Early Spring
Kent McFarland
After a chilly start to spring, warmer weather is finally here. However, that’s hardly the only delight on May’s agenda! Bees buzzing around flowering trees, lively Blackpoll Warblers in backyards, and bud burst await. May is a charismatic month with blockbuster treasures that make it easy for anyone to enjoy the outdoors. For the observant and curious, our field guide (as always) offers ways to get involved, feel connected, and make a difference. Grab your binoculars and take a neighborhood walk — here are the sounds and sights of May.
By Amber Jones
When out looking for insects, our first instinct isn’t always to look up. But in the spring, early-flowering trees are a terrific place to find bees and other pollinators!
Trees and woody shrubs are often overlooked as floral resources for pollinators, but are actually critically important, especially in the spring. Because of the large amount of flowers they provide compared to ornamental gardens and turf plants, they allow bees to expend less energy looking for food, when few other plants are blooming. “When it comes to the sheer amount of resources provided to pollinators in the spring, flowering trees will win out every single time,” says bee taxonomist Zach Portman.
Compared to perennial and annual plants, trees are often underrepresented in studies of plant-pollinator interactions. This means we need more targeted sampling of trees by both professional and community scientists.
There is nothing like walking up to a flowering tree and hearing the tell-tale buzz of hundreds of hungry little bees before you even see them! Look (and listen) for an abundance of early emerging bee species like Andrena (mining bees), Collettes (cellophane bees), and Osmia (mason bees) on your local flowering trees.
By May, maples (Acer spp.) and Serviceberries (Amelanchier spp.) will be done blooming except in more northerly latitudes. Look for these other trees that we’ve noticed are especially attractive to spring bees: hawthorns (Crataegus spp.), cherries (Prunus spp.), apples and crabapples (Malus spp.), blueberries (Vaccinium spp.), and willows (Salix spp.). Some keen observers have also noted that wind-pollinated trees like oaks (Quercus spp.) and birches (Betula spp.) can also attract foraging bees, but we need more information on these uncommon interactions.
When you see bees on trees, snap a picture of the interaction, and upload it to the Pollinators on Plants project in iNaturalist! Perhaps you will even find some of the rarer species that we would love to document like the willow specialist, the Wellesley Miner Bee (Andrena wellesleyana).
By Mike Hallworth
During spring migration, millions of migratory birds make their way north from the tropics and subtropics to the food-rich, temperate, and boreal regions of North America to raise young over just a few short months.
In May, Blackpoll Warblers (Setophaga striata), in particular, seem to descend on Vermont in vast numbers. They are often seen in backyards, foraging in street trees and belting out their high-pitched songs.
This month serves as a fleeting chance for non-birders and non-hikers to see their sleek black cap, yellow feet, and their stunning racing stripe-like streaks down their flanks in their own backyard, before they head on––some to higher elevations of Vermont where the northern hardwood forest and montane spruce-fir zone collide, some much further north to breed in the boreal forest and along the boreal-arctic interface, where the ever-expanding tree line fades away into the Arctic tundra.
Once they arrive at their conifer-rich destination, there’s no time to waste during the short breeding season. Males get straight to work establishing a territory in the hopes of attracting a mate.
Interestingly, where first-time breeders choose to establish territories depends on the progression of spring. In cooler springs like the one we’re having (so far) in 2025, males tend to settle at lower elevations because the delayed leaf-out at their preferred higher elevations means less food is available. In warmer springs when leaf-out happens earlier, males settle at higher elevations. That, however, can come at a cost in later years when they return to the same territory.
That’s because the montane spruce-fir zone on the tops of the higher mountain peaks is home to more than just blackpolls and the iconic Bicknell’s Thrush (Catharus bicknelli). In mast years, when the spruce and fir produce thousands of cones, predators also capitalize on the abundant resources. The American Red Squirrel (Tamiasciurus hudsonicus) moves upslope in response, and the following summer, wreaks havoc on nesting songbirds, preying on both fresh eggs and young nestlings. Blackpoll Warblers are particularly susceptible to this form of predation.
But surviving Red Squirrels and harsh high-elevation environments pales in comparison to what lies ahead for the Blackpoll Warbler during the next phase of its annual cycle.
As fall approaches, the temperatures drop, and the daylight diminishes, Blackpoll Warblers will feverishly forage and put on fat to fuel their upcoming migratory journey. During the peak of breeding season, Blackpoll Warblers weigh about 12 grams on average, about the same as two nickels. By early September, they’ve nearly doubled their weight.
The Blackpoll Warbler is considered one of the ‘confusing fall warblers’ because its autumn plumage is dull enough to confuse this species with other warblers. But its herculean southbound migration over the Atlantic Ocean from the northeastern U.S. to South America makes it stand out in another way. Our past research revealed that Blackpolls fly over the open sea for several days on their way to South America.
This summer we’re embarking on a new tracking study focused on Blackpoll Warblers, this time using the latest tracking technologies available for small birds. If all goes as planned, we’ll learn quite a bit more about these epic Atlantic journeys, including how high they fly and almost exactly how long it takes them to cross the ocean. Hopefully, these data will help shed light on the potential threats they face as they migrate.
That’s enough spoilers, but the (barometric, wink wink) pressure’s on, because Blackpoll Warbler populations are declining at alarming rates.
As you get out and enjoy the spectacle of spring migration, if you encounter a Blackpoll Warbler, be sure to submit your observations to Vermont eBird or iNaturalist so we can track their migration timing. And stay tuned for more news detailing what we discover about one of the longest over-water flights performed by a songbird.
By Ryan Rebozo
As spring progresses, we wait with anticipation for bud break (or bud burst) in deciduous trees and shrubs. Woody plants receive more sunlight and experience warmer spring temperatures, the dormancy of their buds is broken, and new leaves develop and burst out.
Leaves not only signal the arrival of longer and warmer days, they can also reveal hidden pathogens and stressors in trees. Many pathogens and pests afflict trees in New England; look out for these three.
Beech Leaf Disease (BLD)
When a non-native nematode, Litylenchus crenatae ssp. mccannii, infects the dormant buds of American Beech trees, the leaves emerge fully symptomatic—you can identify an infected tree by the dark bands between leaf veins.
As the number of nematodes increases over the summer, infected trees eventually drop their leaves and are forced to regrow new ones. (That’s why you might see a leafless or yellow-leafed tree in the summer.) Newly formed leaves are also susceptible to BLD infection, potentially leading to several leaf-drop events in a single growing season. Over time, the stress of regrowing and losing leaves, coupled with other stressors such as beech bark disease, can kill a beech tree in as little as two years after the initial infection, and at rates as high as 90% in some forests.
American Beech is a significant component of our northern hardwood forests, and unfortunately, BLD mortality has the potential to significantly alter our forest composition.
White Pine Needle Disease (WPND)
Coniferous trees, including the common Eastern White Pine (Pinus strobus), are also susceptible to a number of forest pathogens, including White Pine needle disease. You can see this disease on roadsides and along forest trails, in the yellowing and browning of pine needles. It’s caused by four fungal pathogens: Bifusella linearis, Lecanosticta acicola, Lophophacidium dooksii, and Septorioides strobe.
Infection leads to premature shedding of the browned leaves and a reduced growth rate. This alone is not typically enough to cause white pine mortality, but this chronic stress, when coupled with other stressors, can kill weaker trees.
Because White Pine needle disease is most prevalent when wet springs and early summers are followed by dry late summers and early fall weather, the changing climate is believed to have expanded its presence in the Northeast.
Emerald Ash Borer (EAB)
Some forest pests are initially less obvious. You’ll have to look closely for the small, D-shaped exit holes in ash trees that signal an Emerald Ash Borer (Agrilus planipennis) infestation. This exotic, invasive beetle has spread to more than 35 states, where it has caused significant mortality in ash trees.
While the adults can cause some leaf damage, it’s the S-shaped galleries beneath the bark caused by larval feeding that lead to mortality. These galleries effectively girdle the tree, causing damage around the trunk that prevents the tree from properly transporting nutrients, at which point other signs, such as a thinning canopy and bark flecking (extensive woodpecker damage), signal infestation.
Each of Vermont’s three native ash species, Fraxinus americana (white), F. nigra (black), and F. pennsylvanica (green) is susceptible to EAB. Like the American Beech, ash trees make up an important component of New England forests, and losing them to the Emerald Ash Borer will significantly change the region’s forest composition in the coming years.
If you see signs of tree pathogens or infestations, please report your sighting to Vermont Invasives. And to monitor whether increasing beech or ash mortality will boost woodpecker populations or the numbers of other cavity-nesting species, keep an eye on the Vermont Forest Bird Monitoring Program data dashboard.
