Field Guide to August 2020

FEAR NOT— we’ve still got plenty of summer here in Vermont and points north. So in this edition of VCE’s monthly field guide to nature, we’ll celebrate a few audacious summer insects. But we’ll also alert you to animals on the move. Yeah, the “M-word.” So if you’re not quite ready for fall migration, well, sorry… too late.

Mosaic Masterpieces

Nathaniel Sharp

August sits smack dab in the middle of the expected flight schedules of the dragonflies in the genus Aeshna, also known as the Mosaic Darners, brilliantly patterned predators of temperate wetlands. Of Vermont’s 8 known species of Aeshna darners, most begin their transformation from underwater larvae to flying adults in July, and some will continue flying until as late as October.

You can look for these dragonflies—colored with brilliant blues, greens, and blacks in mosaic-like patterns—around lakes, ponds, streams, and other wetlands throughout Vermont. If you’re interested in learning more about the species present in Vermont, such as the aptly-named Lance-tipped Darner, species profiles for all of Vermont’s darners, damselflies, and more can be found on the Vermont Damselfly and Dragonfly Atlas homepage, a project of the Vermont Atlas of Life.

Next time you head outdoors with your bug net or camera/cell phone in tow, you can photograph these agile aerial predators and upload your sightings to the Vermont Atlas of Life on iNaturalist. With clear photos of the top and side views of an Aeshna darner, experts in Vermont and beyond can help you identify which species of darner you’ve found and posted to iNaturalist. Whether you’re watching Canada Darners chasing down mosquitoes and midges in the skies above your local pond, or searching for the first Vermont record of the Subarctic Darner in a far northern spruce bog, these gorgeous insects are certainly worth enjoying as summer winds down towards fall.

Photo: https://www.inaturalist.org/observations/33341264

Honeysuckle Colors Birds

Kent McFarland

Birds don’t always look like they do in the field guides. I was reminded of this just a few days ago while looking at Cedar Waxwings. I noticed that a few of them had tails with orange tips rather than the normal bright yellow.

You are what you eat. These birds assimilated natural pigments called carotenoids from eating berries. These pigments are fat-soluble substances, like vitamin A in carrots from which they take their name. Carotenoids give the characteristic color to pumpkins, carrots, corn, tomatoes, salmon, lobster, shrimp, canaries, flamingos … and the tips of Cedar Waxwing tails.

Orange tails have not been in vogue long. They were first noted about 30 years ago and have become increasingly more common. Orange feathers contain large amounts of the red carotenoid pigment rhodoxanthin that is not found in normal yellow tail tips. The arrival of orange tail tips corresponds closely with the introduction of two invasive honeysuckle shrubs– Morrow’s Honeysuckle and Tartarian Honeysuckle. Both contain large amounts of rhodoxanthin. The ripe red berries are available in July when young waxwings are growing their feathers. Adults don’t molt and grow their feathers until late summer or early fall when the berries are mostly gone, so not many adults have orange tail tips.

It doesn’t just affect waxwings. I have also seen White-throated Sparrows with orange lores rather than yellow and young Veery with red tinted flanks. Eating honeysuckle berries may also account for orange feathers in Yellow-breasted Chat and Kentucky Warblers too. Keep a close watch and share your photos of birds you find with orange where yellow once was the rule.

Photo 1: https://www.inaturalist.org/observations/54868019
Photo 2: https://www.inaturalist.org/observations/836244

Buck Rub

Kent McFarland

For over a month they have been growing up to a quarter inch per day. White-tailed Deer antlers are full grown by mid-August, depending on their age and health. The bucks begin rubbing the velvet off their new antlers in late August. Some believe that you can tell how old a buck is by the size of its antlers. A buck’s antler mass peaks at five to eight years of age, but antler size is also regulated by genetics and nutrition of the individual. The only reliable way to age a deer is by its teeth. Unlike horns on animals like Bison, which are comprised of a bone core covered by a sheath of tough protein called alpha-keratin (same as your fingernails), antlers are just bone and are composed primarily of calcium and phosphorus. Like leaves on trees in the forest, antlers are shed each year.

In Search of a Host

Spencer Hardy

From windshields to Whip-poor-wills, insects face plenty of over-sized dangers—yet many insects are significantly larger than their most formidable foes. An estimated 10% of all described insect species are parasitoids, meaning they develop at the expense of their host, usually eating it alive from the inside out.

As abundant herbivores, bees have become the preferred targets of countless insects in at least 4 orders. With practice, many of these parasites can be found as adults, though one group—the Thick-headed Flies (Conopidae)—are particularly abundant and intriguing. In July and August, any large patch of flowers with abundant bees is likely to be attended by at least one Physocephala. Females of these wasp look-alikes perch and wait for passing bees, which they intercept mid-flight and insert an egg between the abdominal segments as they tumble to the ground. If egg-laying is successful, the parasitoid larvae will develop inside the bee for at least a week, before forcing the bee to bury itself underground, where it dies and the fly pupa overwinters before emerging the next spring.

The vast majority of Thick-headed Flies encountered in Vermont during the dog days of summer are Physocephala furcillata. However, three other species are possible, as are three species of the similar, but less common Physoconops. Identification of both genera is relatively straightforward from clear photos and explained nicely on BugGuide.net.

Photo 1: https://www.inaturalist.org/photos/84442262
Photo 2: https://www.inaturalist.org/photos/86246047

Bird Migration in August?

Kent McFarland

Afraid so. Take Tennessee Warblers, for example. They blast through Vermont in May on their way to boreal forests to breed, and now they’re trickling back through on their southward journey to wintering grounds in northern South America. “Fall” migration can begin for some individuals as early as July. They are gone long before Staghorn Sumacs and Red Maples catch fire and draw busloads of human migrants to Vermont. That’s one of the dirty little secrets about fall migration—it actually begins in summer. To be sure, these Tennessee Warblers are an early “fall” migrant, but it is by no means unusual. If you wait until next month for shorebirds, for example, you will have missed a huge part of their migration. Many have been departing Arctic breeding grounds since mid-July. Be sure to add your bird observations to Vermont eBird, a project of the Vermont Atlas of Life, to help us track their populations.

Photo: https://www.inaturalist.org/observations/28796556

Watching Fast Fritillaries

Kent McFarland

Summer is for fast-flying fritillaries. These orange and black roadsters streak around old fields and meadows halting suddenly to taste the sweet nectar of a flower and then off they go again. Just a few days ago I saw all three species of greater fritillaries found in Vermont in just a few hours of butterfly watching, the treasures of late summer.

Greater Fritillary caterpillars strictly feed on violets. The adults lay eggs on or near the plants and the young larvae hatch and then overwinter in the leaf litter and finish their business the next summer. The adults of all species are mostly orange with black spots, stripes and bars. The undersides have silvery sheens in spots giving them their alternate name of “silverspots”. And for many watchers, they are at first quite difficult to tell apart.

In northern New England we have just three species: Great Spangled Fritillary, Atlantis Fritillary, and Aphrodite Fritillary. There was a  fourth, Regal Fritillary,  found here when New England was a more pastoral landscape. The last one known in Vermont was seen in the 1940s somewhere in Pomfret, Vermont.

It wasn’t long ago that I had a terrible time identifying greater fritillaries in the field, but there are a few tricks here in New England that can help. Fritillaries in the west are a whole different ball game.

The first trick is to get a pair of close focusing binoculars. I have a pair that will focus on my shoelaces. It opens up a whole new world. Many of you are probably bird watchers. Identifying butterflies takes the same skills; the field marks are just smaller! And with digital cameras, we can easily capture what we are seeing to study later and share.

Here’s the key to identifying the greater fritillaries here in New England. Look through those close focusing binoculars and check out their eye color. Yes, that’s right, eye color. One of the three species has gray-blue eyes, the Atlantis Fritillary, like ocean water. The other two have amber or brown eyes. Atlantis also tends to have bold, black wing margins above on both the forewing and hindwing, but remember, this can wear as the butterfly ages.

So now we have two amber-eyed species to sort out. Heck, we’re down to a 50:50 chance now!

Great Spangled tends to be larger, but size is often difficult as a field mark unless the difference is great. In this case, it isn’t that helpful because Aphrodite is also a fairly large butterfly in the east (smaller as you go westward). If you can get a look at the underside of the hindwings, you can usually nail the identification. Aphrodite has a very narrow yellow to cream colored submarginal band (that’s the last cream colored band before the silver spots on the edge of the wing). This band has a lot of brown scaling creeping into it making it very narrow. Great Spangled has a really wide submarginal band. Most, not all, Aphrodite have a beautiful rose blush on the underside of the forewing. The upperside can be a little tricky. Aphrodite Fritillaries have a black spot near the base of the forewing upperside (this is quite small on some Aphrodite specimens, and present on some Great Spangled specimens).

Check out some great field guide photos at the Maritime Butterfly Atlas for each of these species to help you visualize these and other field marks: Great Spangled Fritillary, Aphrodite Fritillary, Atlantis Fritillary.

It sounds hard, but once you begin to look closely, you’ll start to see these fritillaries in a whole new light. Be sure to share all of your butterfly images with our eButterfly project and help us monitor butterflies across the continent.

The Buzz on Northern Dog-day Cicada

Kent McFarland

The dog days of summer are upon us and so is the buzzing sound of the Northern Dog-day Cicada. Males are calling to females with a high-pitched buzz lasting about 15 seconds. It starts softly, gets louder, then tapers off—the only species in this area that sounds like a buzz saw.

These lazy, hot, dog days of August are named for Sirius (the “dog star”) in the constellation Canis Major. Sirius appears in northern skies around the same time that this cicada emerges and starts singing.

Males produce the buzz by using a pair of ribbed membranes, called tymbals, located at the base of their abdomens. A muscle pulls all the tymbal ribs inward. The ribs make a short, sharp noise when they snap inward and outward. The cicada repeats this 300 to 400 times per second to create a the buzz, which can be heard up to a quarter-mile away, and hopefully entice a female. If she’s interested in the song, she snaps her wings. The males hear this and move closer and closer, hoping to eventually mate.

Female cicadas use their ovipositor to saw small gashes into tree twigs, where they lay eggs. After about six weeks the nymphs hatch, drop to the ground, burrow down to a tree root and suck its juices for about three years to maturity. Then one July or August day, Dog-day Cicadas crawl out of the ground and climb up tree trunks as mature nymphs, where they split open and emerge as adults with long wings and bulging eyes—only to live for a few weeks.

Hear cicadas or other insects singing? Make a recording with your smartphone and submit them to the Vermont Atlas of Life iNaturalist project. Its fun and easy!