Field Guide to January 2021

January is cold and harsh, food is limited, and many of Vermont’s wild species are hunkered down for the winter. However, there is still activity all around us. Here are some of Vermont’s January happenings.

Seemingly Im(possum)ble: Virginia Opossum in January

By Julia Pupko

The Virginia Opossum (Didelphis virginiana) may not receive much fanfare in modern times, but it remains one of my favorite native mammalian species. This little critter is the only opossum (and only marsupial) in North America, joined by the other 70 plus species of opossum that reside in the Western Hemisphere as a whole. January is the beginning of the breeding season for the Virginia Opossum, so let us take a look at some of their unique characteristics and the surprising fact that any are able to survive in Vermont at all.

The breeding season for the Virginia Opossum begins in January and lasts through July, separated into two periods: late January through late March and then mid-May through early July. Females can have two to three litters per year, but usually only have one litter at the northern edges of their range. Like other marsupials, opossum females carry their young in an external abdominal pouch. In addition to having this external pouch, females have two separate, internal uteri. Females are receptive to breeding for 36 hours, and after this period they resume their aggressive, solitary behavior. Young are born 13 days after the female breeds, and must crawl unaided into her pouch. The young, which are about the size of a honeybee, attach to a teet, which then swells, making it essentially impossible for them to detach until they are 50 to 70 days old. At this point, they begin leaving the pouch for short periods of time. Young stay with the mother until they are fully weaned, nearly three months after birth.

Some other unique characteristics of the Virginia Opossum include opposable, clawless thumbs on the back feet; a prehensile tail, which can grasp branches and small objects; and the defense mechanism of  “playing possum” (play dead) when extremely scared. Before this opossum plays dead, it will usually hiss and fluff out its coat. If still threatened, it will become limp and motionless, lying on its side with its mouth open and tongue hanging out. Its heart rate and breathing slow to the point of becoming undetectable, and it sometimes releases a putrid-smelling, green fluid from glands on its rear end to deter predators. This state can last for several hours if deemed necessary by the threatened animal. Unlike Raccoons, Virginia Opossums are highly resistant to rabies.

The Virginia Opossum’s range currently extends north to southern Canada, east to the Atlantic Coast, west to Texas, and south to Florida and into Central America. Additionally, this species was introduced to the West Coast, and can now be found in California, Oregon, and Washington. While the species is a habitat generalist and highly adaptable to human-altered environments, it remains limited by its poor adaptations for surviving winter weather. The Virginia Opossum remains active year-round, and has a very thin coat, with hairless ears and tail. In cold climates, they frequently get frostbite on their extremities, and have high mortality rates during the winter. At the northern reaches of its range, Virginia Opossums are partially aged by the presence or absence of frostbite damage, with signs of frostbite indicating that they have made it through at least one winter. They usually do not live to be two years old in Vermont, while they can live much longer in warmer regions.

Given their poor adaptations for winter and high mortality rate, how do any Virginia Opossums survive in Vermont? One helpful adaptation is their ability to put on a layer of fat before winter, providing a little extra insulation. They remain in their dens on exceptionally cold days as well, for protection from the most bitterly cold temperatures. Additionally, climate change has likely assisted their northward spread. While they were recorded in the Long Island region prior to 1880, it was not until the 1920s that the first Virginia Opossum was recorded near Vermont.

The northern shift of this species has its benefits. Virginia Opossums are omnivores and eat a wide range of foods, including ticks. They consume up to 95 percent of the ticks that they encounter and can eat over 5,000 each season. As a result, they can be a major ecological tick control, which is especially important as tick-borne illness prevalence and overall tick populations continue to rise.

Owl Ask Again – “Hoo” is out There?

By Julia Pupko

Many of Vermont’s bird species are still far away in warmer regions, leaving residents and a few northern migrants, including irruptive species, behind. Vermont’s owl species fall into both of the aforementioned groups, and January is a great time to search for some of these species. Vermont has eight owls, seven of which are residents: Eastern Screech-Owl (Megascops asio), Great Horned Owl (Bubo virginianus), Barred Owl (Strix varia), Long-eared Owl (Asio otus), Short-eared Owl (Asio flammeus), Northern Saw-whet Owl (Aegolius acadicus), and Barn Owl (Tyto alba). The eighth owl species is Vermont’s irruptive winter visitor, aptly named the Snowy Owl (Bubo scandiacus). Additionally, Boreal Owls (Aegolius funereus), Great Gray Owls (Strix nebulosa), and Northern Hawk Owls (Surnia ulula) can occasionally be found in Vermont.

Like many owls species, Long-eared Owls are secretive, hunting at night and roosting in dense foliage during daylight hours, making them especially difficult to find. Additionally, Long-eared Owls are relatively quiet throughout most of the year—January included—saving much of their chatter for their courtship and breeding season. However, you should not entirely write off the chance of finding these owls in January. During the winter months, Long-eared Owls roost in groups of up to 20 individuals during the day. Scour conifer (especially pine) stands with dense branches, checking for two- to three-inch long, elongate owl pellets on the ground. If you find multiple pellets under a conifer tree, or see extensive droppings on the ground or lower tree branches, you may have found a roost site. Long-eared Owls roost near the trunk of the tree, on branches with dense foliage.

If you find yourself strolling through open fields during daylight hours, bring your binoculars! This is a favorite location for Snowy Owls, who conveniently hunt during the daytime. You can find these owls roosting on fence posts, roofs, or standing right on the ground, waiting for a tasty small mammal snack to scurry by. They are very nimble, and will sometimes catch small birds in the air. These magnificent owls nest on tussocks in the tundra, moving south in the winter depending on food availability in the north. Males are almost pure white, while the larger females’ feathers are mottled white and dark brown. With some planning, you can look for both Snowy Owls and Short-eared Owls in one trip. Short-eared Owls hunt in fields and marshes at dusk, delicately swooping around with a flight pattern that resembles that of a large moth, scouring the ground for small mammals. These birds are not common, so it is helpful to check out Vermont eBird to figure out where they have been spotted when planning a trip.

January is not a month that used to come to my mind when thinking about bird courtship in Vermont. Apparently, I did not pass this information along to the Great Horned Owls. These birds are largely non-migratory, remaining at their breeding grounds year-round. Between January and February, Great Horned Owls partake in their courtship rituals, which include preening each other, perching close together, bill stroking, and hooting back and forth to each other. They also begin to nest—one of the earliest nesters in Vermont—using abandoned squirrel, osprey, eagle, or hawk nests; cavities; cliffs; or caves that are 30 to 70 feet above the ground. Females will lay one to four eggs, which will emerge between 30 and 37 days later. The preferred habitat of Great Horned Owls includes dense woodlands (for roosting), with surrounding meadows, fields, or farmland (for hunting). Great Horned Owls have been known to take in orphaned nestlings and mate for multiple years, perhaps for life. During cold January nights, you can hear the mated pairs calling to each other, with males repeating “Hoo, hoo-oo, hoo, hoo” four to five times and females repeating “Hoo, hoo-hoo-hoo, hoo-oo, hoo-oo” six to eight times.

When the Great Horned Owls begin to quiet down, keep your ears peeled! As winter rolls on, other owl species begin their courtship and breeding seasons, meaning that they will begin vocalizing frequently, like Great Horned Owls are this month. February is the start of Barred Owl, Long-eared Owl, and Eastern Screech-Owl courtship, followed by Northern Saw-whet Owl courtship in March. Happy owling!

A Wildcat in Winter

By Julia Pupko

As you wander through the winter wonderland of Vermont in January, you may come across feline tracks that appear to be that of a large house cat. This assessment is not too far off—they would likely be that of the Bobcat (Lynx rufus). Bobcats are medium-sized feline carnivores, with average weights falling between 15 and 25 pounds. Bobcats are sexually dimorphic, meaning that males are typically much larger than females, with some growing to reach 30 to 50 pounds. Vermont is still home to both the Bobcat and the Canada Lynx (Lynx canadensis), a slightly larger cousin of the Bobcat. However, while Bobcats are relatively common (yet elusive), the Canada Lynx is listed as Endangered in Vermont. Colonization of the Northeast initially increased Bobcat populations, as other competitors such as Wolves (Canis lupus) and Mountain Lions (Puma concolor) were extirpated. Bobcat populations then experienced declines throughout the early- to mid-1900s due to fur trade and Bobcat bounties, which were created over fears that they would kill livestock. Following increased protections and cessation of bounty kills in the 1970s, Bobcat populations have recovered across the United States.

Bobcats have a wide range, found from Mexico to the southern parts of Canada, and across the contiguous United States, excluding the majority of Iowa, Illinois, Indiana, Ohio, and Missouri. In contrast, the Canada Lynx’s range is farther north, only overlapping with the Bobcat near the Canadian border. As climate change has progressed, Bobcats have been slowly expanding their range northward. Throughout their range, Bobcats utilize a wide range of habitats to hunt hares, rabbits, and squirrels, along with other small mammals, birds, reptiles, amphibians, fishes, and insects. Their preferred habitat seems to include a mosaic of different plant communities, especially those with cliffs and ledges, often including Black Spruce (Picea mariana) and Northern White-Cedar (Thuja occidentalis) swampy areas and Eastern Hemlock (Tsuga canadensis)-hardwood forests. Bobcats require cliffs, ledges, thickets, hollow logs, and other similar cover for denning and resting, and typically utilize semi-open habitat for hunting. Given their preference for patchy habitat, Bobcats have adapted to human-induced land use changes, which has enabled them to keep their range largely intact.

Unlike the Canada Lynx, which has humorously large feet to assist with movement through the snow, Bobcats are not particularly well-adapted for survival in regions that have harsh winters with extended periods of deep snowpack. Deep snow inhibits movement and speed, and Bobcats remain active throughout the year, meaning that those who live in regions with harsh winter conditions must implement behavioral changes to survive. For example, range size and location may shift, and access to rock piles, underground dens, or caves may be vital for the Bobcat to live to see spring. Hunting behavior also changes. Since much of the Bobcat’s diet is comprised of small mammals, winter conditions reduce access to prey—many small mammals either hibernate or tunnel through the snow.  As a result, White-tailed Deer are an important prey source for Bobcats during the winter in Vermont. They attack winter-weakened fawns or deer sleeping in deer yards, using surprise and winter conditions to compensate for their small size. Bobcats will cache their kills, sometimes burying them in the snow, and will return to the kill until it is almost entirely consumed. When food is scarce, Bobcats will eat carrion and may also frequent bird feeders, hunting the squirrels that have congregated there. Additionally, Bobcats are able to fast when food is limited, increasing their chance of survival. Despite these behavioral changes, severe winters can lead to high Bobcat mortality.

When January comes to a close, begin to listen for yowling Bobcats. Bobcats sometimes begin breeding in February, but usually breed between March and April in Vermont. As the breeding season draws nearer, Bobcats will vocalize with increased frequency, and continue to vocalize regularly throughout the breeding season.

Winter Trees

By Julia Pupko

This may come as a bit of a shock, but January is one of my favorite times to identify deciduous trees. The branches of deciduous trees are leafless, giving one an excellent view of the upper bark. Branches within reach reveal plump buds, waiting for changing spring weather to trigger the emergence of leaves, flowers, and new growth. Each tree species has its own unique combination of bud, bark, and branching structure morphology, all of which can be used to identify the trees without the presence of leaves.

The first thing you should look at when trying to identify deciduous trees in winter is the branching structure. Most deciduous trees in Vermont have an alternate branching structure, meaning that the branches and twigs alternate from one side to the other, splitting off of larger branches one at a time. Maple, ash, dogwood, honeysuckles, and Horse Chestnuts have opposite branching structure, meaning that twigs and smaller branches split off in pairs, one on each side of the branch, directly across from each other. Trees do lose twigs and branches, so look carefully when determining the branching structure, as opposite branching structure can appear to be alternate at first glance.

Next, examine the bark. Does it chip and peel? Remain smooth? Crack into ridges that are tightly bound to the tree? Under the outer bark of the tree (called the epidermis) are many layers, including the xylem (conducts water and nutrients from the roots up the tree), vascular cambium (produces xylem and phloem), and the phloem (conducts sugars from the leaves down to the rest of the tree), among a few other parts. As the tissue under the bark grows, the bark must either keep up with this growth and remain smooth, or will crack and split as it is pushed outward. The way that the bark reacts to the tree’s growth and the way that it changes (or does not change) from the bottom of the trunk to the branches are both useful means of identification. It is important to remember that the bark of each individual tree can look different from others of the same species at first glance. However, general characteristics of the bark will remain consistent among individuals of the same species.

If you can access twigs on the tree, the next step of identification lies with the buds. There are several general categories that buds fall into: imbricate, valvate, or naked. Imbricate buds, such as that of Red Maple (Acer rubrum) pictured above, have multiple overlapping bud scales. Bud scales are modified leaves, which protect the tissues for new growth within them. Imbricate buds can have a few scales, or many scales. Valvate buds have two scales, which do not overlap, and resemble praying hands. These bud scales can be smooth (hairless and flat), striated (has tiny ridges, resembling the small lines on your fingernails), or covered with tricombes (resembles tiny hairs). Naked buds do not have bud scales, such as the Bitternut Hickory (Carya cordiformis) pictured above. Each of these bud types come in many shapes and sizes, differing based on species.

Like buds, the twigs of trees differ by species and can greatly assist in tree identification. When examining the twig, determine whether hair (or pubescence, like a fuzzy coating) is present or absent. If pubescence is absent, determine whether there is a glaucous bloom (light colored, waxy coating) on the twig. Also note whether the twig is sticky or not. Following this, turn your attention to leaf scars. Leaf scars can be found above, below, or surrounding the buds on the sides of the twig, or the lateral buds. This mark shows where the leaves attached to the twig before they fell off. Determine the shape of the leaf scar, along with the location. Noting the location of leaf scars in relation to each other (alternate, opposite, or whorled – surrounding the twig) tells you what the leafing structure of the tree is, and if it is alternate or opposite, it is the same as the tree’s branching structure.

This is not an all-inclusive guide to identifying deciduous trees in the winter, but will get you off to a good start. For more information on twig anatomy, check out this link. For an excellent resource on the identification of different tree species, explore Virginia Tech Dendrology Factsheets.

It Takes Guts to Survive a Boreal Winter

By Kent McFarland

Spruce Grouse eat low fiber foods in summer, mostly fruit and insects. But in winter, they switch to a diet of very high fiber, eating mostly conifer needles. These birds forage at mid-crown level in the trees, where needles are more palatable and higher quality, the branches are larger, and the grouse get a birds-eye view of approaching predators while remaining better concealed in thicker foliage.

Back in the 1960s, biologists B. A. Pendergast and D. A. Boag wondered if this seasonal change in diet was accompanied by structural changes in the Spruce Grouse digestive system. For an entire year they sampled grouse each month in Alberta, Canada to find out. In their 1973 paper, they reported that Spruce Grouse gastrointestinal organs did indeed change with seasonal shifts in diet.

In winter, when the birds ate more and poorer quality food to maintain their mass and energy balance, the gizzard grew by about 75%, and other sections of the digestive tract increased in length by about 40%. Captive birds from the same population that were maintained mostly on poultry feed did not have the same size or degree of seasonal gastrointestinal tract change. Evidently, it takes guts to survive the long, dark winters in the boreal forest.

Lively Lichens

By Julia Pupko

Recently, I was snowshoeing through the woods on a slightly warmer winter day. The snow had settled, still deep from a heavy snowstorm a few days prior. Snow no longer coated the tree trunks and branches, having either fallen to the ground or melted in the warm sun. As I slogged along, I noticed a flash of green out of the corner of my eye. Green? My head snapped around, and I realized that a brilliantly-colored lichen had caught my attention. This made me wonder: could the lichens possibly be active in January?

Lichens are actually two organisms living together in a mutualistic relationship, containing fungi and either algae or cyanobacteria. The fungus makes up the majority of the organism (roughly 90 percent), attaching the lichen to the substrate it is growing on and providing protection from extreme conditions. This allows lichens to live all over the world, covering rocks and other substrates that would otherwise be relatively barren. The fungus portion also gives the lichen its shape and fruiting bodies. The algae or cyanobacteria photosynthesizes, providing both organisms with sugars. Lichens do not have roots, stems, or leaves, and only photosynthesize through the algae living on the surface. Additionally, lichens provide important ecological functions—lichens remove both carbon dioxide and pollutants from the atmosphere, act as an important food source for caribou in the winter, and are used as nesting material by birds like the Ruby-throated Hummingbird.

Lichens can photosynthesize down to -20 degrees C. However, lichens require moisture to photosynthesize, so they are often dormant in winter. This day, however, I imagine that the lichens are very active, as they have been provided with moisture from the melted snow. In Vermont, there are over 500 species of lichens. Keep an eye out for them this January, and tip your hat to these powerful friends.