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Hepatica (Hepatica nobilis) © adege

Field Guide to April 2022

April brings a burst of life to the rugged Vermont landscape. Our long dormant senses awaken. The sweet smell of soil rises to our nose. As the soil warms, Streptomyces bacteria spew chemical weapons against other bacteria, which to us have a distinct earthy smell. Our ears cock skyward at dusk as a Woodcock chatters and twitters across the sky. Spring Peepers burst forth in the evening with up to 4,000 peeps an hour. Blades of wild leeks slice through the soggy, brown autumn remains to release sweet-onion perfume. Bright, white Hepatica opens for wild bees and provides a feast for our eyes. Returning Tree Swallows dance over ponds and marshes. From bees to crayfish, life is on the move. Here’s our guide to some of the joys of April.

By Vermont Center for Ecostudies April 4, 2022
12342, , large, , , image/jpeg,, 1024, 683, Array, Array © K.P. McFarland
Northern Clearwater Crayfish (Faxonius propinquus) - native to Vermont © K.P. McFarland
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Rusty Crayfish (Faxonius rusticus) - non-native to Vermont © K.P. McFarland

Craw-family Time

By Julia Pupko

One of my favorite spring and summer activities involves sloshing down a stream and flipping over rocks to check for occupants. I often head straight for larger, flat rocks—the perfect place to search for Crayfish (Superfamily Astacoidea) and a plethora of other invertebrates. There are around 500 different species of crayfish found across the globe, with about 400 of those species in North America. Vermont is home to three native crayfish species, including the Northern Clearwater Crayfish (Orconectes propinquus), but another five species have been introduced since the 1970s, including the Rusty Crayfish (Orconectes rusticus).

During spring, you may find a female crayfish in “berry,” which means that she is carrying eggs! Her eggs are held under her lower body and tail and resemble a blackberry. While eggs are almost always laid between late April and June (depending on the species), many species mate months earlier in the fall. How do females wait so long to lay eggs?

When crayfish mate, the male transfers sperm to the female’s sperm receptacle, or gonopore. This sperm is stored until conditions are prime for egg-laying (usually sparked by an increase in water temperature in the spring). When the female is ready, she secretes a sticky substance (called glair) onto the underside of her abdomen, tail fan, and swimmerets (small appendages resembling legs on the underside of the tail). The glair acts as glue onto which she releases between 20 and 700 eggs and the stored sperm from the male. Once the eggs hatch, the young cling to the female’s underside for two weeks to four months until they are large enough to venture off on their own. While some species mature in one year, many species cannot reproduce until their second year of life.

If you have ever held a crayfish and weren’t too preoccupied with avoiding its pincers, you have probably noticed that the crayfish is covered in a hardened layer—its exoskeleton. This hardened layer does not allow for growth, so crayfish must shed to grow larger. Young crayfish molt many times a year, but once they reach maturity, their growth slows, and they molt less frequently. Adult females only molt once a year, during the summer, when their young have dispersed. Mature males molt twice a year—once in the summer (Form I) and once in the spring (Form II). These forms are timed around breeding: Form I prepares males for mating in the fall, with chelae (hooks on one pair of legs to grasp females during mating) and hardened gonopods (for transferring sperm to the female). In contrast, Form II males lack these characteristics and appear more like females.

In addition to being eaten by people as a delicacy, crayfish are an essential food source for over 240 wild animals. Some crayfish predators, such as Smallmouth Bass (Micropterus dolomieu), rely nearly exclusively on crayfish for their diet. Crayfish are crucial links in the food chain, eating living and dead plants, invertebrates, and fish.

However, some crayfish species take this role a little too seriously when introduced to new habitats. Remember the non-native Rusty Crayfish I mentioned at the beginning? This species was introduced to Vermont from the western U.S. and can disrupt aquatic environments in areas where it is nonnative. Four inches long with a rusty spot on either side of its body and black-tipped claws, the Rusty Crayfish is slightly larger than our native species and is a vicarious omnivore. They eat unsustainably large amounts of aquatic plants, fish eggs, and even other crayfish. This species outcompetes native crayfish and other invertebrates for food and shelter. And if that isn’t bad enough, the Rusty Crayfish can interbreed with native Northern Clearwater Crayfish—one study in Wisconsin found that the combination of competition and interbreeding allowed the Rusty Crayfish to assimilate an entire lake’s population of Clearwater Crayfish genetically. Eventually, only a quarter of the population had any Clearwater Crayfish genes, and all of the crayfish captured looked just like Rusty Crayfish.

Keep an eye out for crayfish this spring, and be sure to report them to iNaturalist—you can even join the Vermont Crayfish Index Project to help track the distribution of crayfish across the state.

Red-tailed Mining Bee (<i>Andrena erythrogaster</i>) © Spencer Hardy
Red-tailed Mining Bee (Andrena erythrogaster) © Spencer Hardy

April Bees

By Spencer Hardy

Willows (genus Salix) are pollen powerhouses in April. From river banks to roadside ditches, these fast-growing shrubs provide abundant food for early spring pollinators. Their inconspicuous, greenish flowers are visited by a variety of different bees and other insects and are likely the primary pollen source for several specialist bees. These specialist bees are only active for a few weeks in the spring when willows are blooming, from which they frantically gather pollen to provision the next generation that develops over the summer in an underground tunnel. In Vermont, at least eight different species of mining bees (genus Andrena) are thought to be willow specialists, each with slightly different preferences in nesting substrate, climate, and/or willow species. Like most mining bees, they can be tricky to identify from photographs, though several species in this group are quite distinctive. Learn about each species, then go out and see if you can find any in your neighborhood and add them to the Vermont Wild Bee Survey on iNaturalist!

Spring Peeper (<i>Pseudacris crucifer</i>) © Peter Paplanus
Spring Peeper (Pseudacris crucifer) © Peter Paplanus

From a Peep to a Cacophony

By Kent McFarland

It began as just a few peeps down in the valley, but now there’s a chorus erupting. Up on the hill in a pond, another is just beginning. Within a few minutes, the night is filled with Spring Peepers calling from all directions.

The cacophony emanates from hundreds of males. Each peep is made when a frog forces air from its lungs, over the vocal cords in its larynx, and into an air sac in its throat. The air enters the sac from openings on each side of the mouth cavity, causing the sac to balloon outward. The inflated sac acts as a sounding board, amplifying the sound and carrying it from the frog to my ears. What sounds like chaos to me sounds organized to a peeper. Several males may interact vocally by forming duets, trios, or quartets, with alternating peep calls and individual notes. When males alternate calls, one individual, the follower, usually calls within 40 to 70 milliseconds from the end of the leader’s call.

Each male peeper can pump out from three to four thousand peeps an hour for several hours each night. So it is not surprising that male trunk muscles, which help propel air from the lungs, average 15 percent of their body mass compared to only three percent for the quiet females. The aerobic capacity of trunk muscle is six times that of leg muscles and, in males, is 17 times greater than that of female trunk muscle. Males weigh, on average, about the same as two dimes, yet their sound pressure is comparable to the song of a warbler (about four quarters in weight) or a blackbird (a whopping eight half-dollars in weight). These little peepers have big bellows.

According to the Vermont Amphibian and Reptile Atlas, peepers can begin calling as early as March 15, with peak activity in early May. But chances are good that the Spring Peeper chorus around you is now happening earlier than in the past, according to findings by biologists James Gibbs, from the State University of New York in Syracuse, and Alvin Breisch, of the New York Department of Environment Conservation.

From 1900 to 1912, Albert Wright, an instructor in zoology at Cornell University, visited ponds around the campus daily each spring to record the date of the first calling frogs. Ninety years later, volunteers collected the same kind of information for the New York Amphibian and Reptile Atlas, allowing Gibbs and Breisch a chance to compare. Wright, on average, heard his first peepers on April 4. Atlas volunteers heard them around March 20, about 13 days earlier. A nearby study by Gary Lovett from the Cary Institute of Ecosystem Studies found that Spring Peepers initiated calling with a thermal sum with a base of 3°C (37.4° F), which over a 63-year record arrived significantly earlier.

Take a virtual field trip with our biologist and learn more about Spring Peepers, and be sure to record the Spring Peepers near you with the iNaturalist smartphone app and add your observations for science too!

Left Photo: West Virginia White (<i>Pieris virginiensis</i>); Right Photo: Mustard White (<i>Pieris oleracea</i>) © Kent McFarland (left); Bryan Pfeiffer (right)
Left Photo: West Virginia White (Pieris virginiensis); Right Photo: Mustard White (Pieris oleracea) © Kent McFarland (left); Bryan Pfeiffer (right)

A Spring Ephemeral Butterfly: The West Virginia White

By Kent McFarland

It’s not a gaudy butterfly. It isn’t the biggest or the smallest. In fact, it’s mostly just white. But this butterfly is unusual; it only flies in forests. It’s an ephemeral spring wildflower groupie.

To see this butterfly, you need to get to rich, mature hardwoods with spring wildflowers early in the season. Our other, more common veined white, the Mustard White, does fly in woods, but it has distinct dark veins in its first brood (when it may be confused with West Virginia White). The West Virginia White always has faint gray scaling along the veins. And, unlike the Mustard White, it only flies early in the season. Their flight is slow and close to the ground. Follow a woodland stream until you find the host plant—and the butterfly. Its caterpillars only feed on a few plants, mainly Crinkleroot (Cardamine diphylla) and Cut-leaved Toothwort (Cardamine concatenata).

But there’s a dirty player in the field—introduced Garlic Mustard (Alliaria petiolata). Garlic Mustard was first found in the United States in about 1868 on Long Island. Invasions of Garlic Mustard are causing local extirpations of toothwort, and chemicals in Garlic Mustard appear to be toxic to West Virginia White caterpillars, yet the adults are attracted to it and lay eggs on it.

Spring is changing. The snow is melting earlier, wildflowers are blooming sooner, and trees are leafing out faster. How are West Virginia White butterflies faring? Join the West Virginia White Watch (April 1 – June 6) and help us find out!

12348, , large (42), , , image/jpeg,, 1024, 768, Array, Array © K.P. Mcfarland
Common Green Darner (Anax junius) © K.P. Mcfarland
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Common Green Darner (Anax junius) © Josh Lincoln

Dragons On The Move

By Michael T. Hallworth

As the temperature increases across the Northeast, several telltale signs that spring is on its way come into focus. For many, the arrival of Red-winged Blackbirds, Eastern Phoebes, and the chorus of Spring Peepers signifies spring has sprung. Soon, our forests will be filled with singing birds that spent the winter in tropical or subtropical regions. You may already be familiar with their epic journeys north, but did you know a migratory insect is on its way too? The Common Green Darner (Anax junius) migrates long distances—some migrate over 1,200 miles (2000 km) during their multi-generational migration. The first generation is on its way north right now! The first Green Darners will be here any day.

Every flying adult you see early in the season emerged from ponds in the southern United States or the Caribbean. Some aquatic nymphs left behind last year to develop in beaver ponds and lakes in the north won’t mature into adults until late May or early June at the earliest. Read more about how VCE scientists and their colleagues discovered the secrets of Green Darner migration.

Darner migration is closely tied to temperature, and they are able to fly northward as the warming spring allows. You can track their progress northward and help VCE determine when they first arrive. As the ice recedes on ponds and lakes, it provides prime breeding habitat for darners. Join our Darner Flight Watch (March 15 – May 15), and keep an eye out for North America’s largest dragonfly patrolling beaver ponds and lake edges.

Not entirely sure how to identify Green Darners? Check out our guide to key field marks to help distinguish them from other dragonflies. If you see a Common Green Darner, be sure to upload your observations to our iNaturalist project or Odonata Central to help us learn more about how climate change may alter their migration timing and life history.

12256, , large (43), , , image/jpeg,, 1024, 678, Array, Array © Nathaniel Sharp
Knobbedlip Fairy Shrimp (Eubranchipus bundyi) © Nathaniel Sharp
12255, , large (44), , , image/jpeg,, 1024, 678, Array, Array © Nathaniel Sharp
Knobbedlip Fairy Shrimp (Eubranchipus bundyi) © Nathaniel Sharp

Friendly Fairies

By Julia Pupko

Amphibians are not the only Vermont residents who rely on Vernal pools. If you are lucky, you may find a fairy shrimp (Eubranchipus sp.). These tiny crustaceans typically only grow to be three-quarters of an inch and live only for a few short weeks. With no known dispersal mechanism of their own, fairy shrimp are likely inadvertently dispersed by wildlife visiting vernal pools or through flooding events. Fairy shrimp eggs (called cysts) are actually fully developed embryos that sink to the bottom of the pool and enter diapause. They remain in this state until the conditions are just right for hatching, which may explain why some vernal pools have adult fairy shrimp one year but not the next. While the life history of a fairy shrimp may be strange to us, they are remarkably successful, with over 300 species scattered across all seven continents. The oldest known fairy shrimp fossils come from the Cambrian Period—over 500 million years ago!

In New England, at least two species of fairy shrimp are found inhabiting vernal pools. The Vernal Fairy Shrimp (Eubranchipus vernalis) is relatively widespread in southern New England, while further north, it is replaced by the Knob-lipped Fairy Shrimp (E. bundyi). The Knob-lipped Fairy Shrimp is most often seen in early spring, shortly after ice-out. Although little is known about the distribution and abundance of these red-orange fairy shrimp in Vermont and New Hampshire, anecdotal evidence suggests that they prefer larger pools located in relatively undisturbed forest.

Learn more about fairy shrimp at the Vernal Pool Atlas and add your sightings to the Vermont Atlas of Life Project on iNaturalist.

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A Pine Warbler, true to its name in this instance, perches in an Eastern White Pine on a spring morning in Shelburne, VT. © Nathaniel Sharp
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Chipping Sparrows, with a song quite similar to the Pine Warbler's, are also usually some of the first migrants to arrive to Vermont in Spring. © Nathaniel Sharp

Early Arrivals and New Nests

By Nathaniel Sharp

If you’re a birder reading these words in the Maryland-DC Area, New York, Maine, or a handful of other states, you may already be intimately familiar with Breeding Bird Codes, as each of those states is currently conducting a Breeding Bird Atlas. This list of codes—each denoting different observable behaviors that indicate Possible, Probable, or Confirmed breeding of a bird species in an area—is an integral part of any thorough survey of breeding bird activity, and looking for these behaviors is a great way to get to know your local birds even better! Similar to the excitement of seeing or hearing the first phoebe of spring, watching the first American Robin building a nest in your yard, seeing an American Woodcock’s towering display flight, and catching a glimpse of a House Wren with a bill full of food are all signs of the changing seasons.

Paying closer attention to your local birds’ breeding behaviors and adding Breeding Codes to your Vermont eBird checklist can help you witness some exceptional bird behavior while also contributing valuable scientific information on which birds in your area are raising young. Some species like Great Horned Owls and Bald Eagles have already been sitting on their nests for a while now, but new arrivals like Chipping Sparrows, Pine Warblers, and Eastern Phoebes will be settling into territories, setting up nests, and raising young in the coming weeks. When one of your favorite birds seems to be sticking around your yard, see if you can keep a close watch on its behaviors, record it as a Possible, Probable, and (finally) Confirmed breeding bird in your backyard, and add it to Vermont eBird.

Bloodroot (Sanguinaria canadensis) in full April bloom. K.P. McFarland
Bloodroot (Sanguinaria canadensis) in full April bloom. K.P. McFarland

Spring Ephemerals

By Kent McFarland

Spring ephemeral wildflowers are perennial woodland plants that sprout from the ground in early spring, bloom quickly, and seed before the canopy trees overhead fully leaf out. Once the forest floor is deep in shade, the leaves wither away, leaving just the roots, rhizomes, and bulbs underground. This allows the plants to take advantage of the full sunlight reaching the forest floor during early spring.

Many of these plants rely on myrmecochory—seed dispersal by ants. The seeds of spring ephemerals bear fatty external appendages called elaiosomes. Ants harvest and carry them back to their nests and eat them. The unharmed seeds are thrown into the trash bin and eventually germinate. A single ant colony may collect as many as a thousand seeds over a season. Unlike seeds dispersed by birds or wind, a seed is only carried about two meters on average from the parent plant. With such short-distance dispersal, forest fragmentation is a threat to the survival of spring ephemerals. Once these plants are gone from the forest, they rarely return.

Long-term flowering records initiated by Henry David Thoreau in 1852 have been used in Massachusetts to monitor phenological changesPhenology, the study of the timing of natural events such as migration, flowering, leaf-out, or breeding, is key to examining and unraveling climate change’s effects on ecosystems. Record-breaking spring temperatures in 2010 and 2012 resulted in the earliest flowering times in recorded history for dozens of spring-flowering plants in the eastern United States.

You can add new observations to the record books, too, using iNaturalist! Perhaps were he alive today, Henry David Thoreau would be surprised at how many of us are watching and recording flower phenology.

Popular Spring Wildflowers (click to see field guide at iNaturalist)

Trout Lily (Erythronium americanum)
Bloodroot (Sanguinaria canadensis)
Marsh Marigold (Caltha palustris)
Spring Beauty (Claytonia caroliniana)
Red Trillium (Trillium erectum)
Painted Trillium (Trillium undulatum)
Starflower (Trientalis borealis)
Dutchman’s Breeches (Dicentra cucullaria)
Squirrel Corn (Dicentra canadensis)
Jack-in-the-pulpit (Arisaema triphyllum)

Want to help us Make iNaturalist Wildflower Observations More Valuable?

Help us annotate plant records with their flowering status. Visit a species account, like bloodroot, for example, below, and after you learn more about the plant on the page, click the little gear icon and select ‘Add Annotations for Plant Phenology.’

Examine the image(s) carefully and see if there are any plants budding, flowering, or fruiting. If you see any of those, select one of those for Plant Phenology. If there is more than one stage on a single plant, another Plant Phenology will appear, and you can select another stage for the same observation. What if it is bare? If there is no stage of flowering or fruiting, under Observations Fields, type in Flower Phenology and select it from the list. Then add “bare” and click Add. See the example below.

Every annotation will help us better understand how climate change is affecting spring ephemerals in Vermont. Happy flower hunting and annotating!

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