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Black-throated Blue Warbler singing upon arrival in May. © Kent McFarland

Field Guide to May 2023

The month of May is a show-off. Grass glows green under the deep blue sky. Woodland wildflowers jump out of the ground. Trees flower, and leaves burst from long-dormant buds. Birds arrive on southern night winds and liven the dawn with their chorus. May shouts of life and rejuvenation. Here's your monthly guide to some of this month's delights.

By Vermont Center for Ecostudies May 4, 2023
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Close up of a Chimney Swift head while it is being banded. Kent McFarland
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A banded swift from above showing its long wings and specialized tail feathers. Kent McFarland
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Banded and ready to be released! Kent McFarland

Swift Return

By Kent McFarland

Nothing says spring more than the chattering of Chimney Swifts over town. The swifts circle back and forth, picking out the best chimneys for roosting and nesting. Before European settlement, they likely used giant hollow trees in the forest or shallow caves; some may still. But with the loss of big snags in the forest and the construction of chimneys in the towns and cities, Chimney Swifts transitioned from being country to city dwellers.

Chimney Swifts are perhaps the most aerial of any land bird, only landing when at the nest or roosting at night. They even bathe in flight by skimming the surface with their breast feathers, shaking off water as they fly upward. They do everything in flight, eating, drinking, preening, and even apparently copulating. Their long, sleek wings — much longer than their bodies — help keep them aloft with minimal energy.

Swifts don’t perch like similar-appearing swallows do. You will never see them sitting on an electric line or fence. They have very short legs and long claws to cling to walls of chimneys and other vertical surfaces. The also have tail feathers with long stiff shafts to rest against a wall as they cling, much like woodpeckers.

Annual phenology of Chimney Swift from Vermont eBird.

Annual phenology of Chimney Swift from Vermont eBird.

Recent changes to chimney designs, such as narrow flues and liners, spark arresters and covers, or the outright loss of old chimneys, have decreased available nest sites for swifts and may be a factor in their declining populations. Populations have dropped by nearly 50% in many places throughout the species’ range. Only one pair of Chimney Swifts will nest in each available chimney.

They are gregarious during the non-breeding season. On migration, some old factory stacks may hold thousands of roosting swifts, making these old structures potentially crucial migratory stop-over sites for the birds on their travels to and from their South American wintering grounds.

It is estimated that two parents and their nestlings will consume about 12,000 flying insects daily. Take a walk around your town some evening after dinner to watch the aerial acrobats at work and hear their industrious twittering.

Milbert's Tortoiseshell puddling on a dirt road Kent McFarland
Milbert's Tortoiseshell puddling on a dirt road Kent McFarland

Spring Arrives on Colorful Wings

By Nathaniel Sharp

Now is the time to seek out early spring butterflies as they flutter and glide through hardwood forests, meadows, and bogs across Vermont. This year marks the kickoff of Vermont’s Second Butterfly Atlas, a multi-year project with the aim of better understanding the populations and distributions of Vermont’s butterflies. You can help contribute to this statewide project by spending time in your yard or walking your favorite local trail on a warm, sunny spring day and logging the butterflies you see with eButterfly.

If you haven’t spent much time looking for butterflies before, spring is the perfect time to get started! Many species that are active this time of year are large, colorful, and easy to spot and identify. Maybe you’ve already noticed a gold-edged Mourning Cloak or a stunningly patterned Milbert’s Tortoiseshell, two species that overwinter as adults allowing them first dibs on the first spring flowers. Small and spritely, Azures and Elfins round out the early spring butterfly assemblage, including one species, the Bog Elfin, that has never been recorded in Vermont, though that may change!

Unsurprisingly, Bog Elfins are indeed found in bogs, including several sites in Maine and Massachusetts. Their preference for often inaccessible habitat isn’t the only thing that makes them hard to find. With a short flight window, late May is the only time to have a chance at finding this highly sought-after species. If you visit a nearby bog or make a trip up to Vermont’s Northeast Kingdom in search of Bog Elfin, be aware that rather than visiting flowers, this species is more likely to sit atop the Black Spruce that abound in Vermont’s bogs and fens.

Another butterfly species with a short flight window to look for is the West Virginia White, a Species of Greatest Conservation Need in Vermont that depends on a somewhat little-known spring ephemeral flower. Two-leaved Toothwort isn’t as colorful as a Red Trillium or as showy as a patch of Dutchman’s Breeches, but to a West Virginia White, it’s the ideal food source to kickstart the next generation. Keep an eye out for this species in dense, large patches of toothwort in western Vermont.

Eastern Milksnake JoAnne Russo
Eastern Milksnake JoAnne Russo

Spring Snake Watching

By Nathaniel Sharp

Amphibians like Wood Frogs and Spotted Salamanders run the show in April as they migrate to their vernal breeding pools. However, as temperatures rise and the sun sticks around for a little longer each day, Vermont’s snakes begin to slither onto the stage. Of the 12 species of snakes in Vermont, nine have been documented on the Vermont Atlas of Life on iNaturalist during May.

By far the most numerous and familiar is the Common Garter Snake, which overwinters in underground dens, sometimes gathering in surprisingly large numbers. For the first few warm days of spring, these large groups of green, black, and yellow-striped snakes will hang out and soak up the sun near their den, searching for mates and occasionally creating ‘mating balls’ of multiple males competing for the attention of a single female. Another similarly-striped snake to look for in Vermont is the Eastern Ribbon Snake, a much rarer species often found in fields or open areas near water. This sleek, handsomely patterned snake is striped with black and yellow, much like a Common Garter Snake, but sports white markings on the face and a deep chestnut stripe running along its side.

Two species of snakes that are often mistaken for their venomous counterparts are the Northern Watersnake and the Eastern Milksnake. Boldly patterned with contrasting bands, both these species are nonvenomous and relatively common throughout Vermont, with the Eastern Milksnake often turning up near human habitations. Some of Vermont’s smallest snakes are also making their first appearances in May, including the Dekay’s BrownsnakeRingneck Snake, and the Redbelly Snake, the latter occasionally encountered crossing roads on warm wet nights along with migrating amphibians.

If you’d like to provide a safe haven for these gorgeous hunters of garden pests such as slugs, snails, insects, and rodents, consider setting up a ‘snake hotel’ or a few simple cover boards. Stacking sheets of plywood or flat rocks with some space in between can provide a covered, warm spot for snakes to spend their days and nights. Laying a single sheet of plywood on the ground in a sunny spot, with enough room for snakes to slip underneath, can also provide much-needed shelter.

To learn more about Vermont’s snake species, visit the Vermont Reptile & Amphibian Atlas. If you encounter any of these snakes in the fields and forests of Vermont this May, don’t forget to snap a photo and upload it to the Vermont Atlas of Life on iNaturalist!

Eastern Red Bat roosting while on migration.  Anita Gould
Eastern Red Bat roosting while on migration. Anita Gould

Red Bat Arrival

By Kent McFarland

Eastern Red Bats arrive back in northern New England from the south in May, although little is known about their migration routes or overwintering range. They are strong fliers and are sometimes seen migrating during the day. There have even been reports of the species far offshore during migration. One individual was found 65 miles off the New England coast!

Eastern Red Bats vary in color from brick red to buffy orange. The hairs of the back are tipped with white. Males tend to be less frosted with white than females but are brighter in color. Both sexes have a buffy-white shoulder patch.

Once here, Eastern Red Bats roost by day 30-40 feet high in the foliage of deciduous trees. They select perches that are open from below to permit easy access but are otherwise densely shaded to hide from predators. They hang by one or both feet and resemble a dead leaf.

Eastern Red Bats breed in August and September, but fertilization doesn’t occur until nearly eight months later in spring. A litter of one to five young is born in June or early July, the largest litter size of any bat. Young remain at the roost while their mother forages. Adults feed on many different types of flying insects, but beetles and moths comprise about 50% of their diet. When the mother returns to the roost, the young grasp her with their wings and teeth to nurse. Nursing occurs over about one to two months until the young become independent and disperse.

Schematic of a the olfactory organs used by an Eastern Garter Snake.  Kent McFarland
Schematic of a the olfactory organs used by an Eastern Garter Snake. Kent McFarland

Tasting the Spring Air

By Kent McFarland

When it comes to tongue-wagging, snakes beat even the best gossipers in town. Their tongues seem to flick in, out, and about incessantly as they bask in the spring sun. Like the ears of a gossiper, the snake’s tongue searches for information.

Garter snakes have incredibly colorful tongues – a bright red base and glossy black forked tips. They are also highly sensitive chemical collectors. With each tongue wag, airborne molecules are captured for analysis. Even with its mouth closed, the snake can slide its tongue through a space in its upper jaw.

Inside the mouth, the tongue’s forked tips deliver captured molecules to the vomeronasal organ (VNO), also called the Jacobson’s organ, located in the palate below the nasal cavity. In mammals this organ opens to the nose, but in snakes, it opens to the mouth via small ducts. The tips of the tongue are drawn over narrow grooves in the roof of the mouth, which pass chemical information into the ducts and up to the VNO.

The VNO has two openings in the palate. Its forked tongue may actually allow the snake to have stereo chemo-sensation. If an odor is stronger on one side, the snake can ascertain the direction of the source. The chemo-sensation of the VNO in snakes is much greater than in most mammals. The next time you see a snake, don’t be alarmed by its tongue wagging. It’s just tasting your scent.

Bumble bee visiting a blueberry flower. See Leif Richardson
Bumble bee visiting a blueberry flower. See Leif Richardson

May Bees

By Spencer Hardy

Did you know wild bees make bigger blueberries than domestic bees? Research from UVM has shown that more wild bees lead to bigger, more abundant, and earlier blueberries on commercial farms in Vermont. Since blueberries are native to the Northeast, many native bees are well-adapted to handle the complicated flower morphology. Not only are they a favorite food source of queen bumble bees, but they are also the only food source for roughly six species of specialist bees in New England. Two of these bees are on our “Most Wanted” list of bees not yet recorded in Vermont. If you have a blueberry bush or two in your yard, you have a chance of finding a new species for the state! Don’t forget to share your findings with the Vermont Wild Bee Survey on iNaturalist and add the observation field “Interaction->Visited flower of:” to help us track which flowers bees are visiting.

Comments (1)

  1. Larry Layne says:

    Thanks, for the sterling photos and fascinating info. I think they would inspire many to take a camera when they are out for a walk and then submit their photos to the various Vermont Atlases.

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