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Phenology Report, June 7 2022

Interrupted Fern 2
Photo by iNaturalist user pcartier
Interrupted fern closeup

Reminder: Our Season Watch newsletter launched last week! Subscribe here.

John is back in the studio with our weekly update! He's been tracking our transition from spring into summer and reports that events continue to trend behind schedule. There have been exceptions, such as the arrival of the hummingbirds, blue herons, and orioles (they showed up right on time). The most recent on-time arrivals were butterflies: the monarch butterfly and the Canada tiger swallowtail butterfly. (The Eastern tiger swallowtail is also present in the area; it is slightly larger than the Canada tiger swallowtail and has minor variations in coloring. John says it's impressive enough just to know it's a tiger swallowtail, and I agree! If you want to distinguish them, though, here's a video for you: the relevant section starts at 2:30.) So, if you see a large yellow-and-black butterfly on your lilacs, it's likely a tiger swallowtail.

Canada tiger swallowtail butterfly
Photo by iNaturalist user rangersara
Canada tiger swallowtail butterfly

If it's a big ol' orange-and-black butterfly, it's probably a monarch. John points out that the monarchs you welcome back now are the children of the butterflies you said goodbye to last fall! The butterflies that migrated south in the fall flew down to Mexico, where they spent the winter in trees at a high elevation. The cold weather slows their metabolism and appetite, enabling them to rest through the winter on energy reserves (oh, to be a critter that gets to rest half the year!). In the spring, the monarchs head north again to the southern U.S., where they lay an egg on a milkweed plant. That egg becomes a caterpillar, the caterpillar metamorphoses into a butterfly, and that butterfly flaps its way to you! In the Grand Rapids area, John typically sees his first monarch butterfly around June 1st.

Around the same time, the first tiger swallowtail butterfly emerges. The swallowtails don't make the 2,500-mile trek south: instead, the caterpillars overwinter in their chrysalis and emerge as butterflies in the spring. Despite these vastly different overwintering strategies, the two species appear in near synchrony. In the 40ish years that John Latimer and fellow phenologists Dallas and John Weber have been tracking the butterflies, they have reliably appeared within two or three days of each other: pretty interesting! They're back in the region now, so keep an eye out for them (especially near lilacs).

Other butterflies that caught John's attention last week include the clouded sulphur and mourning cloak butterflies. The clouded sulphurs are about an inch across and bright yellow. They can be found on the edges of fields and in open areas (though John's found them in forests too!). A slight black band may be visible along the wing edge during flight.

Clouded sulphur butterfly
Photo by iNaturalist user andywilson
Clouded sulphur butterfly

In contrast, the mourning cloak butterflies are large and almost entirely black, with only a small cream border on the wing. They emerged early in the spring and are laying eggs now. Soon, we won't see them anymore while the next generation hatches, grows, and metamorphoses. After emerging as a butterfly in late July, they enter aestivation (a period of dormancy in the summer). They will become active in the fall, and we'll see them again! Mourning cloak butterflies overwinter as full adults: they hibernate in hollow trees or woodpiles and emerge in early spring.

That checks butterflies off the list! Let's move on to our friends, the dragonflies. If you live in northern Minnesota (or any area with plenty of water), you know it's been a horrific season for mosquitoes. Well, the tables are about to turn on the little suckers: dragonflies are hatching in huge numbers! Interestingly, dragonflies are the most efficient group of predators on the planet. While a hawk successfully kills 25% of its targeted prey, a dragonfly's success rate is around 95% (read more here). Their appetite is enormous: a single dragonfly can eat over 100 mosquitoes in a single day! For mosquitoes, nowhere is safe: the land and air are patrolled by adult dragonflies, while the larvae patrol the water. For us, that's good news: you can even learn how to build a dragonfly garden in your yard to keep mosquito populations down!

Green Darner emerging
Photo by iNaturalist user Martrich
Common green darner emerging from nymph stage

So far this season, John has spotted American emeralds, spiny baskettails, and lots of green darners. The green darners are "breeding prolifically," and John's cheering them on! He hasn't yet seen the chalk-fronted corporal, though its typical emergence date is around May 31st. John describes the chalk-fronted corporal as a stout dragonfly with a wide, heavy abdomen and two white lines on the front of the thorax behind the eye. They are also distinguished from other dragonflies by habitat. John has found them a mile away from the nearest water (quite a feat in northern Minnesota!). John encourages you to enjoy Minnesota's dragonflies' vibrant colors and motions: they're a beautiful (and voracious) bunch!

While the dragonflies and butterflies add splashes of color to the air, the spring ephemerals beautify the forest floor. We are nearing the end of the season: here's John's list of sightings in the past week!

Many of these flowering events are behind by about 7-14 days. John says that the yellow violet is behind schedule by 16 days, sarsaparilla by nine days, starflower by seven days, bluebead lily by 13 days, lilacs by 12 days, crabapples by 11 days, chokecherries by eight days, pinch cherries by 15 days, and the black ash is leafing out ten days late.
The shrubs are flowering and fruiting. John gives us a handy guide: Canada plum and Juneberries flower first, followed by the pin cherry and the chokecherry. At this stage of the season, the pin cherries are setting fruit, and the chokecherries are the predominant flowering shrub in the Grand Rapids region. To identify chokecherry, look for a stalk covered in flowers about the size of your thumb (it looks kind of like a bottle brush!). The red elderberries have finished blooming and set fruit, so check those out.

Photo by iNaturalist user davidfbird
Chokecherry flower

Over the chokecherries, the trees are flowering too! The red oak and bur oak are just past peak flower. In the tree's new growth, look for 1-2 inch long male flowers (catkins). The female flowers are tiny (you may need a hand lens to see them)!

John wraps up the week with ferns! On his phenology walks, he observed that the ferns are almost fully unfurled. This makes them a bit easier to identify (especially the interrupted fern). The interrupted fern gets its name from the placement of its spore-generating parts (sporophytes), which separate (or interrupt) the top and bottom sections of the fronds.

Interrupted fern
Photo by iNaturalist user billmarkm
Interrupted fern with spent sporophytes

So, look for a beautiful, lime-green frond with some weird, dark-green leaves in the middle that look entirely different from the rest of the plant: that'll be your interrupted fern! Other ferns in the area include lady ferns, cinnamon ferns, ostrich ferns, crested wood ferns, oak ferns, and more: John recommends this book for fern identification!

That does it for this week- enjoy the beautiful weather, watch some dragonflies, and don't forget your sunscreen!

Remember that you can send in your reports, anecdotes, and observations! We would love to hear from you (or your children/grandchildren). Get in touch with me (smitchell@kaxe.org) or John (jlatimer@kaxe.org), or text 'phenology' to 218-326-1234.

For more phenology content, subscribe to our Season Watch newsletter!

As a mail carrier in rural Grand Rapids, Minn., for 35 years, John Latimer put his own stamp on a career that delivered more than letters. Indeed, while driving the hundred-mile round-trip daily route, he passed the time by observing and recording seasonal changes in nature, learning everything he could about the area’s weather, plants and animals, and becoming the go-to guy who could answer customers’ questions about what they were seeing in the environment.
Heidi Holtan has worked at KAXE/KBXE for over 20 years. She currently helms the Morning Show as News and Public Affairs Director. Heidi is a regional correspondent for WDSE/WRPT's Duluth Public Television’s Almanac North. In 2018 Heidi received the “Building Bridges in Media” award from the Islamic Resource Group for her work on KAXE/KBXE hosting conversations about anti-Muslim movements in rural Minnesota.
Sarah Mitchell (she/they) joined the KAXE team in February of 2022. Sarah creates the Season Watch Newsletter, writes segment summaries for the website, and coordinates our Engaging Minnesotans with Phenology project. With a background in wildlife biology, Sarah enjoys learning a little bit about everything, whether it's plants, mushrooms, aquatic invertebrates, or the short-tailed shrew (did you know they can echolocate?).