Field Guide to April

In April, the northern forest is laid bare with cold desire. 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 remains of autumn to release sweet-onion perfume. Bright white Hepatica opens for wild bees and provides a feast for our eyes. The smell of smoke can fill the air. For a short time before the forest turns green, fires can quickly run through the understory. April leaves none of our senses void. Here’s our guide to some of the joys of April.

Wild for Wildflowers

By Kent McFarland

Spring seems to really “spring” at a slightly different time each year. Sometimes the peepers are calling in late March, other years they remain silent until late in the first week of Spring. The timing of signs of spring, like the blooming of wildflowers and the peeps of spring peepers, can depend on everything from latitude to microclimate. In recent years, a trend towards earlier springs is starting to take shape, and one of the best ways to track these changes is by paying attention to phenology.

Phenology, the study of the timing of natural events such as migration, flowering, leaf-out, or breeding, is key to examining and unraveling the effects of climate change on ecosystems. Assessing the overall trend towards earlier springs involves data collection all across Vermont and beyond. Luckily, this data collection can be as easy as photographing the wildflowers in your backyard! Using your camera or smartphone and the iNaturalist app or website, you can document the time and location of spring ephemeral wildflowers wherever you find them. With the help of the Vermont Atlas of Life on iNaturalist, you can even learn to identify species you haven’t seen before!

Spring ephemeral wildflowers are perennial woodland plants that sprout from the ground early each spring, quickly bloom, and seed before the canopy trees overhead leaf out. Once the forest floor is deep in shade, the leaves wither away leaving just the roots, rhizomes and bulbs underground. It allows them to take advantage of the full sunlight levels reaching the forest floor during early spring. Some spring ephemerals to be on the lookout for this April include Trout Lily, Red Trillium, Bloodroot, and Marsh Marigold.

Long-term flowering records initiated by Henry David Thoreau in 1852 have been used in Massachusetts to monitor phenological changes. Record-breaking spring temperatures in 2010 and 2012 resulted in the earliest flowering times in recorded history for dozens of spring-flowering plants of the eastern United States.

Help Monitor Wildflower Phenology

We have the opportunity to start long-term monitoring across Vermont. Find a plot to monitor in a nearby forest or simply record the status of spring wildflowers you find. You can enter your observations on our site at the Vermont Atlas of Life on Naturalist. Please include a photograph(s) of the plant and select from ‘Flowering’, ‘Fruiting’, or ‘Budding’ in the plant phenology section each observation.

From a Peep to a Cacophony

By Kent McFarland

It’s a warm evening and the only sign of snow are the eroding piles beside the driveway. The spring peepers are in stereo. Down in the valley there is a chorus erupting and up on the hill in a pond another is just beginning to call. Spring has finally sprung.

The cacophony of calling is made up of hundreds of male spring peepers. Each peep call is made by forcing air from their lungs over vocal cords in the larynx and into an air sac in their throat. The air enters the sac from openings on each side of the mouth cavity causing it to balloon outward with air. The inflated sac amplifies and transfers the sound energy from the frog to my ears across the valley.

What sounds like chaos to me, is not to a peeper. Several males may interact vocally by forming duets, trios or quartets, with alternating peep calls and individual pitches. When males alternate calls, one individual, the follower, usually calls within 40 to 70 milliseconds from the end of the leader’s call.

Males tend to stay within an auditory threshold of each other. Spacing and timing of calls accentuates the distinctiveness of each male’s calls so that it is not lost in the din of the chorus and allows a female to zero in on a single calling male. When another calling frog is too close, they may use a second type of call, a trill. The trill seems to reflect a higher degree of aggression than the peep call and may stimulate another individual to move away or to trill back, causing a trill-off. A trill-off can escalate into a brief physical interaction with the winner staying and the loser moving on to quieter waters.

Each male peeper can pump out from 3,000 to 4,000 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 3 percent for the quiet females. Aerobic capacity of trunk muscle is six times that of leg muscles and 17 times greater than female trunk muscle. Peepers derive about 90% of their energy for call production from fat reserves in these muscles. Males weigh on average about the same as two dimes, yet their sound pressure is comparable to the song of a warbler (about 4 quarters in weight) or a blackbird ( a whopping eight half dollars in weight). These little peepers have big bellows.

The peeper mating system is based on female choice. The louder and faster he peeps, the better his chances of attracting a receptive female. When females were presented with recorded peep calls, they preferred peep rates double to those found in the wild. So there is strong sexual selection for males that can peep fast. Because of the strong directional selection for fast calling rates, males perform at or close to their physiological limits. But one night of binge calling doesn’t seem to wear them out. Males that have the higher peep rates in one night tend to have higher peep rates every night.

The evening temperature also affects calling patterns. On warmer evenings peepers call much more frequently. The consumption of oxygen increases with calling rate, which in turn increases with temperature. At a balmy 60 degrees peep calls are repeated up to 13,500 times per night.

All males don’t sing though. The bigger the chorus the more silent males one might find hanging around. These shy guys tend to be smaller than the big singers. They quietly wait near a good singer watching for a female that may be attracted to the peeps. And when she comes along, they use their quickness and agility to beat the singer to the female.

According to the Vermont Amphibian and Reptile Atlas, peepers can begin calling as early as March 15th with peak activity in early May. Chances are good that the spring peeper chorus is now earlier than in the past, according to a study by 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 calls of 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 heard his first peepers on April 4th. Atlas volunteers heard them on average around March 20th, about 13 days earlier.

For us, it is spring music to our ears. For the peepers, it is a singing battle of life and death. I hope their spring tradition goes on and on.

Bird on a Wire

By Liza Morse

While you are social-distance birding this month, be sure to scan fence posts, powerlines, and the tree line along the edge of fields in search of American Kestrels. Though Kestrels generally begin arriving in Vermont in March, they begin nesting in most of their range in April. Vermont birders have historically observed higher abundances of Kestrels and at greater frequencies in the month of April (according to eBird data) making April 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 – sizing up at between 9 and 12 inches in length – can be found perching on trees or telephone wires – anything that will get them a good view – overlooking 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 mm 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 largely attributed to a loss of agricultural areas due to forest succession, development, habitat fragmentation, and loss of cavities due to the removal of hedgerows. To learn more about how VCE is working 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.

Responsible Spring Greens

By Spencer Hardy

The next month is going to present countless challenges, one of which may be access to fresh produce. Unless you have your own greenhouse or a CSA share, we may soon have to decide between a risky shopping trip and going without fresh greens until the summer brings lush gardens and bags of zucchini on the doorstep (hopefully!). 

Luckily the woods, fields, and roadsides around us will be full of greenery in just a few weeks. Many people are familiar with a few wild edibles, namely fiddleheads and ramps (also known as wild leeks). Both of these are widespread in the state, locally abundant, and delicious.

As with any thing you put in your mouth, make sure you know what you are eating – there are plenty of plants and fungi in VT that will make you very sick (or worse). Vermont has at least 26 species of ferns, and only one–the Ostrich Fern (Matteuccia struthiopteris)–is worth eating. A few others are occasionally eaten, but many are hairy and/or contain dangerous toxins. Ramps (Allium tricoccum) also have look-alikes you don’t want to eat. With experience, however both of these are great, safe additions to spring meals.

In these uncertain times it might be tempting to stockpile anything and everything edible you can get your hands on, but please be responsible. Both fiddleheads and ramps are long-lived perennials that can be easily over-harvested, especially in populated areas. Never take more than you can use, avoid harvesting where you suspect others have or will harvest, and make sure that the majority of the patch stays intact. With ramps, cut one leaf per plant and leave the bulb. With fiddleheads only pick a few fiddles per crown. 

There are however, many invasive species that are delicious when prepared right and you can feel good about over-harvesting. Dandelions, Japanese Knotweed, and Garlic Mustard are all widespread, familiar invasives that make great additions to the spring menu. Just be careful not to spread them to new areas–like your compost bin–in the process.

Synchronized Swimming

By Kent McFarland

On warm, wet nights, when temperatures rise above the threshold of 40 degrees 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 are moving 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, he deposited earlier on submerged leaves or twigs on the bottom of the pool. She picks up a packets through her cloaca, an opening under the base of the tail used for egg-laying, excreting waste, and of course egg fertilization. The female may collect packets from several males. She then lays several hundred eggs in small gelatinous balls.

Grab a headlamp and your raincoat and go out 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.

Migrant Dragonflies Arriving at a Pond Near You

By Kent McFarland

A mere three inches long and weighing just four-hundredths of an ounce, it’s sailing on four wings thousands of feet in the air. With little fanfare, it struck northward. This Common Green Darner dragonfly is following spring north and it will likely be the first dragonfly you see this April in the Northeast. Of North America’s over 330 dragonfly species, only a few regularly migrate.

Dragonfly migrations have been observed on every continent except Antarctica, with some species performing spectacular long-distance mass flights. A dragonfly called the Wandering Glider is the long-distance champion, making flights across the Indian Ocean that cover twice the distance of Monarch butterfly migrations.

North America’s most abundant and widespread migrant dragonfly is the Common Green Darner. In the spring, just after the ice has disappeared from the ponds, they suddenly appear, well before any local dragonflies have emerged. They breed soon after arriving, and their nymphs develop quickly in water warmed by the spring and summer sun. Many adults emerge from the ponds in August. They feast on insects to pack on fat, perhaps increasing their weight by up to a third. But instead of breeding at their natal site, they begin a southward migration in autumn that may span a month or even longer.

Migrating only during daylight hours, as far as we know, Green Darners can fly more than 60 miles a day with favorable tailwinds. When the winds turn against them, they stop, sometimes for several days, to dine on mosquitoes, gnats, flies and other insects until the winds urge them onward.

Riding on hot winds from the south, the first Common Green Darners tend to arrive on Vermont ponds as early as mid-April. A few of these dragonflies may have come from as far away as the Yucatan peninsula in Central America or one of the islands in the Caribbean, over 2,000 miles away, while others were perhaps from as close as coastal North Carolina. Their young will take advantage of ample water and prey in the pond and journey back southward before the ponds are locked tight by ice.

Using citizen science data and stable hydrogen isotopes, VCE scientists, along with colleagues at the University of Maryland and Smithsonian Conservation Biology Institute have provided insight into the timing of the Common Green Darner’s migratory cycle. Completed in three generations, the cycle begins in the southern US in February, where one generation begins its migration to northern climes, arriving and mating in spring. A second generation completes the southward migration, and there is even a non-migratory generation that spends its entire life in the southern US, the Caribbean, or in Mexico. To learn more about this fascinating long-distance migration, see VCE’s blog post about this research.

With over 300 million years of evolution behind them, about twice as long as birds, dragonflies have been flying around the globe for a long time. Add your sightings to the Vermont Atlas of Life on iNaturalist and help us track their spring arrival.

Spring Songsters

By Nathaniel Sharp

Last month you may have been lucky enough to hear the muffled songs of hesitant Black-capped Chickadees, Northern Cardinals, or Song Sparrows. These half-hearted chirps and warbles can be heard on the rare warm day of March, but April is when the migration floodgates truly open. Red-winged Blackbirds arrive and conk-a-ree from every melting marsh, and Northern Cardinals and Song Sparrows seem to have gained new confidence in their singing abilities.

You may soon here the charming Peent of the American Woodcock and, if you are lucky, witness the amazing spectacle of its dance. Known by names like “Timberdoodle” and “Bogsucker”, this bizarre looking shorebird spends its early spring days in fields and open lands wet with winter’s melt. Males will choose a displaying territory and participate in elaborate courtship displays involving descents from death-defying heights and musical trilling produced by specialized wing feathers, all in the name of attracting a mate. Join Outdoor Radio and the Mad River Birders on their evening woodcock walk. 

Once trees have budded, but before they have fully leafed-out, you have your best shot at spotting migratory songbirds like warblers, vireos, and the aptly named Ruby-crowned Kinglet in the treetops. Arriving in mid- to late-April, these birds enjoy a buffet of recently emerged insects before settling down into a territory or continuing on their journey north. Submit your bird sightings to Vermont eBird and feel free to include photos and comments of your first robin, warbler, or woodcock of spring! This phenological information, just like blooming times of flowers, can be very useful in tracking shifts in migratory timing of birds in response to climate change.