The other day, while staring out at a snowy Gilsland Farm, I wondered to myself “what are Scarlet Tanagers up to right now?” Something about it being ten degrees was making me think of these striking summer residents. Male Scarlet Tanagers (pictured above) look like ripe Roma tomatoes with solid black wings and a whitish, pointy bill. That’s how Mainers know them, at least. Right now in the Southern Hemisphere, determined Colombian birders are craning their necks, trying to tell which species of olive green bird is foraging up in the canopy. If they can get a good look at it, they might discover that it’s a Scarlet Tanager (in Spanish, Piranga Escarlata) in nonbreeding plumage. That name “piranga” is derived from the Tupi word “tijepiranga,” meaning “unknown small bird,” a very handy term for those frustrating back-lit guys in the canopy!
Scarlet Tanagers/Piranga Escarlatas are beloved residents of two places, more if you count all the stops they make along their twice-yearly journey of up to 3,000 miles or more. Phenomena like migration globalized Earth well before our modern economy and the internet connected humans living in different places. Inspired by the Scarlet Tanager, below are a few examples of the many threads that connect Maine to other parts of the planet.
Whales
A chef that I used to work with once set out to make a stew so hearty “you can stand a spoon up in it.” The Gulf of Maine is the hearty stew of the Atlantic Ocean. Gyres formed by the meeting of the Labrador Current and the Gulf Stream, as well as upwelling in places like Georges Bank, bring nutrients from the deep up to the surface. Some animals like Atlantic Puffins exploit it all year round, but others have to scoot when surface temperatures get too cold. Baleen whales like Humpbacks and North Atlantic Right Whales migrate to tropical and subtropical regions in the winter, where they give birth and shed their skin. Shedding skin is probably easier in warmer water, and it’s definitely more comfortable. Those skin cells they slough off, as well as their feces, urine, and milk spilled from lactating mothers, are built from the nutrients they acquired up north in the Gulf of Maine. Any fish or zooplankton that comes across it is in for the feast of its life. It’s estimated that baleen whales bring 46,512 tons of biomass to their wintering grounds every year. There’s a term for this huge movement of nutrients: “the great whale conveyor belt.” These nutrients they bring support food chains in nutrient-poor tropical waters.
Monarchs (Danaus plexippus)
Monarchs are the only butterfly species that make a two-way migration each year. Overwintering Monarchs leave Mexico in the spring and breed in successive generations that hopscotch up the United States, culminating in a “super generation” in late summer that makes the trek all the way back down to Mexico. This is the generation that’s born in Maine. Once they get to Mexico, their habitat is just as specific as it is here, where adults lay eggs exclusively on milkweed plants. Instead of planting milkweed, however, Mexican scientists and butterfly-lovers are racing to save Oyamel fir trees (Abies religiosa).
For the same reason you might see a chilly songbird tucked into the bough of a hemlock, Monarchs overwinter in dense Oyamel fir stands where they’re protected from cold and rain. The microclimate of these forests stays relatively stable, even as temperatures fluctuate throughout the day. As I’m writing this, it’s 65º at the Monarch Butterfly Biosphere Reserve in Michoacán, Mexico, but overnight it’s forecasted to get down to 42º. That temperature change will be much less drastic in a crowded Oyamel fir tree. Monarchs pack themselves onto the boughs and against the trunks (survival is highest on the trunks, which retain more heat because of their mass).
That consistency is what the butterflies are after. Adult monarchs overwinter in a state of diapause (dormancy). If the temperature is too warm, their metabolism will stay too high and they’ll use up their fat reserves at a time when there’s nothing to replenish them with. If it’s too cold, they could freeze, (or, we’re learning, they could come out of diapause early, therefore using too much energy and producing eggs too soon).
Oyamel firs grow in the cool, high-elevation forests of the Trans-Mexican Volcanic Belt. The microhabitat they create is exactly the temperature and moisture level that the butterflies need for a successful diapause. As the climate warms, advocates for this ecosystem are planting Oyamel firs at higher altitudes, which are projected to be cool and moist enough for the trees in 2030, when the altitudes at which they currently grow will likely be too warm and dry. Saving these forests is critical to saving this important North American pollinator.
The Appalachian Mountains
There’s something compelling about the idea of a supercontinent; what if all the land on Earth was just smushed together? Pangea was the most recent one, forming around 250 million years ago, but supercontinents have come together and subsequently broken apart six other times in Earth’s 4.5 billion-year history. Pangea is particularly satisfying to reconstruct, because you can essentially drag all the land masses that border the Atlantic Ocean together and they fit like a crude puzzle. The northwest coast of Africa snuggles right into the east coast of the United States. What’s now called Florida was actually donated from ancestral Africa. It broke off and became attached to North America when Pangea drifted apart.
When Pangea formed, the collisions created the enormous Central Pangean Mountains that cut diagonally across the equator. Some peaks in this range are suspected to have been taller than Mount Everest in the Himalayas. When Pangea broke apart, so did the mountain range. Remnants are found in North America as the Appalachians and Ouachitas, in Africa as the Atlas and Anti-Atlas Mountains, and across Europe from Norway and the Scottish Highlands down to Massif Central in Southern France. Hikers finishing the Appalachian Trail could leave Mount Katahdin and head to Morocco to continue on “The Pangea Traverse,” a multi-continent hiking challenge along the former spine of the Central Pangean Mountains.
Fun evidence of the historically-squished continents exists in some animal and plant lineages. Cypress trees evolved on Pangea, and today species in the cypress family (Cupressaceae) occur on every continent except Antarctica. In Maine we have five: three species of cedar and two junipers.
Marsupials originated in North America pre-Pangea. They moved into modern-day South America and were then isolated when Pangea broke apart. Two descendants of these ancient marsupials then backtracked north when Panama formed about three million years ago. That’s how we have our friend the Virginia Opossum (Didelphis virginiana), the only marsupial found in the United States.
These are just a few threads in the fabric of our planet, a fabric which spans approximately 196.9 million square miles wide and 4.5 billion years deep. It’s a bit dizzying to imagine ourselves as little specks in the vast landscape of organisms and geological forces that make up Earth (we share the planet with 20 quadrillion ants alone!). I find this perspective to be soothing, though. I am but a cog in the machine, in a good way! Together, all the birds and butterflies and trees and whales and humans and tectonic plates and 20 quadrillion ants are chugging along together. We’re adapting, sharing resources, creating food and shelter for one another, and doing our best to survive on this uniquely survivable planet.
