Old farm and ski slopes
© Kent McFarland
As we move into this chilly month, you may find yourself wondering how wildlife adapts and survives each winter. Cozy up with our Field Guide to December and a warm cup of tea to learn how species face the cold-weather challenges ahead, and what they leave behind in the warmer months for you to find.
By Rachel McKimmy
As you’re walking through the forest this winter on a rare warm and sunny day, you might look up at the leaf-barren branches of trees and spot a flash of emerald green lichen on one of the tree trunks.
Lichens look like small plants, but they are actually two types of organisms, fungi and algae or cyanobacteria, living together in a symbiotic partnership. The fungus makes up most of the lichen’s physical structure, attaching it to bark or rocks. Meanwhile, the algae or cyanobacteria photosynthesize, making sugars for both organisms. While lichens can actively photosynthesize in frigid temperatures, they require moisture. As a result, they are often dormant in winter but quickly bounce back when conditions are moist enough.
Identifying lichens is much more difficult than identifying vascular plants, sometimes requiring chemical analysis to determine the exact species. But there are still some common Vermont lichens you can learn to recognize. Lichens are classified by three common growth forms: foliose, fruticose, and crustose.
Foliose
Foliose lichens are shaped like leaves (foliage) and are loosely attached to rocks or bark.
Tree Lungwort (Lobaria pulmonaria) is a foliose lichen that grows primarily in mature, moist forests. It is bright green and has a leathery, leaf-like appearance.
Smooth Rock Tripe (Umbilicaria mammulata) is a foliose lichen, among the largest species of lichens in the world, and is named after the lining of cows’ stomachs. The smooth upper surface of this lichen is often reddish or grayish brown. It curls upward at the edges, showing a dark underside and looking like bark flaking off of a tree.
Fruticose
Fruticose lichens are like little bushes.
British Soldier Lichen (Cladonia cristatella) is a fruticose, cup lichen with whitish-gray stalks housing bright red bulbs at the top. The white and red make them stand out like “redcoats,” a reference to the uniforms British soldiers wore during the Revolutionary War.
Pink Earth Lichen (Dibaeis baeomyces) is another fruticose, cup lichen that closely resembles British Soldier Lichen, but instead of red bulbs, it has pink bulbs and pink-tinged stalks. It often grows directly on soils rather than on bark or rock.
Crustose
Crustose lichens are like crusts that cling to rocks or bark.
Smokey-eyed Boulder Lichen (Porpidia albocaerulescens) is a crustose lichen that grows commonly on rocks. It looks like a flat patch of grayish or greenish growth, with darker, button-like spots (its spore-producing structures) covering its surface. The buttons are bluish-gray and sport a black outline. If you squint, the button-like spots almost seem like tiny eyes.
Yellow Map Lichen (Rhizocarpon geographicum) is a distinctive crustose lichen that appears as bright yellow patches bordered with dark lines, like an ink-drawn map. This lichen grows on rocks in areas of low air pollution.
Lichens are a reminder that life persists even during the darkest, coldest months of the year. So if you find yourself outside this winter and spot any of these organisms, snap a photo and upload them to the Vermont Atlas of Life on iNaturalist. There are over 9,500 observations of lichens on iNaturalist in Vermont, but less than 2,000 of those are research-grade. If you’d rather stay home and cozy beneath some blankets, you can still help contribute to VCE’s Mission to One Million by helping to verify identifications of lichen species on iNaturalist.
By Allie Radin
If you’ve ever looked up into the trees and noticed silken tents, you have spotted a group of social caterpillars. Vermont has a few species of social caterpillars, such as the Eastern Tent Caterpillar (Malacosoma americanum) and the Fall Webworm (Hyphantria cunea). Ironically, the Forest Tent Caterpillar (Malacosoma disstria), does not make a tent but rather spins a small cocoon on the underside of leaves. But what purpose do these social groupings serve? The primary benefits of hanging out together can be grouped into four categories: shelter, foraging, defense, and thermoregulation.
Tents are made when groups of caterpillars weave silk between plant materials, which protects colonies from the elements and provides them with a space where they can pile together to stay warm throughout the chillier spring and fall days. Caterpillar groups will leave the tent to forage for leaves together, and like ants, they excrete chemical trails to guide others to food sources. If a bird comes searching for a tasty snack, the caterpillars exhibit collective protective measures, such as defensive regurgitation and synchronous head flicking to scare off these potential predators. Those webby hideaways are hiding a truly fascinating world of cooperation and collective actions. While the tents are empty in the winter as pupae are cozy in the leaf litter, you can always crack open a caterpillar guidebook and help ID unknown caterpillars of Vermont on iNaturalist for VCE’s Mission to One Million.
By Megan Massa
Fall has stripped the leaves from trees, revealing the once-secret spots where birds raised their young. Only the sturdiest constructions can last through the winter, as most nests quickly unravel. Without the bird or eggs present, identification of these winter nests can be a challenge, but several key structural features provide clues. The type of structure is the first clue: is it a large platform, a small open cup-shaped nest, or a cavity? Also note what materials it’s made of—different species use mud, woven bark, grass, sticks, leaves, or even strips of plastic.
Possession of bird nests requires a permit, so consider documenting any nests you find with photos and uploading them to iNaturalist to be identified.
A brief overview of winter nests you might see:
For more help identifying winter nests, check out: Naturally Curious with Mary Holland, Northern Woodlands, or pick up a copy of A Guide to Nature in Winter by Donald & Lillian Stokes.
By Julia Pupko
According to a 2021 study by the Gund Institute for the Environment at the University of Vermont, the Green Mountain State has warmed nearly 2˚F in the past 120 years, with winter temperatures increasing 2.5 times faster than the annual average since 1960. With this increase in average temperatures has come more variable temperatures, with temperatures in winter months fluctuating between freezing and above-freezing with greater frequency than they have historically. Additionally, there has been a reduction in snowpack depth and cover consistency. Snowpack accumulation early in the year before the soil fully freezes keeps soil temperatures at or slightly above freezing throughout the winter. While a thick, consistent snowpack keeps the soil at a relatively constant temperature, reductions in snowpack depth and consistency expose the soil to air temperature fluctuations, causing it to freeze and thaw with air temperature changes.
Snowpack changes and increased exposure to freeze-thaw cycles affect, in turn, tree root health. While tree growth is mostly concentrated in the summer months in Vermont, tree roots can remain active in soils at or slightly above freezing. When insulated by a thick, consistent snowpack, tree roots can continue to grow, repair damaged roots, and may help the tree prepare for the coming growth season. On the flip side, a deep freeze can damage fine tree roots in the top layers of the soil and inhibit any growth or repair of roots before spring. This means that trees will have to allocate more resources towards root growth and repair during the growing season to compensate for fine-root loss during the winter, which may add detrimental levels of stress to some trees. One study showed that increased freeze-thaw cycles caused trees to over-compensate their fine root production, reduced their nitrogen uptake, and changed nitrogen cycling in the ecosystem. Multiple freeze-thaw cycles can also increase the risk of trunk crack formation and may cause the tree to begin to bud out early if there is an extended warm period, further injuring the tree when new growth is killed upon the return of below-freezing temperatures.
This is not a full list of all of the implications that climate change, reduced snowpack, and increased freeze-thaw cycles may have on Vermont’s terrestrial ecosystems. Much remains unknown about the full depth of impacts from these factors, or how interactions between them may change our ecosystems.
by Kent McFarland
Have you ever seen pine cones on the end of willow branches? They aren’t really pine cones, they are protective homes for the Pine Cone Willow Gall Midge (Rhabdophaga strobiloides), a type of fly that relies on willows for its home. The adult gall midge lays its egg on the tip of a willow branch as the terminal buds begin to swell in the early spring. The egg, and larva that hatches, release a chemical that tricks the growing willow leaves into forming a structure that looks superficially like a pine cone made of overlapping leaves.
As the larva feeds, the bud ceases to develop; however, the plant still directs nutrients to the tissues. Biologists working at the University of Michigan Biological Station at Pellston, Michigan, found that somehow the gall-midge manipulates the willow to provide resources from other places in the plant to the gall for them to continue to feed and survive. They found that galled twigs compared with normal twigs had greater growth in twig girth than when no gall is present and twigs with galls grew equally well with or without leaves. The bud continues to swell as the larva feeds and grows. When winter sets in, encased in the cone structure, the larva is protected from predators. At some point in the spring, the larva will pupate and the adult gall midge will emerge. They don’t have mouthparts to chew their way out of the gall. Instead, they simply push and squeeze between the overlapping leaves of the gall and fly away.
