) and eventually excreting the spores. Certain fungi colonize the root system of trees, creating a symbiotic relationship called mycorrhizae. The fungus provides increased water and nutrient absorption capabilities to the tree while the tree provides the fungus with carbohydrates formed from photosynthesis. For many temperate forest trees, these fungi have been shown to be an essential element in order for them to prosper. By consuming fungi and dispersing their spores, these small rodents are inadvertently contributing to the vitality of our forests. (Note: look for the tiny incisor marks of mice in the devoured fungus.)
One of my very favorite animal signs is the winterized home of a Deer or White-footed Mouse. Most songbirds do not re-use their nests. Once the nestlings have fledged, what doesn’t get recycled directly from the nest by other birds or critters slowly disintegrates from rain and snow. That is, unless an agile mouse discovers it and renovates it first. Deer and White-footed Mice are known for using abandoned nests as larders (see https://naturallycuriouswithmaryholland.wordpress.com/2013/10/25/mice-preparing-for-winter/) or as homes for the winter. For the latter, a roof is constructed, usually out of milkweed or cattail fluff, but I have even found man-made insulation used as construction material for a roof. (The pictured nest has been well insulated with a roof of cattail fluff.)
Animals that remain active in New England throughout the year often make preparations for the colder months, when food is much scarcer. Eastern Chipmunks store up to half a bushel of nuts and seeds in their underground tunnels, Red Squirrels hang mushrooms and apples out to dry and White-footed and Deer Mice create larders, often out of abandoned bird nests. Once their young have fledged, most songbirds never re-use their nest. Mice find these empty cup-shaped containers perfect for storing seeds that they collect in the fall. The mouse that took over this Northern Cardinal nest (located in a rose bush) didn’t have to go far to collect a sizeable number of rose hips. One hopes that this isn’t this particular mouse’s only cached food, as most of the seeds (within the fleshy red covering) have been devoured. (Thanks to Marian Marrin for photo op.)
Most songbirds only use their nest once. After their young have fledged, the nest is usually abandoned. In the natural world, recycling has been a way of life for a long time, and abandoned bird nests are not about to be wasted. In the spring, the material used in old nests is often re-used by birds building new nests. But long before this occurs, white-footed mice and deer mice, both of which remain active year round, often use old nests as larders where they store food for the winter. Occasionally they even renovate a nest in the fall in order to make a snug, winter home. They do this by constructing a roof (of milkweed fluff in this photograph) over the nest, which serves to insulate it. Use caution if you come upon such a nest– it could well be inhabited! (Thanks to Sara and Warren Demont for the photo op!)
Mice and voles are commonly lumped together, probably because the differences between them are so slight. Both are small, furry rodents, but mice generally have large eyes, large ears and long tails (close to or greater than the length of their bodies). Voles have smaller eyes, smaller ears (often concealed in their fur), and shorter tails. Voles tend to be active day and night, whereas mice are mainly nocturnal. ( Meadow voles are commonly referred to as “field mice,” which tends to add to the confusion regarding these two groups of mammals!) There are five species of mice in New England (white-footed, deer, house, meadow jumping and woodland jumping), and four species of voles (meadow, southern red-backed, rock and woodland).