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Field Guide to February 2024

This month, wildlife and the rest of us here in New England will cross a significant threshold: 10 hours of daylight. You can sense it when you head out in the morning. Northern Cardinals, House Finches, and Black-capped Chickadees are among the birds breaking into song, and Hairy and Downy Woodpeckers are starting to drum. Even though we’ve got lots more winter, at least the sound of spring is in the air. So here’s a Field Guide to February to keep your hopes up all day long.

By Vermont Center for Ecostudies February 15, 2024
Stars circle over the Residencia at Cerro Paranal.
Stars circle over the Residencia at Cerro Paranal.

Leap Year 2024

By Kent McFarland

Since it takes the earth 365 days, 5 hours, and 48 minutes to circle the sun, a leap year with one “extra day” every four years is an adjustment that keeps our calendar in synchrony with the planetary cycle. The good news is you have an extra day to work on your species tally for the year!

2980, , bohemian-waxwing-860x584, Bohemian Waxwing / © Bryan Pfeiffer, , image/jpeg,, 860, 584, Array, Array © Bryan Pfeiffer
Bohemian Waxwing © Bryan Pfeiffer
10046, , rwbl_singing_with_red_epaulet_showing_kpmcfarland-3, A male Red-winged Blackbird sings while showing off its red epaulet. / © K.P. McFarland, , image/jpeg,, 800, 600, Array, Array © Kent McFarland
Red-winged Blackbird © Kent McFarland

Winter Specialties, Early Migrants, and Uncommon Holdovers

By Nathaniel Sharp

From the Northeast Kingdom to the Taconic Mountains, Vermont eBirders have continued to seek out birds and track their sightings across the state this winter. Thanks to the efforts of Vermont’s vast network of birders, we learn a little bit more about the species that call the Green Mountain State home every month. Funnily enough, two of the most unusual birds to visit Vermont this winter were found in suburban cul-de-sacs—not precisely what most people consider ideal bird habitat. The Orange-crowned Warbler that has been frequenting a bird feeder array in Essex is wintering much farther north than others of its kind, although orange-crowns are exceptionally cold-hardy compared to other warblers. An even bigger surprise was the discovery of an Ash-throated Flycatcher in Middlebury at the tail-end of 2023, the first Vermont record for this species! This colorful flycatcher is native to the southwestern US and Mexico but is known to wander into the Northeast occasionally.

Both exciting finds show that birds can turn up just about anywhere. A thrilling rarity or surprising out-of-season species could be right in your backyard, and we thank the many birders across the state who share and report these interesting and unusual finds.

Many cycles influence bird distribution and abundance in winter. Everything from mast crops (acorns, beechnuts, and other cyclically produced foods) to El Niño climate patterns play a part in where and when certain species can be found. A group of birds particularly tied to these ever-shifting cycles are the so-called winter finches, species abundant some years in the state and nearly absent in others. This winter, we have seen an influx of Red Crossbills, a finch species that prefers the seeds of conifers, while other winter finches such as Evening Grosbeaks and Common Redpolls have been reported much more sporadically over the winter months. Another irruptive species with a preference for fruits, the Bohemian Waxwing, has also had a banner year in Vermont, with reports of these colorful northern visitors from across the state.

While the vernal equinox is still far off, birders can enjoy the first signs of spring in the form of Red-winged Blackbirds, Brown-headed Cowbirds, and Turkey Vultures. While these three species are abundant in Vermont during the summer, in February they act as harbingers of the changing seasons. They can also tell us a lot about how birds adapt to changes in their environment. Are your local blackbirds, cowbirds, and vultures arriving earlier than usual this year? Let us know by sharing your sightings with Vermont eBird, and learn more about the arrival dates of any species you’re excited to see by exploring the Bar Charts that help visualize Vermont eBird data.

Mourning Cloak <i>(Nymphalis antiopa)</i> – dorsal and ventral © Bryan Pfeiffer
Mourning Cloak (Nymphalis antiopa) – dorsal and ventral © Bryan Pfeiffer

Feeling Butterflies?

By Kent McFarland

At 5 degrees below zero, butterflies were the last things on my mind as I brushed the fluffy snow from my porch. But as I swept away the last flakes along the railing, I noticed a small, brown sack about the size of a tootsie roll attached to the wood. It was firmly held in place by fine threads. Back inside, with a warm cup of bird-friendly coffee, I identified it as a chrysalis of a Black Swallowtail butterfly. Many Black Swallowtail caterpillars fed on my dill plants in the nearby butterfly garden for most of last summer. It was almost certainly one of them. Incredibly, this chrysalis will remain in place until spring returns, signaling the butterfly to emerge from its winter home and fly away.

All butterflies develop from egg to larva (caterpillar) to pupa (chrysalis) and finally to the winged adult, which we see fluttering around. Each species has evolved a strategy that allows them to successfully pass the winter in one of these four life stages. For example, swallowtails pass the winter in the pupae stage, like the Black Swallowtail I found. Skippers, quick little butterflies whose identification can challenge even avid butterfly enthusiasts, spend the winter as a caterpillar. The beautiful little coppers and blues remain as eggs through the winter. Monarchs glide to more hospitable temperatures in the south. And some, like the Mourning Cloak, hunker down and spend the winter as an adult!

Most temperate-zone butterflies survive New England’s deep snows and frigid temperatures in a stage called winter diapause. Metabolic and respiratory rates are low and slow during diapause. The cold itself is not a direct hazard to the butterflies; however, the formation of ice crystals in body tissue is lethal. To keep from freezing, butterflies reduce the amount of water in their blood (White Admiral caterpillars reduce the amount of water in their body by 30 percent) and thicken it with glycerol, sorbitol, or other antifreeze agents. These chemicals function much like the antifreeze we pour into our car radiators. Mourning Cloaks can withstand temperatures down to minus 80 degrees. But it takes cold weather to trigger them to produce these antifreeze agents. If you put a Mourning Cloak in the freezer on a warm summer day, it will quickly die because it lacks antifreeze.

Some butterfly species produce several generations each summer, with the last generation of the summer entering diapause for the winter. The number of daylight hours and temperature, to a lesser extent, control the onset of diapause. When the summer or fall days reach a certain length, the individual is genetically programmed to begin diapause at a certain time later in the season, either in its current stage or a later stage of its life cycle. Because on any given day of spring or summer there are more hours of sunlight in the northern latitudes than in the more southern areas, butterflies go into diapause earlier the farther north an individual is located to avoid the earlier onset of winter. Viceroy larvae are programmed to enter diapause after the individual receives less than 13 hours of daylight in Maryland, 13.5 hours of daylight in Vermont, and 15 hours in Newfoundland.

Overwintering eggs employ two strategies. Eggs are either laid on the twigs of host plants, where they remain until new leaves develop in the spring and the larvae emerge and feed, or the eggs are laid on the leaf litter at the base of the plant (predominantly leafy plants that are destroyed by frost). There they remain until the plant sprouts in the spring. This difference in strategy is linked to host plant type. Species that feed on herbs place their eggs on the ground, while species that feed on trees or shrubs place them on the woody portions. Some, like the endangered Karner Blue, rely on an insulating blanket of snow to protect them from harsh weather. When there is little snow, eggs can become damaged by dry, cold air.

Adults of overwintering species, such as Mourning Cloak or Milbert’s Tortoiseshell, store fat in their bodies in the fall. Before entering diapause, they find places to hide, such as hollow trees or logs, cracks in rocks, or inside old buildings. In these protected and somewhat insulated hideouts, they enter diapause until spring’s longer and warmer days bring them forth to mate and lay eggs for the next generation. These early spring adults may have tattered and ragged wings from their relatively long life of 8 to 10 months.

To break diapause in the spring, an individual must pass through a long period of cold weather and into a longer daylight period. The cold period must be months long to trigger the end of diapause. If it were shorter, the individual might end diapause during a short warm spell only to be clobbered by the next arctic front.

Beautiful butterflies are still around us despite the snow. Their special adaptations will allow them to emerge during the warm days of spring. I’ll be watching the little Black Swallowtail chrysalis on my porch throughout the winter, and the day it bursts from its case and spreads its wings, I’ll know it is truly time to put the snow shovel away and sharpen the garden spade.

Vermont barn in the snow © Kent McFarland
Vermont barn in the snow © Kent McFarland

Snow into Rain

By Rachel McKimmy

As the climate warms, extreme precipitation events are increasing. In the Northeast, these events are becoming more frequent not only in the summer months but also during the winter, as December’s flooding reminded Vermonters. Climate change is expected to turn snow into rain in the winters to come. In regions like the Northeast, where snow used to cover the ground for most of the winter, this shift has implications not just for people but also for wildlife.

During the winter, animals that hibernate underground are insulated by the snowpack above them, like a blanket, which helps them stay warm and preserve their stores of fat. When the snow melts or precipitation falls as rain, there is no blanket to keep hibernators warm. As a result, animals may burn their fat reserves more quickly and find it harder to make it through the winter when food resources are limited. Fat loss and exposure to the elements increase the risk of starvation, especially for baby animals.

The lack of snow cover may also affect animals such as weasels and snowshoe hares, whose coats turn white in the winter. The transition in fur color from brown to white and white to brown comes from their physiological response to the shortening day length rather than the amount of snow on the ground. The waning hours of daylight trigger a response in the hypothalamus, commonly referred to as the “master gland,” and cause animals to undergo many changes that help them survive the winter, including changes in coat color and thickness. For a long time, northern climate patterns were stable enough that these changes in day length served as an appropriate signal. However, the altered temperature and snowfall patterns related to climate change mean that these animals are now preparing for weather that may arrive much later, if it arrives at all. What was once a beneficial adaptation for blending into the winter landscape is now making these animals more visible to predators.

When rain falls on snow and freezes, the resulting crust can cut wildlife off from the vegetation beneath. Predators hunting prey under the snow, such as Barred Owls hunting rodents, will also be unable to reach their food source if the snow has a hard, impenetrable crust.

These changes in precipitation and snow cover will put selective pressure on species that have evolved in New England’s white winters. As we move toward less familiar and predictable conditions, it will be fascinating to learn whether and how they adapt. For some, what we learn could help secure their future in this region.

14201, , scorpion1-580x400, , , image/jpeg,, 580, 400, Array, Array © Gernot Kunz
Boreus westwoodi © Gernot Kunz
14202, , scorpion2-580x400, , , image/jpeg,, 580, 400, Array, Array © Gernot Kunz
Boreus westwoodi © Gernot Kunz

Snow Scorpionflies

By Spencer Hardy

For most northern insects, winter is all about survival, either tucked away in a protected spot or miles away in a warmer climate (yes, insects from several orders migrate 1, 2). Yet not all insects shun the cold—in fact, Snow Scorpionflies (Family Boreidae) are limited to northern latitudes and most active during the coldest months. These wingless insects can be found crawling over the surface of the snow from November to March. Both adults and larvae eat moss and liverworts, with the larvae active during the summer months. Most of this family’s diversity occurs in the mountains of the Western US. Here in the Northeast, there are only two species, which experts can readily separate. So, the next time you dream of butterflies and other summer insects, take a walk to the nearest moss outcrop to see if you can find one of these bizarre Chionophiles (organisms that thrive in the cold). If you’re lucky enough to find one, refrain from picking it up, as the warmth from your hand may be enough to kill it! Just take a photograph and post it to iNaturalist for identification to species.

Birches in winter Photo from VCE archive
Birches in winter Photo from VCE archive

Paper Birches

By Kent McFarland

With their crisp white bark, paper birches provide a strikingly beautiful contrast to the grays and browns typical among New England’s winter trees. But many people don’t realize that the trunks they’re gazing at could belong to either one of two species of paper birch that grow in northeastern North America—Paper or White Birch (Betula papyrifera) and Heartleaf Paper Birch (B. cordifolia), once considered a variety of White Birch.

Four main characteristics distinguish Heartleaf Paper Birch from White Birch.

– The leaf base is heart-shaped (cordate).
– The leaves themselves are dotted with resin glands.
– The young shoots bearing buds or leaves are not hairy.
– A bronze or pinkish inner bark shows when the outer bark peels (a good field mark in winter!).

You may have noticed the contrasting colors when hiking through mid- to high-elevation Appalachian and northern forests, where Heartleaf Paper Birch occurs.

We know surprisingly little about the exact range of these two species. How low in elevation does Heartleaf Paper Birch grow? How high does White Birch climb into the mountains? Do their ranges overlap in some areas? And how will these species respond to climate change—or have they already? Observers adding records to the Vermont Atlas of Life are helping to map these and many other species. We hope you will add your observations, too. Follow these links to compare the Vermont Heartleaf Paper Birch map with the White Birch map.

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