By mid-September, I was starting to hear a lot of reports locally of monarch butterflies in migration, often in locations where those reporting them hadn’t seen monarchs before.
This was the case at my house as well. For the first time in the five years I’ve lived on this heavily wooded property, I spotted one feeding on my Autumn Joy sedum. Monarchs typically favor open fields, where their host plants, in the milkweed family, are more likely to grow. This nonnative sedum, which I’ve dragged from house to house in a concrete container for more than a decade, has large clusters of pink flowers that usually attract butterflies late in the summer and early fall, when many of the natives in my yard have finished blooming. Still, the monarch was a real surprise, as was an American lady, which also showed up for the first time.
The monarch stuck around for three days (assuming it was the same butterfly), so I got a chance to take a few photos and enjoy it before it continued its migration journey to the cool, damp fir forests of central Mexico’s highlands, where it will spend the winter. Likely it will join other monarchs on the way.
A few days later, I noticed several monarchs on some Jerusalem artichoke blossoms in a pasture near Sperryville. Likely also in migration, the butterflies stayed around for a few days before cold weather either sent them to cover or they moved on.
Other sightings of monarchs in migration have been reported on Rappnet, our county Listserv, and from other sources, including the same Tiger Valley resident I wrote about in my last column who had spotted what is likely a rufous hummingbird in her garden. She reported that more than a dozen monarchs suddenly appeared on asters in her garden the last Tuesday (Sept. 27). They disappeared when the rain started that night, but reappeared in even higher numbers (about 18, she said) once sunny days returned.
I also had a monarch show up on my smooth blue asters when the rain ended, likely not the same one that had been on the sedum but rather another migrating through from the north.
Are monarchs actually more plentiful this year, or, with all the publicity about them, are we just more aware of them? It’s hard to know from anecdotal reports. In this year’s Rappahannock butterfly count, held in July — well before the start of the fall migration — only four monarchs were counted, which is the average for the six years of the count. (See more about the results of this year’s butterfly count in an upcoming column.)
Every fall monarch butterflies all over the United States head to cool, damp fir forests of central Mexico’s highlands to spend the winter, with those that spend the summer in the East traveling up to 3,000 miles. According to Monarch Watch, a nonprofit dedicated to conserving the species, monarchs are the only butterflies to make such a long, two-way migration every year — “flying in masses to the same winter roosts, often to the exact same trees.”
The monarchs that migrate south are in the last generation the species produces every summer, sometimes called the “Methusala” generation because they also live longer than earlier generations born in the same year. This generation emerges from chrysalises as adults in late summer or early fall. Rather than mating when they emerge, they save their energy for the long trip south, mating when they return the following spring.
As with many seasonal behaviors, the monarch’s fall migration is driven by shortening days. Their migration through Virginia runs from early September to late October, peaking around the last week of September. Being cold-blooded, migrating monarchs travel only when temperatures are warm enough, roosting together at night to keep each other warm. Once at their destination in Mexico, monarchs roost together by the thousands for protection from cold and wind.
Along the migration journey, monarchs must stop to fuel up, storing fat in their abdomens that must last them through the winter and their return flight back in the spring. According to Monarch Watch, “they actually gain weight during the trip.”
Although some of us who spotted monarchs in our gardens this year have planted milkweed, host plants for the monarch’s caterpillars, migrating adults are more interested in fueling up on the nectar of a variety of flowers that are blooming during their migration. Many of their refueling stops, particularly in the plains states, have been disappearing because of widespread herbicide and pesticide use and habitat loss, so Monarch Watch encourages citizens to plant “Monarch Waystations.”
Researchers are still trying to solve some of the mysteries around this marathon flight, including whether monarchs conserve energy in flight by gliding on air currents and how new generations find the same roosting spot in Mexico every year. Collecting data on migrating species is crucial to their conservation, and several organizations welcome help from citizen scientists.
© 2016 Pam Owen
Helping migrating species
Monarch Watch encourages citizens to help the monarch on its migration by planting “Monarch Waystations,” special gardens plants that provide the butterflies with nectar on their journey and host the caterpillars they produce in the spring. Find out more about these waystations and about monarchs in general at the organization’s website.
To help understand and conserve migrating species, several organizations encourage citizen scientists (anyone with an interest in nature) to also submit their observations. The Journey North collects data on monarchs, hummingbirds, eagles, robins, whooping cranes and gray whales. Report migrating dragonflies to the Dragonfly Partnership. The Cornel Lab of Ornithology’s eBird program collects data on sightings of birds, migrating or otherwise, throughout the year. Both Journey North and eBird have interactive maps showing sightings as they are reported, and the Journey North has lists of sightings.
Eat and be eaten
A large black-and-yellow argiope spider wraps up its prey, a red-footed cannibalfly, another fierce predator (see my Sept. 8 column on this fly). Like many orbweavers (which spin the round, iconic spider webs), these argiopes breed in late summer and early fall, spinning large webs in which to put their egg sacs and to trap prey. The doomed cannibalfly may be the first meal for this spider’s young when they hatch out. Argiopes often inhabit gardens. I found this one had attached its web to branches of a large sage in my herb garden.