Field Guide to April 2023

Spring-Beauty & the Spring Beauty Miner

By Melory Brandao

Roughly a quarter of Vermont bees are pollen specialists, meaning they have evolved a specific relationship with a few or even a single plant species. Gardening with native plants can turn your home landscape into an oasis for rare bees. One interaction you might see here in Vermont is the Spring Beauty Miner Bee (Adrena erigenae) and two of its host plants. The Virginia Spring-Beauty (Claytonia virginica) is found throughout the Eastern US, while the Carolina Spring-Beauty (Claytonia caroliniana) range is local to the Northeast US and more commonly observed in Vermont. These native woodland flowers are among our earliest blooming flowers in the spring. Growing between March and June, this small plant is a spring ephemeral, meaning it blooms and seeds before the trees in the canopy above leaf out. Spring ephemerals like trout lilies, toothwort, and wild leeks take advantage of the increased sunlight reaching the forest floor early in the growing season. Once the trees above fill with leaves and shade the forest floor, the perennial withers away, leaving only its roots.

Spring ephemerals such as spring beauty are a vital source of pollen and nectar for many pollinators after the cold winter. Although this woodland flower has diverse visitors, the Spring Beauty Mining Bee has a specialized bond to the little pink blossom. This bee is a ground-nesting, solitary species and a pollen specialist, collecting primarily from spring-beauty flowers. These tiny bees have black bodies covered in long white hairs on their heads, thoraxes, and legs. Male bees do not carry pollen and, thus, are smaller and less hairy than female bees, which are often seen covered in the flower’s pink pollen. This will become the sole source of food for her offspring. Each flower on the spring-beauty plant will bloom for three days, but their stamens are active for only one day. And so the female Adrena erigeniae bee must time her pollinating activity carefully.

After collecting a full load of pollen, she forms it into tiny balls to store in her underground brood chamber. After the last collection trip of the day, she returns to her nest and plugs the entrance with soil. In the brood chamber, the bee deposits a single egg on each pollen ball for the larva to feed on when it hatches. The larva pupates during the summer and becomes fully developed by late autumn. Like most solitary bees, the adult bee spends the winter underground and reemerges in the spring along with its faithful flora, the spring-beauty.

You can find this bee and its host plants in woodland habitats with rich, moist soil. Some sightings of the Carolina Spring-Beauty include the Long Trail and Monroe Trail in Camel Hump State Park, the gravel loop road at Downer State Forest, or along the Lake Trail at Red Rocks in Burlington.

If you’re interested in supporting this specialist bee, you can try to cultivate spring-beauties in your garden. The Carolina Spring-Beauty is generally difficult to find for sale, but you can find the Virginia species. You can also propagate the plant yourself by collecting and immediately sowing seeds. Here’s a guide courtesy of the Nomad Seed Project:

Claytonia virginica Seed Collection Guide by the Nomad Seed Project

After pollination, the flowers will begin to fade away sometime in May. The petals will fall off, revealing the seed capsule clasped within the sepals. The capsules will need about a week or two to mature. Once ripened, the capsules will burst open, shooting out their tiny black seeds. Collect the seeds by gathering whole stems of the plant after the seed capsule has turned brown and place them in a paper bag or plastic container. The capsules will explode, and the seeds will be caught inside.

To collect the seeds, gather the whole stems of spring beauty after the spherical seed capsule clasped within the calyx has begun to turn brown (these seed capsules are seen in the photo three pictures above). At this point, around mid- to late May, eruption is imminent, so leave the stems in a bag or a box. As each capsule explodes, the seeds remain caught inside the bag or the box.

In early May, the seed capsules still need about a week or two to ripen and mature. When mature, the capsule splits open, catapulting tiny black seeds in every direction. They can end up two, three, or even four feet from the parent plant—an excellent dispersal tactic.

This woodland flower prefers partial shade in moist, humus soil with good drainage. The plants are spread by tubers and seeds and can be used as a stunning spring ground cover. You can sow seeds outdoors in the spring and expect them to germinate one year later in the following spring. You can also mimic the stratification process by mixing the seed with damp sand in a plastic bag (make sure it’s labeled and sealed), storing it in a warm (about 80°F) location for 60-90 days, and then placing it in the refrigerator for 60-90 days before sowing.

Visit their website for full details and photos!

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Interestingly, there are no images of Claytonia caroliniana seed pods or seeds that this author could find nor a guide specific to its seed collection. One can assume from its similarities that its collection is likely similar to the Virginia species, but I think it’s time the Carolina species gets the attention it deserves. If you happen upon a Carolina Spring-Beauty in bloom, take a picture and post to iNaturalist. Revisit the plant about a week or so later and post more pictures to further document its life stages. If possible, make sure to include in your images the seed capsules that have formed. See if the Nomad Seed Project’s collection method works the same for this species and let us know!

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 signify spring has sprung. Soon, our forests will be filled with singing birds that spend 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 (2,000 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 can fly northward as the warming spring allows. You can track their progress and help VCE determine when they first arrive. As the ice recedes on ponds and lakes, they provide prime breeding habitat for darners. Join our Darner Flight Watch (April 1 – 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.

Synchronized Swimming

By Kent McFarland

On warm, wet nights, when temperatures rise above 40 degrees Fahrenheit and the ground is moist with early spring rain, thousands of Vermont’s amphibians begin their annual march to their breeding pools. The stars of the show are colorful Spotted Salamanders the size of your hand, Wood Frogs that have emerged from their winter deep-freeze, and Spring Peepers preparing to join a deafening chorus of their compatriots. More uncommon, lesser-known species, such as Jefferson’s, Blue-spotted, and Four-toed Salamanders, also move during this time of year.

Male Spotted Salamanders leave their hibernation burrows ahead of the females and arrive first at the pools. They form large balls of wiggling males called congresses. As females arrive, individual males separate from the congress and perform a courtship dance with a female. They circle and put their heads under each other’s tails. The male may climb on her back and rub her with his chin. He then swims away, wiggling his tail. If the female is interested, she will follow him. He leads her to a sperm packet, called a spermatophore, which he deposited earlier on submerged leaves or twigs on the bottom of the pool. She picks up a packet through her cloaca, an opening under the base of the tail used for egg-laying, excreting waste, and egg fertilization. The female may collect packets from several males. She then lays several hundred eggs in small gelatinous balls.

Grab a headlamp and raincoat and witness this magical dance at a vernal pool near you. You can learn where vernal pools might be and report any you find to our vernal pool project.

Woolly Bear Caterpillars Survive Winter with the Best of Them

By Jason Hill

You’re probably not thinking about caterpillars right now. That’s OK—they’re not thinking about you, either. Quite a few of our Noctuoidea moth species (e.g., underwings, tigers, tussocks, and cutworms) overwinter as larvae underneath the snow and leaf litter. You’re likely familiar with at least one of these cold-hardy species, like the Isabella tiger moth (Pyrrharctia Isabella), or “woolly bears,” as these caterpillars are affectionately known. Woolly bears and other freeze-tolerant insects use a suite of strategies to survive the depths of winter. First, it’s warmer in their hibernacula under the leaf litter than above ground, and the mass of the soil reduces extreme temperature swings. Isabella tiger moth larvae and other species also tolerate the freezing of internal body fluids through a process known as supercooling: cooling a liquid below its freezing point without that liquid becoming solid. Woolly bears can supercool to temperatures down to at least -8 ˚C (~17 ˚F) by increasing levels of glycerol (an alcohol and cryoprotectant in this case) and other chemicals in their hemolymph (the moth equivalent to blood).

Below these temperatures, woolly bears can still survive by arresting their life cycle development and reducing their metabolism to conserve energy reserves. Cryoprotectants (e.g., sugars and amino acids) also protect cells and biomembranes against injury at these low temperatures by reducing the amount of freezable water in the body fluids. Producing high concentrations of these cryoprotectants is metabolically expensive but may be necessary for survival. Experiments with woolly bears have found that repeated freeze-thaw cycles, compared to a single prolonged freeze, result in substantially higher mortality by damaging immune cells and tissues in their Malpighian tubules (functionally equivalent to kidneys in insects). These findings have troubling implications when viewed through the lens of climate change. Our New England winter temperatures have risen by more than 3 ˚F over the last 50 years and may rise another 3-5 ˚F by the end of the century; this warming trend would likely substantially increase the number of freeze-thaw cycles we’ll experience through the winter and spring.

For more information, see Layne et al. (1999), Marshall and Sinclair (2011), and the IPCC Sixth Assessment Report on Climate Change.

Bird on a Wire

By Liza Morse

While you are out exploring Vermont’s landscape this month, be sure to scan fence posts, power lines, and the tree line along the edge of fields to catch a glimpse of an American Kestrel. Though kestrels generally begin arriving in Vermont in March, they start nesting in most of their range in April. Vermont birders have historically observed higher abundances of kestrels at greater frequencies in April (according to eBird data), making it a prime time to search for this tiny predator.

The American Kestrel, formerly known as the Sparrow Hawk, is actually not a hawk at all but North America’s smallest falcon. These cute little birds–sized 9 to 12 inches in length–can be found perching on trees, telephone wires, or anything else that gives them an overlook of surrounding fields and scrublands. They are scanning for insects, small rodents, reptiles and amphibians, and occasionally small birds like sparrows (hence the name Sparrow Hawk). A 1976 study published in Science found that, impressively, the American Kestrel can spot a 2-millimeter insect from the top of an 18-meter-high tree!

Sadly, the American Kestrel is in decline in many parts of its range, including in the Northeast. The second Breeding Bird Atlas, published by VCE in 2013, found a 26% decline in kestrels since the previous Atlas. This was primarily attributed to a loss of agricultural areas due to forest succession, development, habitat fragmentation, and loss of cavity trees due to the removal of hedgerows. To learn more about how VCE works with landowners to protect grassland habitat for grassland nesting birds and birds that use grasslands (like the American Kestrel), check out our New England Grassland Ambassadors project. For directions on how to build and mount a kestrel nest box, check out Cornell Lab of Ornithology’s NestWatch page.