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Spring in Vermont. © K.P. McFarland

Field Guide to May 2022

Trees are leafing out, and newly arrived migrant birds are dripping from branches. Insects are emerging and pollinating blossoming flowers. Discover all the sights May has to offer with our Field Guide.

By Vermont Center for Ecostudies May 4, 2022
Black-throated Blue Warbler © K.P. McFarland
Black-throated Blue Warbler © K.P. McFarland

Perfectly Timed Leaves: A Sugar Maple’s Story

By Mike Hallworth

Timing is everything, especially if you’re a migratory bird. In the spring, migratory songbirds set their sights on their breeding grounds, and off they go. But only if the conditions are just right.

Many species use environmental cues to determine when to transition between different phases of the year. For example, changes in day length help trigger hormones that send their appetite into overdrive. This hyperphagic state allows them to stockpile fuel measured in muscle and fat for the upcoming migratory marathon. They’ll certainly need it. They fly thousands of miles in just about two weeks—stopping only to rest and refuel before taking to the air the following evening. So there’s no time to waste—arriving at the breeding grounds on time is essential. Delayed arrival by just a few days could be the difference between raising many young or none.

Conditions in New England, when they arrive, play an essential role in the life of these birds. More birds tend to settle into territories at higher elevations in warm springs. Why? Because the trees at higher elevations leaf out earlier in warm springs. Settling at higher elevations comes with risks. The red squirrel, a ravenous nest predator, is more abundant at higher elevations, especially in the transition zone between northern hardwood forest and spruce-fir montane forest. Weather conditions are more variable too, and a late-season cold snap could lead to nest failure, but there is more food. More birds will likely settle into territories at lower elevations in cool springs like this year since the higher elevation areas won’t be as appealing early on.

It turns out that the date of leaf-out is a vital cue that goes beyond selecting a
territory for breeding songbirds. The Black-throated Blue Warbler, for example, uses Sugar Maple leaf-out to help time when to start breeding. Long-term research from Hubbard Brook Experimental Forest in New Hampshire has found breeding pairs’ time egg-laying to coincide with leaf-out. Nesting pairs that lay their eggs as the leaves expand produce more young than those that initiate egg-laying before or after leaf-out.

However, the timing of their cues is changing. As the climate changes, spring leaf-out is occurring earlier and earlier. Sugar Maple leaf-out has occurred 1.6 days earlier per decade on average in New England since they started measuring it at Hubbard Brook. What does that mean for migratory birds? So far, early leaf-out dates could be beneficial for some species. For example, in years when Sugar Maple leaf out is early, Black-throated Blue Warblers are more likely to raise two successful nests in close succession. Conversely, when cool spring temperatures delay leaf-out, fewer pairs can raise two successful nests within a single summer.

Leaf-out © Mike Hallworth
Leaf-out © Mike Hallworth

Help us track changes in Sugar Maple leaf-out and determine how spring temperatures impact Vermont’s plants and animals by submitting your observations to iNaturalist or eBird. Also, be sure to annotate any Sugar Maple observations in iNaturalist using the Plant Phenology field to describe the status of leaf-out and help us track changes through time. Your observations help us understand how climate change affects the plant and animal communities we know and love.

Half-black Bumble Bee <i>(Bombus vagans)</i> © Spencer Hardy
Half-black Bumble Bee (Bombus vagans) © Spencer Hardy

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.

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Juvenile Green Woodpecker (Poland) © Hedera Baltica
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Pileated Woodpecker © Lorie Shaull

Woodpecker Tongues

By Kent McFarland

Stick your tongue out and say, “ahhh.” If you were a woodpecker at your size, your tongue would be hanging nearly two feet out of your mouth. How do they do it?

Our tongues are completely controlled by muscles. A bird’s tongue has small bones sheathed with tissue and muscle the entire length of the tongue. The small bones are collectively called the hyoid apparatus. Woodpeckers have an exceptionally large hyoid apparatus to support a long tongue. Two bones wrap completely around the back of the skull and attach near the base of the upper bill near the nostril to allow the tongue to extend and retract far from the mouth. When they stick their tongue out, they contract muscles that force the hyoid bones forward, propelling it from the mouth.

The Northern Flicker can extend its smooth, pointed tongue up to two inches past the tip of its beak. They also have large salivary glands with sticky saliva. Each time they flick their tongue out, it’s a sticky trap perfect for probing for ants that are a large part of their diet. But not all woodpeckers have long, sharp tongues. The Yellow-bellied Sapsucker has a relatively short tongue with feather-like bristles on the tip. These help it lap up sap via capillary action as it oozes from small rows of holes they drill in tree bark. And the largest woodpecker of them all, the Pileated Woodpecker, has a barbed tip for extracting prey from tree trunks.

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Whirligig Beetle © Erika Mitchell
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Whirligig Beetles © Keith Martin-Smith

Whirling into May with Whirligig Beetles

By Julia Pupko

Standing on a fallen oak tree, partially submerged in the Connecticut River, called Kwanitekw by the Abenaki, I found myself mesmerized by dancing beetles. An entire group of them swirled and twirled across the water’s surface. Individuals periodically paused before resuming their dance or taking it beneath the water’s surface, spiraling into the depths of the water before popping back to the surface on the other side of the log. We call them whirligig beetles (Family Gyrinidae).

As they dance across the water’s surface, whirligig beetles exploit an unusual niche habitat–while many aquatic insects live and hunt at the bottom of rivers, whirligig beetles feast on insects that become stuck on the water’s surface. They even eat mosquito larvae when they come up to breathe. Using a combination of visual cues and vibrations from struggling insects, whirligig beetles hone in on their prey and circle until they can grasp their hapless prey with front legs that are typically tucked against their body.

If you have ever seen whirligig beetles, I imagine you have noticed how quickly they can move when approached. You will also most likely have observed them in groups rather than as individuals on their own. These behaviors are strategic—the rapid spiraling patterns confuse potential predators while living in groups reduces an individual’s risk of getting eaten. However, these are not the only strategies that whirligig beetles utilize. These beetles actually have four eyes, with two positioned above and two below the water’s surface, allowing them to watch for predators on either side. They are also countershaded—dark against the dark background of the water from above and light against the light sky from below. If that isn’t enough protection, the beetles release a noxious chemical when eaten, which stops most predators from trying to eat another whirligig beetle in the future.

There are around 60 species of whirligig beetles found across North America, with at least three species present in Vermont. You can already spot these fascinating beetles dancing across Vermont’s waters. Don’t forget to upload any observations you get to iNaturalist… if you can capture a beetle or even a photo at all!

12429, , large (53), , , image/jpeg, https://vtecostudies.org/wp-content/uploads/2022/05/large-53.jpg, 1024, 683, Array, Array © K.P. McFarland
Twice-stabbed Lady Beetle © K.P. McFarland
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Twice-stabbed Lady Beetle underside view © K.P. McFarland

It’s Ladybug Time!

By Julia Pupko

As soon as the snow has departed from forest floors and there have been a few consecutive days around 50 degrees F, you will likely see tiny black spots trundling along American Beech (Fagus grandifolia) trunks speckled with white fuzz. The white fuzz is actually a tiny insect, the Beech Scale Insect (Cryptococcus fagisuga), which introduces a canker-causing Neonectria fungus, leading to beech bark disease. The mobile black spots are Twice-stabbed Lady Beetles (Chilocorus stigma), a native lady beetle (also called ladybug) known to combat beech bark disease by feasting on Beech Scale Insects.

Other ladybugs soon follow the Twice-stabbed Lady Beetle, emerging from their overwintering sites in the leaf litter, under logs or rocks, or tucked away in other natural nooks and crannies. By May, you can find ladybugs parading across tree trunks, through fields, and on tree and shrub vegetation. As the days become warmer and longer, the ladybugs will become more active, breeding and dispersing across the landscape, searching for large, juicy prey populations (generally aphids, scale insects, and mealybugs). They will then lay their eggs nearby so their young have an available food source to exploit upon hatching.

While the ladybugs carry on their critical ecological roles, we continue to search for missing native lady beetle species, many of whom are declining across their ranges. These declines are likely due to the introduction of non-native ladybug species and land-use change. We hope to wrap up the Vermont Lady Beetle Atlas at the end of this summer, and we need your help to do so. Read our full-length article on missing species and how you can participate here.

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Blackpoll Warbler © K.P. McFarland
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Tennessee Warbler © K.P. McFarland

The Bird Storm

By Julia Pupko

May is here, and migration is in full swing, with birds arriving at their breeding grounds by the bucket-full. The trees are dripping with Yellow-rumped Warblers, Palm Warblers, and Ruby-crowned Kinglets; the shrubs are alive with sparrows; and the skies a coursing mass of swooping Tree Swallows. And more are coming. Near the VCE office, observers have noted multiple sightings of Pine, Black-and-White, and Yellow warblers; Common Yellowthroats; Blue-headed and Warbling Vireos; and Eastern Towhees, to name just a few. Visit the Explore page of Vermont eBird, and filter by your region to see what birds have been sighted near you—and add your checklists too!

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