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.)
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.)
We don’t often see millipedes because of their preference for secluded, moist sites where they feed on decaying vegetation and other organic matter. Compost piles, heavily mulched shrub or flower beds, rotting logs, or the soil under logs and stones are likely spots to find these arthropods. Millipedes overwinter as adults, and have been seen migrating in the fall, presumably in search of overwintering sites that will provide them with some protection.
Big Brown Bats, one of the most widespread mammals of North America, are one of the last species of bat to be seen flying in the fall. A relatively hardy species, the Big Brown Bat can tolerate conditions that other bats can’t. However, once cold weather arrives in the late fall and the nighttime temperatures dip down into the 30’s, they go into hibernation.
Both the Big Brown Bat and the endangered Little Brown Bat are considered “house bats,” because they are the most common bats found in houses in both summer and winter. During October, November and December, Big Brown Bats seek out caves, buildings and mines in which to hibernate. Some may migrate short distances to find an appropriate location for hibernating, but many find hibernacula close to their summer residence. Individuals often become active for brief periods during the winter months, sometimes even changing hibernation sites. Big Brown Bats can live up to 18-20 years in the wild but, unfortunately, most Big Brown Bats die during their first winter because they did not store enough fat to survive through their entire hibernation period.
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.)
Black-capped Chickadees actually refresh their brains once a year. According to Cornell’s Laboratory of Ornithology, every autumn Black-capped Chickadees allow brain neurons containing old information to die, replacing them with new neurons so they can adapt to changes in their social flocks and environment.